2024 |
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| 195. | Jinki Park; Youngin Yoo; Changjae Lee; Dong Ki Yoon; Seong-Ook Park Liquid-Crystal-Based Beam Steering Guided-Wave Metasurface Antenna at Millimeter-Wave Band Journal Article IEEE Antennas and Wireless Propagation Letters, 2024. @article{Park2024, title = {Liquid-Crystal-Based Beam Steering Guided-Wave Metasurface Antenna at Millimeter-Wave Band}, author = {Jinki Park and Youngin Yoo and Changjae Lee and Dong Ki Yoon and Seong-Ook Park}, doi = {10.1109/LAWP.2024.3439587}, year = {2024}, date = {2024-08-06}, journal = {IEEE Antennas and Wireless Propagation Letters}, abstract = {In this paper, we present the design and fabrication of a liquid crystal (LC)-based metasurface antenna for millimeter-wave beam steering applications. Unlike the conventional beamforming systems that rely on phase shifters, our approach harnesses the electrical tunability of LCs. We target a frequency of 34.5 GHz, taking advantage of the pronounced low dielectric loss characteristics exhibited by LCs. The proposed antenna uses a substrate integrated waveguides (SIW) to feed millimeter-wave to metasurface unit cells, and each cell’s radiation is controlled through DC voltage biasing of the LC. The measurement results demonstrate a beam steering range of 120° with a maximum gain of 10.754 dBi and a sidelobe level (SLL) of -11.562 dBc at the boresight.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper, we present the design and fabrication of a liquid crystal (LC)-based metasurface antenna for millimeter-wave beam steering applications. Unlike the conventional beamforming systems that rely on phase shifters, our approach harnesses the electrical tunability of LCs. We target a frequency of 34.5 GHz, taking advantage of the pronounced low dielectric loss characteristics exhibited by LCs. The proposed antenna uses a substrate integrated waveguides (SIW) to feed millimeter-wave to metasurface unit cells, and each cell’s radiation is controlled through DC voltage biasing of the LC. The measurement results demonstrate a beam steering range of 120° with a maximum gain of 10.754 dBi and a sidelobe level (SLL) of -11.562 dBc at the boresight. |
| 194. | Jing Huang; Seung-Joo Jo; Chang-Won Seo; Si-A Lee; Seong-Sik Yoon; Seong-Ook Park Electrical Performance Analysis and Prediction for Complex Mesh based on Model Angles Journal Article IEEE Access, 2024. @article{Huang2024, title = {Electrical Performance Analysis and Prediction for Complex Mesh based on Model Angles}, author = {Jing Huang and Seung-Joo Jo and Chang-Won Seo and Si-A Lee and Seong-Sik Yoon and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2024/08/Electrical_Performance_Analysis_and_Prediction_for_Complex_Mesh_based_on_Model_Angles.pdf}, doi = {10.1109/ACCESS.2024.3431037}, year = {2024}, date = {2024-07-19}, journal = {IEEE Access}, abstract = {The metallic mesh serves as a reflecting surface on deployable reflector antennas for satellites. Electrical properties differ for meshes with different knitting patterns. Also, pattern shapes vary at different tensions due to the elasticity of the mesh. Furthermore, mesh models for electrical performance analysis become more challenging to construct as the mesh knitting patterns become more intricate. A method based on model angles and diagonals is developed in this paper to overcome the aforementioned problems. First, procedures for building a mesh model are described. Then three mesh models of the single Atlas mesh, the single Satin mesh, and the Max mesh are built. The corresponding performance variations are observed and stabilities are compared. Moreover, the wire diameter for the mesh model is determined by measuring the reflectance of the Max mesh and comparing it with simulation results. Afterward, correlations between the reflectivity and incident angles are presented. In addition, the reflectance and transmittance at different incidence angles are measured. Measured results align well with simulated results. It verifies the accuracy of the simulated characteristics and the value of the mesh model in understanding mesh electrical properties.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The metallic mesh serves as a reflecting surface on deployable reflector antennas for satellites. Electrical properties differ for meshes with different knitting patterns. Also, pattern shapes vary at different tensions due to the elasticity of the mesh. Furthermore, mesh models for electrical performance analysis become more challenging to construct as the mesh knitting patterns become more intricate. A method based on model angles and diagonals is developed in this paper to overcome the aforementioned problems. First, procedures for building a mesh model are described. Then three mesh models of the single Atlas mesh, the single Satin mesh, and the Max mesh are built. The corresponding performance variations are observed and stabilities are compared. Moreover, the wire diameter for the mesh model is determined by measuring the reflectance of the Max mesh and comparing it with simulation results. Afterward, correlations between the reflectivity and incident angles are presented. In addition, the reflectance and transmittance at different incidence angles are measured. Measured results align well with simulated results. It verifies the accuracy of the simulated characteristics and the value of the mesh model in understanding mesh electrical properties. |
| 193. | Han-Sol Kim; Jiyeol Meang; Ju-Hye Kim; Dong-Sik Ko; Seong-Ho Seo; Muhammad Tayyab Azim; Seong-Ook Park Miniaturized 24GHz FMCW Radar Leakage Mitigation with Synchronized Subtraction Journal Article IEEE Sensors Journal, 2024. @article{Kim2024, title = {Miniaturized 24GHz FMCW Radar Leakage Mitigation with Synchronized Subtraction}, author = {Han-Sol Kim and Jiyeol Meang and Ju-Hye Kim and Dong-Sik Ko and Seong-Ho Seo and Muhammad Tayyab Azim and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2024/08/Miniaturized_24GHz_FMCW_Radar_Leakage_Mitigation_with_Synchronized_Subtraction-압축됨.pdf}, doi = {10.1109/JSEN.2024.3422397}, year = {2024}, date = {2024-07-11}, journal = {IEEE Sensors Journal}, abstract = {Frequency-modulated continuous wave (FMCW) radar sensors are widely used to measure range, velocity, and target status. As the range of applications for FMCW radar sensors expands, there is an increasing demand for smaller FMCW radar sensors suitable for use in confined spaces. To reduce the form factor of the FMCW radar sensor, the distance between the transmit (Tx) and receive (Rx) antennas is also reduced. This decrease in antenna separation increases the magnitude of the leakage signal transmitted from the Tx to the Rx antenna. However, the leakage signal makes it difficult for the FMCW radar sensor to detect the target by increasing the noise floor. In this article, we present an advanced method to mitigate the increased leakage signal power in the miniaturized FMCW radar sensor. We have fabricated a miniaturized homodyne FMCW radar with consistent leakage signal characteristics. We also propose a method to minimize the influence of the leakage signal by storing the leakage signal characteristics and using the stored data when operating the radar. Experimental results show significant leakage signal power reduction. This technique not only preserves the power of the received target signals but also improves the overall performance of compact FMCW radar sensors. The proposed method provides a basis for miniaturized radar sensors to contribute to various industries by providing an effective solution to the leakage signal problem of small radar technology.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Frequency-modulated continuous wave (FMCW) radar sensors are widely used to measure range, velocity, and target status. As the range of applications for FMCW radar sensors expands, there is an increasing demand for smaller FMCW radar sensors suitable for use in confined spaces. To reduce the form factor of the FMCW radar sensor, the distance between the transmit (Tx) and receive (Rx) antennas is also reduced. This decrease in antenna separation increases the magnitude of the leakage signal transmitted from the Tx to the Rx antenna. However, the leakage signal makes it difficult for the FMCW radar sensor to detect the target by increasing the noise floor. In this article, we present an advanced method to mitigate the increased leakage signal power in the miniaturized FMCW radar sensor. We have fabricated a miniaturized homodyne FMCW radar with consistent leakage signal characteristics. We also propose a method to minimize the influence of the leakage signal by storing the leakage signal characteristics and using the stored data when operating the radar. Experimental results show significant leakage signal power reduction. This technique not only preserves the power of the received target signals but also improves the overall performance of compact FMCW radar sensors. The proposed method provides a basis for miniaturized radar sensors to contribute to various industries by providing an effective solution to the leakage signal problem of small radar technology. |
| 192. | Changjae Lee; Jinki Park; Ye-Eun Chi; Youngin Yoo; Seong-Ook Park; Dong Ki Yoon Ultralow-Voltage Frequency Tunning of Liquid Crystal-Based GHz Antenna via Nanoscratching Method Journal Article Advanced Materials Technologies, 9 (7), pp. 2301859, 2024. @article{Lee2024, title = {Ultralow-Voltage Frequency Tunning of Liquid Crystal-Based GHz Antenna via Nanoscratching Method}, author = {Changjae Lee and Jinki Park and Ye-Eun Chi and Youngin Yoo and Seong-Ook Park and Dong Ki Yoon}, doi = {10.1002/admt.202301859}, year = {2024}, date = {2024-02-12}, journal = {Advanced Materials Technologies}, volume = {9}, number = {7}, pages = {2301859}, abstract = {Liquid crystal (LC)-based radio-frequency (RF) tunable antennas garner attention because of their compact size and minimal heat generation. Exploiting the LC's property to alter the RF permittivity depending on its alignment, voltage-induced orientational switching enables frequency modulation of the radiated wave. To ensure dependable antenna performance, precise control of the initial LC alignment is crucial, which is conventionally achieved by polyimide (PI) coating followed by the rubbing process (PI-rubbing). However, this approach demands high temperature (200 °C) and prolonged processing time (2 h), while also necessitating high voltage for LC reorientation due to induced excessive surface polar anchoring strength. Here, a PI-free-nanoscratching method creating 1D channels is introduced that induces initial LC alignment in a desired direction. The initial orienting capability of the scratched metal surface is superior to that of the PI-rubbed surface. Furthermore, the LC-based antenna employing the nanoscratching method shows a remarkable resonance frequency shift of up to 3 GHz with a low voltage of 2 V. This driving voltage is five times lower than that of antennas using the conventional PI-rubbing method, which can open a new era for the next generation LC-antenna.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Liquid crystal (LC)-based radio-frequency (RF) tunable antennas garner attention because of their compact size and minimal heat generation. Exploiting the LC's property to alter the RF permittivity depending on its alignment, voltage-induced orientational switching enables frequency modulation of the radiated wave. To ensure dependable antenna performance, precise control of the initial LC alignment is crucial, which is conventionally achieved by polyimide (PI) coating followed by the rubbing process (PI-rubbing). However, this approach demands high temperature (200 °C) and prolonged processing time (2 h), while also necessitating high voltage for LC reorientation due to induced excessive surface polar anchoring strength. Here, a PI-free-nanoscratching method creating 1D channels is introduced that induces initial LC alignment in a desired direction. The initial orienting capability of the scratched metal surface is superior to that of the PI-rubbed surface. Furthermore, the LC-based antenna employing the nanoscratching method shows a remarkable resonance frequency shift of up to 3 GHz with a low voltage of 2 V. This driving voltage is five times lower than that of antennas using the conventional PI-rubbing method, which can open a new era for the next generation LC-antenna. |
| 191. | Myoung-Ho Chae; Seong-Ook Park; Seung-Ho Choi; Chae-Taek Choi Reinforcement Learning-Based Counter Fixed-Wing Drone System Using GNSS Deception Journal Article IEEE Access, 12 , pp. 16549 - 16558, 2024. @article{Chae2024, title = {Reinforcement Learning-Based Counter Fixed-Wing Drone System Using GNSS Deception}, author = {Myoung-Ho Chae and Seong-Ook Park and Seung-Ho Choi and Chae-Taek Choi}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2024/08/Reinforcement_Learning-Based_Counter_Fixed-Wing_Drone_System_Using_GNSS_Deception-2-압축됨.pdf}, doi = {10.1109/ACCESS.2024.3358211}, year = {2024}, date = {2024-01-24}, journal = {IEEE Access}, volume = {12}, pages = {16549 - 16558}, abstract = {As drone intrusions into important facilities have increased, research on drone countermeasures has been conducted to counter drones. In this study, we developed a reinforcement learning (RL)-based counter fixed-wing drone system that can respond to fixed-wing drones in autonomous flight with soft kills. The system redirects fixed-wing drones to a designated target position using the global navigation satellite system (GNSS) deception based on the drone’s position and speed measured by RADAR. In this study, to construct an environment for training an RL agent, simplified drone modeling was performed for two types of fixed wing drones, and the RADAR error measured through flight tests was modeled. Subsequently, the Markov decision process (MDP) was defined to enable redirection without prior information regarding fixed-wing drones. After applying the RL agent trained in the defined MDP and environment to the counter fixed-wing drone system, the simulation and flight test results confirmed that redirection was possible for both types of fixed-wing drones.}, keywords = {}, pubstate = {published}, tppubtype = {article} } As drone intrusions into important facilities have increased, research on drone countermeasures has been conducted to counter drones. In this study, we developed a reinforcement learning (RL)-based counter fixed-wing drone system that can respond to fixed-wing drones in autonomous flight with soft kills. The system redirects fixed-wing drones to a designated target position using the global navigation satellite system (GNSS) deception based on the drone’s position and speed measured by RADAR. In this study, to construct an environment for training an RL agent, simplified drone modeling was performed for two types of fixed wing drones, and the RADAR error measured through flight tests was modeled. Subsequently, the Markov decision process (MDP) was defined to enable redirection without prior information regarding fixed-wing drones. After applying the RL agent trained in the defined MDP and environment to the counter fixed-wing drone system, the simulation and flight test results confirmed that redirection was possible for both types of fixed-wing drones. |
2023 |
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| 190. | Young-Geun Kang; Seong-Ook Park A Full-Aperture Frequency Scaling Algorithm for Processing Dechirped Sliding Spotlight SAR Data Journal Article IEEE Access, 11 , pp. 92550-92564, 2023. @article{Kang2023b, title = {A Full-Aperture Frequency Scaling Algorithm for Processing Dechirped Sliding Spotlight SAR Data}, author = {Young-Geun Kang and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2023/09/A-Full-Aperture-Frequency-Scaling-Algorithm-for-Processing-Dechirped-Sliding-Spotlight-SAR-Data.pdf}, doi = {10.1109/ACCESS.2023.3308906}, year = {2023}, date = {2023-08-28}, journal = {IEEE Access}, volume = {11}, pages = {92550-92564}, abstract = {This paper proposes a full-aperture method for processing sliding spotlight synthetic aperture radar (SAR) data with dechirp-on-receive. The frequency scaling algorithm (FSA) efficiently processes the dechirped signals because the range cell migration correction (RCMC) process involves removing the residual video phase. However, the conventional FSA combined with the sub-aperture method is unsuitable for processing sliding mode data because the azimuth extent of the SAR image is limited by the system pulse repetition frequency. In addition, the azimuth compression performance deteriorates as the range displacement increases from the center of the SAR image. To address these problems, we developed a modified full-aperture FSA for sliding mode data processing. A complete signal model of the azimuth convoluted sliding mode data with the dechirp-on-receive is newly derived. Based on the signal model, the frequency scaling factor and azimuth-matched filter have been modified to accurately perform RCMC and azimuth compression. Point target simulations demonstrated two advantages of the proposed algorithm over the conventional sub-aperture approach; One is accurate and consistent azimuth compression performance regardless of range displacements, and the other is wide observable azimuth extent. The practicality of the proposed method is further verified through actual SAR raw data experiments. In addition, it is analyzed that the proposed algorithm is specialized in processing dechirped sliding mode data through a characteristic comparison with various traditional sliding spotlight processing methods.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper proposes a full-aperture method for processing sliding spotlight synthetic aperture radar (SAR) data with dechirp-on-receive. The frequency scaling algorithm (FSA) efficiently processes the dechirped signals because the range cell migration correction (RCMC) process involves removing the residual video phase. However, the conventional FSA combined with the sub-aperture method is unsuitable for processing sliding mode data because the azimuth extent of the SAR image is limited by the system pulse repetition frequency. In addition, the azimuth compression performance deteriorates as the range displacement increases from the center of the SAR image. To address these problems, we developed a modified full-aperture FSA for sliding mode data processing. A complete signal model of the azimuth convoluted sliding mode data with the dechirp-on-receive is newly derived. Based on the signal model, the frequency scaling factor and azimuth-matched filter have been modified to accurately perform RCMC and azimuth compression. Point target simulations demonstrated two advantages of the proposed algorithm over the conventional sub-aperture approach; One is accurate and consistent azimuth compression performance regardless of range displacements, and the other is wide observable azimuth extent. The practicality of the proposed method is further verified through actual SAR raw data experiments. In addition, it is analyzed that the proposed algorithm is specialized in processing dechirped sliding mode data through a characteristic comparison with various traditional sliding spotlight processing methods. |
| 189. | Young-Geun Kang; Seungwoon Park; Eunsung Kim; Kyeongrok Kim; Seong-Ook Park Multichannel Along-Track Interferometric SAR System Implementation Using FMCW Radar Journal Article IEEE Geoscience and Remote Sensing Letters, 20 , pp. 4009405, 2023. @article{Kang2023, title = {Multichannel Along-Track Interferometric SAR System Implementation Using FMCW Radar}, author = {Young-Geun Kang and Seungwoon Park and Eunsung Kim and Kyeongrok Kim and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2023/09/Multichannel-Along-Track-Interferometric-SAR-System-Implementation-Using-FMCW-Radar.pdf}, doi = {10.1109/LGRS.2023.3307187}, year = {2023}, date = {2023-08-21}, journal = {IEEE Geoscience and Remote Sensing Letters}, volume = {20}, pages = {4009405}, abstract = {Along-track synthetic aperture radar interferometry (ATI) systems are used to detect a moving target and to estimate its radial velocity. A dual-channel (single-baseline) ATI system estimates the velocity ambiguously because there are many candidate velocities corresponding to the interferometric phase. To resolve the ambiguity of the estimates, a multichannel (multibaseline) ATI system is required. This letter proposes an efficient implementation technique of a multichannel ATI system by using a frequency-modulated continuous wave (FMCW) radar and an antenna arrangement method considering the inherent bi-static characteristic of FMCW radars. Also, a simple and robust radial velocity estimation algorithm suitable for the proposed system model is presented. The validity of the algorithm is confirmed with simulated ATI results.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Along-track synthetic aperture radar interferometry (ATI) systems are used to detect a moving target and to estimate its radial velocity. A dual-channel (single-baseline) ATI system estimates the velocity ambiguously because there are many candidate velocities corresponding to the interferometric phase. To resolve the ambiguity of the estimates, a multichannel (multibaseline) ATI system is required. This letter proposes an efficient implementation technique of a multichannel ATI system by using a frequency-modulated continuous wave (FMCW) radar and an antenna arrangement method considering the inherent bi-static characteristic of FMCW radars. Also, a simple and robust radial velocity estimation algorithm suitable for the proposed system model is presented. The validity of the algorithm is confirmed with simulated ATI results. |
| 188. | Ye-Eun Chi; Jinki Park; Seong-Ook Park Hybrid Multibeamforming Receiver with High-Precision Beam Steering for Low Earth Orbit Satellite Communication Journal Article IEEE Transactions on Antennas and Propagation, 71 (7), pp. 5695-5707, 2023. @article{Chi2023, title = {Hybrid Multibeamforming Receiver with High-Precision Beam Steering for Low Earth Orbit Satellite Communication}, author = {Ye-Eun Chi and Jinki Park and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2023/09/Hybrid-Multibeamforming-Receiver-With-High-Precision-Beam-Steering-for-Low-Earth-Orbit-Satellite-Communication.pdf}, doi = {10.1109/TAP.2023.3277195}, year = {2023}, date = {2023-05-22}, journal = {IEEE Transactions on Antennas and Propagation}, volume = {71}, number = {7}, pages = {5695-5707}, abstract = {A hybrid multibeamforming receiver for low Earth orbit (LEO) satellite communication in the Ku-band is designed and tested. The proposed receiver is implemented with eight channels to enable the multibeam control. The proposed receiver, including both analog and digital beamforming structures, is capable of multibeam reception using both analog and digital beamforming techniques simultaneously or selectively. Analog beamforming is implemented by employing a local oscillator phase shifter using direct digital synthesis and phase-locked loop (PLL) structures. In digital beamforming, a software-defined radio can control the phase of the signal in the digital baseband. The multibeam received using the proposed hybrid multibeamforming receiver was measured at 11.7 and 12.7 GHz in an anechoic chamber. The phase-control resolutions of analog and digital beamforming were 0.022° and 0.72°, respectively. Analog beam-switching speed is slower than digital beamforming because it depends on the settling time of the PLL circuit, but it has a high phase-control resolution. Therefore, by using analog and digital beamforming when precise beam tilting and fast beam switching are required, respectively, the proposed hybrid multibeamforming is shown to be suitable in accordance with the communication situation.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A hybrid multibeamforming receiver for low Earth orbit (LEO) satellite communication in the Ku-band is designed and tested. The proposed receiver is implemented with eight channels to enable the multibeam control. The proposed receiver, including both analog and digital beamforming structures, is capable of multibeam reception using both analog and digital beamforming techniques simultaneously or selectively. Analog beamforming is implemented by employing a local oscillator phase shifter using direct digital synthesis and phase-locked loop (PLL) structures. In digital beamforming, a software-defined radio can control the phase of the signal in the digital baseband. The multibeam received using the proposed hybrid multibeamforming receiver was measured at 11.7 and 12.7 GHz in an anechoic chamber. The phase-control resolutions of analog and digital beamforming were 0.022° and 0.72°, respectively. Analog beam-switching speed is slower than digital beamforming because it depends on the settling time of the PLL circuit, but it has a high phase-control resolution. Therefore, by using analog and digital beamforming when precise beam tilting and fast beam switching are required, respectively, the proposed hybrid multibeamforming is shown to be suitable in accordance with the communication situation. |
| 187. | Jun Sung Park; Chul Ki Kim; Seong Ook Park A Stretched Deramping Radar Technique for High-Resolution SAR Processing in Ka-Band Using the Extended Integration Time Journal Article IEEE Transactions on Instrumentation and Measurement, 72 , 2023. @article{Park2023, title = {A Stretched Deramping Radar Technique for High-Resolution SAR Processing in Ka-Band Using the Extended Integration Time}, author = {Jun Sung Park and Chul Ki Kim and Seong Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2023/09/A-Stretched-Deramping-Radar-Technique-for-High-Resolution-SAR-Processing-in-Ka-Band-Using-the-Extended-Integration-Time.pdf}, doi = {10.1109/TIM.2023.3264048}, year = {2023}, date = {2023-04-03}, journal = {IEEE Transactions on Instrumentation and Measurement}, volume = {72}, abstract = {To increase the image quality of synthetic aperture radar (SAR) is one of the hot issues for high-performance detection/reconnaissance. With this interest in the SAR technique, it generates various techniques according to the purposed platforms (Auto-SAR, ViSAR, InSAR, and PolSAR). In this article, we introduce high-efficiency and useful techniques, which can be applied to various SAR applications for generating high-quality images in the Ka -band. We proposed the stretched deramping hardware system applicable in the Ka -band, and design the Range-Doppler algorithm which well matches the proposed radar system with the modified signal parameters. Thus, we can extend the integration time of the convolution process in slow time and it leads to the improvement of the SAR image quality. To verify the performance of our proposed technique, we process the practical experiments in conventional outdoor fields. Furthermore, the proposed method is operated on the range Doppler algorithm (RDA), which is mostly used for standard SAR.}, keywords = {}, pubstate = {published}, tppubtype = {article} } To increase the image quality of synthetic aperture radar (SAR) is one of the hot issues for high-performance detection/reconnaissance. With this interest in the SAR technique, it generates various techniques according to the purposed platforms (Auto-SAR, ViSAR, InSAR, and PolSAR). In this article, we introduce high-efficiency and useful techniques, which can be applied to various SAR applications for generating high-quality images in the Ka -band. We proposed the stretched deramping hardware system applicable in the Ka -band, and design the Range-Doppler algorithm which well matches the proposed radar system with the modified signal parameters. Thus, we can extend the integration time of the convolution process in slow time and it leads to the improvement of the SAR image quality. To verify the performance of our proposed technique, we process the practical experiments in conventional outdoor fields. Furthermore, the proposed method is operated on the range Doppler algorithm (RDA), which is mostly used for standard SAR. |
| 186. | Myoung-Ho Chae; Seong-Ook Park; Seung-Ho Choi; Chae-Taek Choi Commercial Fixed-Wing Drone Redirection System using GNSS Deception Journal Article IEEE Transactions on Aerospace and Electronic Systems, 59 (5), pp. 5699-5713, 2023. @article{Chae2023, title = {Commercial Fixed-Wing Drone Redirection System using GNSS Deception}, author = {Myoung-Ho Chae and Seong-Ook Park and Seung-Ho Choi and Chae-Taek Choi}, editor = {As drones become more common today, the threat of reconnaissance or attack drones to core facilities has increased, and countermeasures against them have become essential. In this study, a drone redirection system was proposed to counter illegal intrusion of commercial fixed-wing drones. The drone redirection system was designed as a closed-loop system that automatically redirects the drone to a target position. The main novelty of this study is a proposal for a system that can automatically redirect a commercial fixed-wing drone, which has not been previously explored. We proposed two strategies for redirecting drones. Additionally, simple drone modeling with a path-following algorithm was used to easily model various drones. The drone model was then tuned using flight test data, and the results were compared. Simulations were performed on the designed drone redirection system model to verify the performance of the two proposed strategies for redirecting drones in conjunction with drone fail-detection and innovation check. The performance of the drone redirection system was assessed through flight tests of Remo-M and simulations of Micropilot's hardware-in-the-loop simulator (HWILS). Through simple drone modeling, drone flight tests, and the test results from HWILS, it was proved that the drone redirection system can be applied to various fixed-wing drones.}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2023/09/Commercial-Fixed-Wing-Drone-Redirection-System-using-GNSS-Deception.pdf}, doi = {10.1109/TAES.2023.3264193}, year = {2023}, date = {2023-04-03}, journal = {IEEE Transactions on Aerospace and Electronic Systems}, volume = {59}, number = {5}, pages = {5699-5713}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
2022 |
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| 185. | Laxmikant Minz; Ye-eun Chi; Kyunghoon Kwon; Min-Seon Yun; Young-Chan Moon; Duk-Yong Kim; Seong-Ook Park Utilizing Non-Orthogonal Polarization With Polarization Reuse Technique for 4 × 4 MIMO Capacity Enhancement Journal Article IEEE Access, 10 , pp. 131952-131964, 2022. @article{Minz2022b, title = {Utilizing Non-Orthogonal Polarization With Polarization Reuse Technique for 4 × 4 MIMO Capacity Enhancement}, author = {Laxmikant Minz and Ye-eun Chi and Kyunghoon Kwon and Min-Seon Yun and Young-Chan Moon and Duk-Yong Kim and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2023/03/Utilizing_Non-Orthogonal_Polarization_With_Polarization_Reuse_Technique_for_4__4_MIMO_Capacity_Enhancement.pdf}, doi = {10.1109/ACCESS.2022.3228043}, year = {2022}, date = {2022-12-09}, journal = {IEEE Access}, volume = {10}, pages = {131952-131964}, abstract = {5G communication promises fast and large data stream which requires higher capacity of a cellular wireless network. A higher capacity could be achieved with wider bandwidth and network densification, but they are expensive approaches. Instead, upgrading the wireless network with higher-order Multiple Input Multiple Output (MIMO) antenna system with polarization diversity can inexpensively escalate the peak data rate for higher capacity. We present a 4×4 MIMO cellular network scheme utilizing polarization reuse and using 4 polarization to reform the cellular network from current state of the art of dual polarization 4×4 MIMO scheme. 4 Polarization (vertical, Horizontal, ±45° slant) is used in 2 orthogonal polarization pair form, with a beam-separation among pair, to intensify polarization diversity and maximize the MIMO network channel capacity. This beam-separated polarization reuse technique minimizes the channel correlation which maximizes the probability of four independent data streams (rank 4). The simulated result of the channel capacity with the proposed scheme achieves a 30% higher capacity compared to the baseline configuration of 3-sector 4×4 MIMO. The field trial of the presented network indicates a higher portion of rank 4, supporting four independent data streams in the rich scattering environment of a cellular network.}, keywords = {}, pubstate = {published}, tppubtype = {article} } 5G communication promises fast and large data stream which requires higher capacity of a cellular wireless network. A higher capacity could be achieved with wider bandwidth and network densification, but they are expensive approaches. Instead, upgrading the wireless network with higher-order Multiple Input Multiple Output (MIMO) antenna system with polarization diversity can inexpensively escalate the peak data rate for higher capacity. We present a 4×4 MIMO cellular network scheme utilizing polarization reuse and using 4 polarization to reform the cellular network from current state of the art of dual polarization 4×4 MIMO scheme. 4 Polarization (vertical, Horizontal, ±45° slant) is used in 2 orthogonal polarization pair form, with a beam-separation among pair, to intensify polarization diversity and maximize the MIMO network channel capacity. This beam-separated polarization reuse technique minimizes the channel correlation which maximizes the probability of four independent data streams (rank 4). The simulated result of the channel capacity with the proposed scheme achieves a 30% higher capacity compared to the baseline configuration of 3-sector 4×4 MIMO. The field trial of the presented network indicates a higher portion of rank 4, supporting four independent data streams in the rich scattering environment of a cellular network. |
| 184. | Rao Shahid Aziz; Amit Kumar Singh; Jun-Sung Park; Seong-Ook Park; Slawomir Koziel Compact electromagnetic lens antennas using cascaded metasurfaces for gain enhancement and beam steering applications Journal Article Internatioinal Journal of RF and Microwave Computer-Aided Engieering, 32 (11), pp. e23327, 2022. @article{Aziz2022, title = {Compact electromagnetic lens antennas using cascaded metasurfaces for gain enhancement and beam steering applications}, author = {Rao Shahid Aziz and Amit Kumar Singh and Jun-Sung Park and Seong-Ook Park and Slawomir Koziel}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2023/03/Int-J-RF-Mic-Comp-Aid-Eng-2022-Aziz-Compact-electromagnetic-lens-antennas-using-cascaded-metasurfaces-for-gain.pdf}, doi = {10.1002/mmce.23327}, year = {2022}, date = {2022-07-27}, journal = {Internatioinal Journal of RF and Microwave Computer-Aided Engieering}, volume = {32}, number = {11}, pages = {e23327}, abstract = {Electromagnetic (EM) lens antenna designs using cascaded metasurfaces for gain enhancement and beam steering applications are proposed. Two different lens aperture designs are proposed and populated with aperiodic unit cells of size 0.2λo × 0.2λo. In lens Design 1, the unit cells of different phases are distributed in concentric circular zones, whereas in lens Design 2, the unit cells of different phases are distributed in vertical linear zones on the aperture of the EM lens. Both lenses are composed of two cascaded metasurfaces with an air gap of 0.047λo (where λo = 51.7 mm at 5.8 GHz). For gain enhancement, the metasurfaces are positioned at an optimum focal distance, f = 0.61λo above source patch antenna (f/D = 0.3). Beam steering is accomplished by phase transformation of the source antenna, which can be realized by mechanically sliding the passive metasurfaces in one direction (i.e., ±x-direction) above the source antenna. The prototype of the two proposed lenses are fabricated and tested. The measured peak boresight gain obtained from Design 1 and 2 are 14.98 and 15.12 dBi, respectively. The experimental results show −25° to +25° and −27° to +27° beam steering range for Design 1 and 2, respectively, with a little gain degradation at other angles.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Electromagnetic (EM) lens antenna designs using cascaded metasurfaces for gain enhancement and beam steering applications are proposed. Two different lens aperture designs are proposed and populated with aperiodic unit cells of size 0.2λo × 0.2λo. In lens Design 1, the unit cells of different phases are distributed in concentric circular zones, whereas in lens Design 2, the unit cells of different phases are distributed in vertical linear zones on the aperture of the EM lens. Both lenses are composed of two cascaded metasurfaces with an air gap of 0.047λo (where λo = 51.7 mm at 5.8 GHz). For gain enhancement, the metasurfaces are positioned at an optimum focal distance, f = 0.61λo above source patch antenna (f/D = 0.3). Beam steering is accomplished by phase transformation of the source antenna, which can be realized by mechanically sliding the passive metasurfaces in one direction (i.e., ±x-direction) above the source antenna. The prototype of the two proposed lenses are fabricated and tested. The measured peak boresight gain obtained from Design 1 and 2 are 14.98 and 15.12 dBi, respectively. The experimental results show −25° to +25° and −27° to +27° beam steering range for Design 1 and 2, respectively, with a little gain degradation at other angles. |
| 183. | Young-Geun Kang; Dae-Hwan Jung; Goo-Hwan Shin; Chul-Ki Kim; Seong-Ook Park A Study on the Feasibility of Stop-and-Go Approximation in FMCW SAR Journal Article Journal of Electromagnetic Engineering and Science, 22 (3), pp. 210-217, 2022. @article{Kang2022d, title = {A Study on the Feasibility of Stop-and-Go Approximation in FMCW SAR}, author = {Young-Geun Kang and Dae-Hwan Jung and Goo-Hwan Shin and Chul-Ki Kim and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2022/06/jees-2022-3-r-79.pdf}, doi = {10.26866/jees.2022.3.r.79}, year = {2022}, date = {2022-04-20}, journal = {Journal of Electromagnetic Engineering and Science}, volume = {22}, number = {3}, pages = {210-217}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 182. | Young-Geun Kang; Chul-Ki Kim; Seong-Ook Park Ocean Image Formation Algorithm Using Altimeter Data for Next Generation Satellite SAR Journal Article Journal of Electromagnetic Engineering and Science, 22 (2), pp. 85-94, 2022. @article{Kang2022, title = {Ocean Image Formation Algorithm Using Altimeter Data for Next Generation Satellite SAR}, author = {Young-Geun Kang and Chul-Ki Kim and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2022/05/jees-2022-2-r-64.pdf}, doi = {10.26866/jees.2022.2.r.64}, year = {2022}, date = {2022-03-31}, journal = {Journal of Electromagnetic Engineering and Science}, volume = {22}, number = {2}, pages = {85-94}, abstract = {Synthetic aperture radar (SAR) obtains two-dimensional images of the Earth’s surface. Spatial resolution is one of the most important factors in evaluating SAR performance. Therefore, high operating frequencies are preferred for obtaining high resolution images. In fact, Ku-band and Ka-band are used in the automobile SAR (Auto-SAR) and the aircraft SAR (Airborne-SAR). However, the operating frequencies of the satellite SAR (Spaceborne-SAR) are limited to the X-band because of the wide Doppler frequency band caused by the satellite’s high velocity. To overcome this frequency limitation in satellite SAR, we propose a low-complexity SAR algorithm that forms images of the ocean using satellite altimeter data with an operating frequency of the Ku-band (13.575 GHz). The algorithm requires the burst mode pulse transmission technique frequently used in SAR altimeters. To validate the proposed algorithm as being suitable for ocean image formation, point target simulation and analysis are performed, and some quantitative results are provided.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Synthetic aperture radar (SAR) obtains two-dimensional images of the Earth’s surface. Spatial resolution is one of the most important factors in evaluating SAR performance. Therefore, high operating frequencies are preferred for obtaining high resolution images. In fact, Ku-band and Ka-band are used in the automobile SAR (Auto-SAR) and the aircraft SAR (Airborne-SAR). However, the operating frequencies of the satellite SAR (Spaceborne-SAR) are limited to the X-band because of the wide Doppler frequency band caused by the satellite’s high velocity. To overcome this frequency limitation in satellite SAR, we propose a low-complexity SAR algorithm that forms images of the ocean using satellite altimeter data with an operating frequency of the Ku-band (13.575 GHz). The algorithm requires the burst mode pulse transmission technique frequently used in SAR altimeters. To validate the proposed algorithm as being suitable for ocean image formation, point target simulation and analysis are performed, and some quantitative results are provided. |
| 181. | Chul-Ki Kim; Mi-Young Park; Goo-Hwan Shin; Seong-Ook Park An Improved Technique for Single-Channel Video-SAR Based on Fractional Fourier Transform Journal Article IEEE Transactions on Aerospace and Electronic Systems, 2022. @article{Kim2022, title = {An Improved Technique for Single-Channel Video-SAR Based on Fractional Fourier Transform}, author = {Chul-Ki Kim and Mi-Young Park and Goo-Hwan Shin and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2023/10/An-Improved-Technique-for-Single-Channel-Video-SAR-Based-on-Fractional-Fourier-Transform.pdf}, doi = {10.1109/TAES.2022.3157657}, year = {2022}, date = {2022-03-08}, journal = {IEEE Transactions on Aerospace and Electronic Systems}, abstract = {In the field of Synthetic Aperture Radar (SAR), a lot of researchers have tried to study an improved application beyond the conventional 2D image. Video-SAR (ViSAR) is one of the hot-issue in the SAR application. The main purpose of ViSAR is to monitor various targets in the area of interest in time order. It can offer video images to detect not only the fixed target but also the moving target. For the signal processing of ViSAR, this paper introduces the improved performance by the Doppler shifting technique with Fractional Fourier Transform (FrFT). And also, it shows that the proposed method can separate the unexpected signal of the moving target within each frame of single-channel ViSAR. Furthermore, the overall algorithm can increase efficiency and reliability in ViSAR processing. To verify the improvement of our method, we carry out the practical experiments by an X-band chirp pulse SAR system, mounted on an airplane.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In the field of Synthetic Aperture Radar (SAR), a lot of researchers have tried to study an improved application beyond the conventional 2D image. Video-SAR (ViSAR) is one of the hot-issue in the SAR application. The main purpose of ViSAR is to monitor various targets in the area of interest in time order. It can offer video images to detect not only the fixed target but also the moving target. For the signal processing of ViSAR, this paper introduces the improved performance by the Doppler shifting technique with Fractional Fourier Transform (FrFT). And also, it shows that the proposed method can separate the unexpected signal of the moving target within each frame of single-channel ViSAR. Furthermore, the overall algorithm can increase efficiency and reliability in ViSAR processing. To verify the improvement of our method, we carry out the practical experiments by an X-band chirp pulse SAR system, mounted on an airplane. |
2021 |
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| 180. | Kyei Anim; Patrick Danuor; Seong-Ook Park; Young-Bae Jung High-Efficiency Broadband Planar Array Antenna with Suspended Microstrip Slab for X-Band SAR Onboard Small Satellites Journal Article Sensors, 22 (1), pp. 252, 2021. @article{Anim2021, title = {High-Efficiency Broadband Planar Array Antenna with Suspended Microstrip Slab for X-Band SAR Onboard Small Satellites}, author = {Kyei Anim and Patrick Danuor and Seong-Ook Park and Young-Bae Jung}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2022/01/High-Efficiency-Broadband-Planar-Array-Antenna-with-Suspended-Microstrip-Slab-for-X-Band-SAR-Onboard-Small-Satellites.pdf}, doi = {10.3390/s22010252}, year = {2021}, date = {2021-12-30}, journal = {Sensors}, volume = {22}, number = {1}, pages = {252}, abstract = {In this paper, a high efficiency broadband planar array antenna is developed at X-band for synthetic aperture radar (SAR) on small satellites. The antenna is based on a multi-layer element structure consisting of two dielectric substrates made of Taconic TLY-5 and three copper layers (i.e., the parasitic patch (top layer), the active patch (middle layer), and the ground plane (bottom layer)). The parasitic patch resides on the bottom surface of the upper TLY-5 substrate while the active patch is printed on the top surface of the lower substrate. A Rohacell foam material is sandwiched between the top layer and the middle layer to separate the two dielectric substrates in order to achieve high directivity, wideband, and to keep the antenna weight to a minimum as required by the SAR satellite application. To satisfy the required size of the antenna panel for the small SAR satellite, an asymmetric corporate feeding network (CFN) is designed to feed a 12 × 16 planar array antenna. However, it was determined that the first corporate feed junction at the center of the CFN, where higher amplitudes of the input signal are located, contributes significantly to the leaky wave emission, which degrades the radiation efficiency and increases the sidelobe level. Thus, a suspended microstrip slab, which is simply a wide and long microstrip line, is designed and positioned on the top layer directly above that feed junction to prevent the leaky waves from radiating. The experimental results of the antenna show good agreement with the simulated ones, achieving an impedance bandwidth of 12.4% from 9.01 to 10.20 GHz and a high gain above 28 dBi. The antenna efficiency estimated from the gain and directivity eclipses 51.34%.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper, a high efficiency broadband planar array antenna is developed at X-band for synthetic aperture radar (SAR) on small satellites. The antenna is based on a multi-layer element structure consisting of two dielectric substrates made of Taconic TLY-5 and three copper layers (i.e., the parasitic patch (top layer), the active patch (middle layer), and the ground plane (bottom layer)). The parasitic patch resides on the bottom surface of the upper TLY-5 substrate while the active patch is printed on the top surface of the lower substrate. A Rohacell foam material is sandwiched between the top layer and the middle layer to separate the two dielectric substrates in order to achieve high directivity, wideband, and to keep the antenna weight to a minimum as required by the SAR satellite application. To satisfy the required size of the antenna panel for the small SAR satellite, an asymmetric corporate feeding network (CFN) is designed to feed a 12 × 16 planar array antenna. However, it was determined that the first corporate feed junction at the center of the CFN, where higher amplitudes of the input signal are located, contributes significantly to the leaky wave emission, which degrades the radiation efficiency and increases the sidelobe level. Thus, a suspended microstrip slab, which is simply a wide and long microstrip line, is designed and positioned on the top layer directly above that feed junction to prevent the leaky waves from radiating. The experimental results of the antenna show good agreement with the simulated ones, achieving an impedance bandwidth of 12.4% from 9.01 to 10.20 GHz and a high gain above 28 dBi. The antenna efficiency estimated from the gain and directivity eclipses 51.34%. |
| 179. | Dong-Chan Kim; Ye-eun Chi; Junhyeong Park; Laxmikant Minz; Seong-Ook Park High Resolution Digital Beamforming Receiver Using DDS-PLL Signal Generator for 5G Mobile Communication Journal Article IEEE Transactions on Antennas and Propagation, 2021. @article{Kim2021e, title = {High Resolution Digital Beamforming Receiver Using DDS-PLL Signal Generator for 5G Mobile Communication}, author = {Dong-Chan Kim and Ye-eun Chi and Junhyeong Park and Laxmikant Minz and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2022/01/High-Resolution-Digital-Beamforming-Receiver-Using-DDS-PLL-Signal-Generator-for-5G-Mobile-Communication.pdf}, doi = {10.1109/TAP.2021.3111334}, year = {2021}, date = {2021-09-15}, journal = {IEEE Transactions on Antennas and Propagation}, abstract = {This paper presents a signal generator and a Digital Beamforming Receiver (DBR) with high phase control resolution and high beam control resolution, respectively. The signal generator is designed based on a Direct Digital Synthesizer (DDS) and a Phase Lock Loop (PLL). In the DDS-PLL signal generator, the conventional divider in PLL is replaced with a mixer, comb generator, and a doubler to utilize high phase control resolution of DDS (14bit, 0.022°) as it is and to synchronize the DDS-PLL signal generator with the entire system. In the DBR, the output signals of the DDS-PLL signal generators are used as the second Local Oscillator (LO) signal, and the beamforming technique is implemented through the change of the phase of the second LO signals. Also, for sophisticated beamforming, all signal generator components in the DBR are synchronized for generating same and fixed frequency and phase. Finally, the DBR has the same phase control resolution as the DDS, and the phase of each chain of the DBR can be adjusted up to 0.022° (14 bit). The DBR using the DDS-PLL signal generator is designed and fabricated. The DBR consists of a 1X8 array Tapered Slot Antenna (TSA) part, a 1st and 2nd frequency conversion part, a 1X8 data acquisition and combiner part, DDS-PLL signal generator part, and a reference signal generator part. The phase control performance of the DBR was verified by measuring the phase change of the chain in the DBR according to the DDS phase change. Also, to verify the beamforming performance of the DBR with high beam control resolution, the radiation pattern of the DBR when the angle of the main lobe was 0°, 0.2°, 0.4°, 15°, and 30° was measured in the 28GHz band. At the main lobe, the gain error is within 1dB and the beam angle error is within 0.2 degrees. The simulation results are in good agreement with the measured results. A high resolution beamforming performance is achieved in the DBR using the DDS-PLL signal generator.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper presents a signal generator and a Digital Beamforming Receiver (DBR) with high phase control resolution and high beam control resolution, respectively. The signal generator is designed based on a Direct Digital Synthesizer (DDS) and a Phase Lock Loop (PLL). In the DDS-PLL signal generator, the conventional divider in PLL is replaced with a mixer, comb generator, and a doubler to utilize high phase control resolution of DDS (14bit, 0.022°) as it is and to synchronize the DDS-PLL signal generator with the entire system. In the DBR, the output signals of the DDS-PLL signal generators are used as the second Local Oscillator (LO) signal, and the beamforming technique is implemented through the change of the phase of the second LO signals. Also, for sophisticated beamforming, all signal generator components in the DBR are synchronized for generating same and fixed frequency and phase. Finally, the DBR has the same phase control resolution as the DDS, and the phase of each chain of the DBR can be adjusted up to 0.022° (14 bit). The DBR using the DDS-PLL signal generator is designed and fabricated. The DBR consists of a 1X8 array Tapered Slot Antenna (TSA) part, a 1st and 2nd frequency conversion part, a 1X8 data acquisition and combiner part, DDS-PLL signal generator part, and a reference signal generator part. The phase control performance of the DBR was verified by measuring the phase change of the chain in the DBR according to the DDS phase change. Also, to verify the beamforming performance of the DBR with high beam control resolution, the radiation pattern of the DBR when the angle of the main lobe was 0°, 0.2°, 0.4°, 15°, and 30° was measured in the 28GHz band. At the main lobe, the gain error is within 1dB and the beam angle error is within 0.2 degrees. The simulation results are in good agreement with the measured results. A high resolution beamforming performance is achieved in the DBR using the DDS-PLL signal generator. |
| 178. | Ashish Kumar Singh; Kyung-Bin Bae; Seong-Ook Park NLFM pulse radar for drone detection using predistortion technique Journal Article Journal of Electromagnetic Waves and Applications, 35 (3), pp. 416 - 429, 2021. @article{Singh2021, title = {NLFM pulse radar for drone detection using predistortion technique}, author = {Ashish Kumar Singh and Kyung-Bin Bae and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2021/03/NLFM-pulse-radar-for-drone-detection-using-predistortion-technique-3.pdf}, doi = {10.1080/09205071.2020.1844598}, year = {2021}, date = {2021-02-11}, journal = {Journal of Electromagnetic Waves and Applications}, volume = {35}, number = {3}, pages = {416 - 429}, abstract = {The development of radar technology for the detection of small drones is getting attention of researchers. In this work, the detection of drones using Ku-band radar system has been discussed. We have utilized the advantage of nonlinear frequency modulation (NLFM) waveform for the suppression of range sidelobes. The performance and sensitivity of a radar system can be related with the linearity of system response. Here, we have made an effort to minimize non-linearity in the radar system response by using digital predistortion method. In this method, amplitude weighting coefficients have been calculated based on the received data. We have used FPGA-based transceiver for intermediate frequency (IF) signal generation and data acquisition, along with Ku-band up-down converters. The radar system was first calibrated for desired frequency band using amplitude predistortion method. In this article, experiment results for the detection of single drone and two drones using NLFM pulse signal are presented.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The development of radar technology for the detection of small drones is getting attention of researchers. In this work, the detection of drones using Ku-band radar system has been discussed. We have utilized the advantage of nonlinear frequency modulation (NLFM) waveform for the suppression of range sidelobes. The performance and sensitivity of a radar system can be related with the linearity of system response. Here, we have made an effort to minimize non-linearity in the radar system response by using digital predistortion method. In this method, amplitude weighting coefficients have been calculated based on the received data. We have used FPGA-based transceiver for intermediate frequency (IF) signal generation and data acquisition, along with Ku-band up-down converters. The radar system was first calibrated for desired frequency band using amplitude predistortion method. In this article, experiment results for the detection of single drone and two drones using NLFM pulse signal are presented. |
| 177. | Junhyeong Park; Dae-Hwan Jung; Seong-Ook Park Strategic method of determining parameter values in frequency modulated continuous wave radar for low noise floor over middle‐long range Journal Article Microwave and Optical Technology Letters, 2021. @article{Park2021b, title = {Strategic method of determining parameter values in frequency modulated continuous wave radar for low noise floor over middle‐long range}, author = {Junhyeong Park and Dae-Hwan Jung and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2021/03/mop.32805.pdf}, doi = {10.1002/mop.32805}, year = {2021}, date = {2021-02-03}, journal = {Microwave and Optical Technology Letters}, abstract = {Heterodyne architecture has been frequently chosen to resolve the problem of dc offset in frequency modulated continuous wave (FMCW) radar. However, heterodyne FMCW radars use different local oscillators, resulting in uncorrelated phase noise (UPN) in beat signals. Therefore, the inherent leakage signal in the heterodyne FMCW radar also has UPN and raises the noise floor in the power spectrum. In this letter, we propose a strategic decision method for parameter values in the heterodyne FMCW radar to achieve a low noise floor over the middle‐long range. In addition, we experimentally discover the relation between the UPN and the processing gain for the first time. Based on this relation, we devise an exact formula for the degree of improvement achieved due to the proposed strategic decision method. Experimental results confirm the devised formula and show that the proposed method significantly reduces the noise floor over the middle‐long range.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Heterodyne architecture has been frequently chosen to resolve the problem of dc offset in frequency modulated continuous wave (FMCW) radar. However, heterodyne FMCW radars use different local oscillators, resulting in uncorrelated phase noise (UPN) in beat signals. Therefore, the inherent leakage signal in the heterodyne FMCW radar also has UPN and raises the noise floor in the power spectrum. In this letter, we propose a strategic decision method for parameter values in the heterodyne FMCW radar to achieve a low noise floor over the middle‐long range. In addition, we experimentally discover the relation between the UPN and the processing gain for the first time. Based on this relation, we devise an exact formula for the degree of improvement achieved due to the proposed strategic decision method. Experimental results confirm the devised formula and show that the proposed method significantly reduces the noise floor over the middle‐long range. |
| 176. | Junhyeong Park; Jun-Sung Park; Kyung-Bin Bae; Seong-Ook Park Advanced stationary point concentration technique for leakage mitigation and small drone detection with FMCW radar Journal Article IEEE Transactions on Microwave Theory and Techniques, 69 (3), pp. 1791 - 1804, 2021. @article{Park2021, title = {Advanced stationary point concentration technique for leakage mitigation and small drone detection with FMCW radar}, author = {Junhyeong Park and Jun-Sung Park and Kyung-Bin Bae and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2021/03/09339993-4.pdfhttp://ma.kaist.ac.kr/wp-content/uploads/2021/03/09339993-5.pdf}, doi = {10.1109/TMTT.2021.3052190}, year = {2021}, date = {2021-01-28}, journal = {IEEE Transactions on Microwave Theory and Techniques}, volume = {69}, number = {3}, pages = {1791 - 1804}, abstract = {With the increase in threats posed by small drones, the development of radars to detect such drones has become a key necessity. In earlier studies, we proposed the stationary point concentration (SPC) technique for small drone detection using frequency-modulated continuous-wave (FMCW) radar. The SPC technique is a novel approach for mitigating leakage, which is an inherent problem in FMCW radar. The SPC technique improves the signal-to-noise ratio of small drones by reducing the noise floor and provides accurate distance and velocity information of such drones. However, this technique has shortcomings in its realization. In this article, we present the drawbacks of this technique and propose an advanced SPC (A-SPC) technique. The proposed technique can overcome the drawbacks of the SPC technique while implementing the benefits of the SPC technique. The experimental results verify the proposed A-SPC technique and demonstrate its robustness and usefulness.}, keywords = {}, pubstate = {published}, tppubtype = {article} } With the increase in threats posed by small drones, the development of radars to detect such drones has become a key necessity. In earlier studies, we proposed the stationary point concentration (SPC) technique for small drone detection using frequency-modulated continuous-wave (FMCW) radar. The SPC technique is a novel approach for mitigating leakage, which is an inherent problem in FMCW radar. The SPC technique improves the signal-to-noise ratio of small drones by reducing the noise floor and provides accurate distance and velocity information of such drones. However, this technique has shortcomings in its realization. In this article, we present the drawbacks of this technique and propose an advanced SPC (A-SPC) technique. The proposed technique can overcome the drawbacks of the SPC technique while implementing the benefits of the SPC technique. The experimental results verify the proposed A-SPC technique and demonstrate its robustness and usefulness. |
2020 |
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| 175. | Hyun-Seong Kang; Byung Kwan Kim; Jun-Sung Park; Jun-Seuk Suh; Seong-Ook Park Drone Elevation Angle Classification Based on Convolutional Neural Network With Micro-Doppler of Multipolarization Journal Article IEEE Geoscience and Remote Sensing Letters, 2020. @article{Kang2020c, title = {Drone Elevation Angle Classification Based on Convolutional Neural Network With Micro-Doppler of Multipolarization}, author = {Hyun-Seong Kang and Byung Kwan Kim and Jun-Sung Park and Jun-Seuk Suh and Seong-Ook Park}, doi = {10.1109/LGRS.2020.3030113}, year = {2020}, date = {2020-11-02}, journal = {IEEE Geoscience and Remote Sensing Letters}, abstract = {Multipolarizations of micro-Doppler signature (MDS) were combined to classify the elevation angle of a drone by a convolutional neural network (CNN). We classified the drone's elevation angle based on the MDS, which depends on the elevation angle of the drone. To enhance the classification accuracy, we utilized micro-Doppler from multiple polarized radar signals. We utilized and analyzed four different polarizations for the receiver, namely, vertical/horizontal/right-handed circular polarization (RHCP)/left-handed circular polarization (LHCP), while the polarization for the transmitter was vertical. The four receivers with different polarizations were fully synchronized with Tx for accurate MDS measurement for each polarization. The radar data received from the multiple polarizations were combined for the classification algorithm based on CNN. The classification rate of the elevation angles of a drone was improved from 84.745% to 97.9% compared to a single polarization by using multiple polarizations.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Multipolarizations of micro-Doppler signature (MDS) were combined to classify the elevation angle of a drone by a convolutional neural network (CNN). We classified the drone's elevation angle based on the MDS, which depends on the elevation angle of the drone. To enhance the classification accuracy, we utilized micro-Doppler from multiple polarized radar signals. We utilized and analyzed four different polarizations for the receiver, namely, vertical/horizontal/right-handed circular polarization (RHCP)/left-handed circular polarization (LHCP), while the polarization for the transmitter was vertical. The four receivers with different polarizations were fully synchronized with Tx for accurate MDS measurement for each polarization. The radar data received from the multiple polarizations were combined for the classification algorithm based on CNN. The classification rate of the elevation angles of a drone was improved from 84.745% to 97.9% compared to a single polarization by using multiple polarizations. |
| 174. | Byung Kwan Kim; Hyun-Seong Kang; Seongwook Lee; Seong-Ook Park Improved Drone Classification Using Polarimetric Merged-Doppler Images Journal Article IEEE Geoscience and Remote Sensing Letters, 2020. @article{Kim2020f, title = {Improved Drone Classification Using Polarimetric Merged-Doppler Images}, author = {Byung Kwan Kim and Hyun-Seong Kang and Seongwook Lee and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2021/03/09158523.pdf}, doi = {10.1109/LGRS.2020.3011114}, year = {2020}, date = {2020-08-04}, journal = {IEEE Geoscience and Remote Sensing Letters}, abstract = {We propose a drone classification method for polarimetric radar, based on convolutional neural network (CNN) and image processing methods. The proposed method improves drone classification accuracy when the micro-Doppler signature is very weak by the aspect angle. To utilize received polarimetric signal, we propose a novel image structure for three-channel image classification CNN. To reduce the size of data from four different polarization while securing high classification accuracy, an image processing method and structure are introduced. The data set is prepared for a three type of drone, with a polarimetric Ku-band frequency modulated continuous wave (FMCW) radar system. Proposed method is tested and verified in an anechoic chamber environment for fast evaluation. A famous CNN structure, GoogLeNet, is used to evaluate the effect of the proposed radar preprocessing. The result showed that the proposed method improved the accuracy from 89.9% to 99.8%, compared with single polarized micro-Doppler image. We compared the result from the proposed method with conventional polarimetric radar image structure and achieved similar accuracy while having half of full polarimetric data.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We propose a drone classification method for polarimetric radar, based on convolutional neural network (CNN) and image processing methods. The proposed method improves drone classification accuracy when the micro-Doppler signature is very weak by the aspect angle. To utilize received polarimetric signal, we propose a novel image structure for three-channel image classification CNN. To reduce the size of data from four different polarization while securing high classification accuracy, an image processing method and structure are introduced. The data set is prepared for a three type of drone, with a polarimetric Ku-band frequency modulated continuous wave (FMCW) radar system. Proposed method is tested and verified in an anechoic chamber environment for fast evaluation. A famous CNN structure, GoogLeNet, is used to evaluate the effect of the proposed radar preprocessing. The result showed that the proposed method improved the accuracy from 89.9% to 99.8%, compared with single polarized micro-Doppler image. We compared the result from the proposed method with conventional polarimetric radar image structure and achieved similar accuracy while having half of full polarimetric data. |
| 173. | Hyunseong Kang; Kyung-Bin Bae; Myung-Hun Jeong; Seong-Ook Park Measurement and Analysis of Radiation Leakage From a GPS Module for the Detection of Drones Journal Article IEEE Antennas and Wireless Propagation Letters, 19 (9), pp. 1610 - 1614, 2020. @article{Kang2020b, title = {Measurement and Analysis of Radiation Leakage From a GPS Module for the Detection of Drones}, author = {Hyunseong Kang and Kyung-Bin Bae and Myung-Hun Jeong and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2020/09/Measurement-and-Analysis-of-Radiation-Leakage-From-a-GPS-Module-for-the-Detection-of-Drones.pdf}, doi = {10.1109/LAWP.2020.3011851}, year = {2020}, date = {2020-07-24}, journal = {IEEE Antennas and Wireless Propagation Letters}, volume = {19}, number = {9}, pages = {1610 - 1614}, abstract = {Radiation leakage of a global positioning system (GPS) module was investigated for a drone detection system by measuring the attenuation effect and long-range detection on the outside of a building. The GPS module consisting of the radio frequency components is essential to control the flight of a drone. There is an unavoidable leakage in the GPS module during operation, and the leakage signal from the GPS module was analyzed and detected with a high-sensitivity receiver. To analyze the leakage from the GPS module during operation, we obtained the whole frequencies of leakage signals and the radiation pattern of a drone with the GPS module in an anechoic chamber. From the data, we measured the leakage signals in an outdoor space. Through outdoor measurement, it was confirmed that the theoretical attenuation effect was consistent with the measured value with a distance variation. Finally, the GPS leakage in the drone was measured up to 950 m with a high signal-to-noise ratio (SNR) of 25 dB.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Radiation leakage of a global positioning system (GPS) module was investigated for a drone detection system by measuring the attenuation effect and long-range detection on the outside of a building. The GPS module consisting of the radio frequency components is essential to control the flight of a drone. There is an unavoidable leakage in the GPS module during operation, and the leakage signal from the GPS module was analyzed and detected with a high-sensitivity receiver. To analyze the leakage from the GPS module during operation, we obtained the whole frequencies of leakage signals and the radiation pattern of a drone with the GPS module in an anechoic chamber. From the data, we measured the leakage signals in an outdoor space. Through outdoor measurement, it was confirmed that the theoretical attenuation effect was consistent with the measured value with a distance variation. Finally, the GPS leakage in the drone was measured up to 950 m with a high signal-to-noise ratio (SNR) of 25 dB. |
| 172. | Dae-Hwan Jung; Do-Hoon Kim; Muhammad Tayyab Azim; Junhyeong Park; Seong-Ook Park A Novel Signal Processing Technique for Ku-Band Automobile FMCW Fully Polarimetric SAR System Using Triangular LFM Journal Article IEEE Transactions on Instrumentation and Measurement, 2020. @article{Jung2020, title = {A Novel Signal Processing Technique for Ku-Band Automobile FMCW Fully Polarimetric SAR System Using Triangular LFM}, author = {Dae-Hwan Jung and Do-Hoon Kim and Muhammad Tayyab Azim and Junhyeong Park and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2021/03/09146876-2.pdf}, doi = {https://doi.org/10.1109/TIM.2020.3011601}, year = {2020}, date = {2020-07-24}, journal = {IEEE Transactions on Instrumentation and Measurement}, abstract = {This article presents a novel signal technique for Ku-band automobile frequency-modulated continuous-wave fully polarimetric synthetic aperture radar (FMCW PolSAR) system using triangular linear frequency modulation (LFM). Our proposed system shows the first utilizations of triangular LFM for an FMCW PolSAR. The proposed signal processing algorithm is based on the range Doppler algorithm (RDA). We developed an FMCW PolSAR system that transmits triangular LFM signals, which are used less frequently than sawtooth LFM in an SAR sensor. Using a theoretical background, we describe its configuration and how it works. We propose the novel processing solution, which forms two kinds of single-polarization images from a raw data set and is suitable for our system. We obtained all four kinds of single-polarization images from two raw data sets while using the triangular LFM. In comparison, when using sawtooth LFM, we obtained the four images from four raw data sets by repeating the RDA four times. The proposed method simplifies the FMCW PolSAR system configuration and the processing algorithm. We collected FMCW PolSAR raw data from an experimentally equipped automobile while maintaining a constant speed on a highway. The proposed algorithm and system were validated by processing a high-resolution FMCW PolSAR image.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This article presents a novel signal technique for Ku-band automobile frequency-modulated continuous-wave fully polarimetric synthetic aperture radar (FMCW PolSAR) system using triangular linear frequency modulation (LFM). Our proposed system shows the first utilizations of triangular LFM for an FMCW PolSAR. The proposed signal processing algorithm is based on the range Doppler algorithm (RDA). We developed an FMCW PolSAR system that transmits triangular LFM signals, which are used less frequently than sawtooth LFM in an SAR sensor. Using a theoretical background, we describe its configuration and how it works. We propose the novel processing solution, which forms two kinds of single-polarization images from a raw data set and is suitable for our system. We obtained all four kinds of single-polarization images from two raw data sets while using the triangular LFM. In comparison, when using sawtooth LFM, we obtained the four images from four raw data sets by repeating the RDA four times. The proposed method simplifies the FMCW PolSAR system configuration and the processing algorithm. We collected FMCW PolSAR raw data from an experimentally equipped automobile while maintaining a constant speed on a highway. The proposed algorithm and system were validated by processing a high-resolution FMCW PolSAR image. |
| 171. | Chul-Ki Kim; Muhammad Tayyab Azim; Ashish Kumar Singh; Seong-Ook Park Doppler Shifting Technique for Generating Multi-Frames of Video SAR via Sub-Aperture Signal Processing Journal Article IEEE Transactions on Signal Processing, 68 , pp. 3990 - 4001, 2020. @article{Kim2020e, title = {Doppler Shifting Technique for Generating Multi-Frames of Video SAR via Sub-Aperture Signal Processing}, author = {Chul-Ki Kim and Muhammad Tayyab Azim and Ashish Kumar Singh and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2020/09/Doppler-Shifting-Technique-for-Generating-Multi-Frames-of-Video-SAR-via-Sub-Aperture-Signal-Processing.pdf}, doi = {10.1109/TSP.2020.3006749}, year = {2020}, date = {2020-07-02}, journal = {IEEE Transactions on Signal Processing}, volume = {68}, pages = {3990 - 4001}, abstract = {The signal processing technologies of synthetic aperture radar (SAR) have been vastly studied as diverse measurement modes for various applications. One of the technologies is Video-SAR (ViSAR). It is a land-imaging mode where a sequence of images is continuously formed on the spotlight mode. We propose a new signal processing method to generate the multi-frames of ViSAR using Doppler shifting technique via sub-aperture processing. The method is based on our designed wide-angle antenna, which is a corrugated horn shape with low side lobe and Gaussian beam pattern. This wide-angle antenna receives a wide Doppler band along the azimuth direction. Based on the characteristics of the antenna, we separate the wide Doppler band into each chirp pulse signal. Each of these separated signals has a different center time. Through each chirp pulse signal in Doppler domain, the proposed method generates each frame of video at a high frame rate. The proposed ViSAR processing can show high efficiency with low computation and without a fixed coordinate system. Moreover, it can also visualize a wider area on stripmap mode than the conventional ViSAR mode, and can derive the video results based on Range Doppler Algorithm (RDA). These advantages can lead to reduce economic costs and simplify the operating ViSAR system. We have performed the practical experiments using X-band chirp pulse SAR system mounted on an airplane to verify the proposed method.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The signal processing technologies of synthetic aperture radar (SAR) have been vastly studied as diverse measurement modes for various applications. One of the technologies is Video-SAR (ViSAR). It is a land-imaging mode where a sequence of images is continuously formed on the spotlight mode. We propose a new signal processing method to generate the multi-frames of ViSAR using Doppler shifting technique via sub-aperture processing. The method is based on our designed wide-angle antenna, which is a corrugated horn shape with low side lobe and Gaussian beam pattern. This wide-angle antenna receives a wide Doppler band along the azimuth direction. Based on the characteristics of the antenna, we separate the wide Doppler band into each chirp pulse signal. Each of these separated signals has a different center time. Through each chirp pulse signal in Doppler domain, the proposed method generates each frame of video at a high frame rate. The proposed ViSAR processing can show high efficiency with low computation and without a fixed coordinate system. Moreover, it can also visualize a wider area on stripmap mode than the conventional ViSAR mode, and can derive the video results based on Range Doppler Algorithm (RDA). These advantages can lead to reduce economic costs and simplify the operating ViSAR system. We have performed the practical experiments using X-band chirp pulse SAR system mounted on an airplane to verify the proposed method. |
| 170. | Laxmikant Minz; Hyunseong Kang; Seong-Ook Park Low Reflection Coefficient Ku-Band Antenna Array for FMCW Radar Application Journal Article Progress In Electromagnetics Research, 102 , pp. 127-137, 2020. @article{Minz2020b, title = {Low Reflection Coefficient Ku-Band Antenna Array for FMCW Radar Application}, author = {Laxmikant Minz and Hyunseong Kang and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2021/03/09.20020302.pdf}, doi = {10.2528/PIERC20020302}, year = {2020}, date = {2020-05-25}, journal = {Progress In Electromagnetics Research}, volume = {102}, pages = {127-137}, abstract = {A radar for decisive target detection and tracking requires wideband, high return loss and high efficiency antenna array. In this paper, a 16 element staked-patch microstrip antenna array is presented at Ku-band with very low reflection coefficient for radar system. An aperture coupled feeding approach for a stack patch antenna is employed for wide bandwidth. A thin and low-loss tangent material, Taconic TLY-5, is used in the design of an antenna array to minimize the surface current loss and dielectric loss. Moreover, the antenna is designed with good impedance match, -30 dB, for high efficiency, by optimizing the stacked patches and utilizing reactive loading from u-slit on patch. For a low reflection coefficient antenna array over a wide bandwidth, an adequate feeding network consists of a compact and meandering stripline with metal-post around it is developed. The stripline configuration with metal-post minimizes crosstalk and lateral leakage. The feeding network developed has low reflection coefficient of -30 dB for the target band. The simulated feeding network loss is also low, 0.5 dB. The overall size of the 16 element array is compact, 295 mm x 30 mm (14λ x 1.425λ). The antenna array performance gives a reflection coefficient of -30 dB in the range of 14-14.5 GHz and total efficiency of 80%. The gain of the array is 21.54 dBi at 14.25 GHz.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A radar for decisive target detection and tracking requires wideband, high return loss and high efficiency antenna array. In this paper, a 16 element staked-patch microstrip antenna array is presented at Ku-band with very low reflection coefficient for radar system. An aperture coupled feeding approach for a stack patch antenna is employed for wide bandwidth. A thin and low-loss tangent material, Taconic TLY-5, is used in the design of an antenna array to minimize the surface current loss and dielectric loss. Moreover, the antenna is designed with good impedance match, -30 dB, for high efficiency, by optimizing the stacked patches and utilizing reactive loading from u-slit on patch. For a low reflection coefficient antenna array over a wide bandwidth, an adequate feeding network consists of a compact and meandering stripline with metal-post around it is developed. The stripline configuration with metal-post minimizes crosstalk and lateral leakage. The feeding network developed has low reflection coefficient of -30 dB for the target band. The simulated feeding network loss is also low, 0.5 dB. The overall size of the 16 element array is compact, 295 mm x 30 mm (14λ x 1.425λ). The antenna array performance gives a reflection coefficient of -30 dB in the range of 14-14.5 GHz and total efficiency of 80%. The gain of the array is 21.54 dBi at 14.25 GHz. |
| 169. | Laxmikant Minz; Seong-Ook Park Beam scanning annular slot‐ring antenna array with via‐fence for wireless power transfer Journal Article International Journal of RF and Microwave Computer-Aided Engineering, 30 (6), 2020. @article{Minz2020, title = {Beam scanning annular slot‐ring antenna array with via‐fence for wireless power transfer}, author = {Laxmikant Minz and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2020/09/Beam-scanning-annular-slot‐ring-antenna-array-with-via‐fence-for-wireless-power-transfer.pdf}, doi = {doi.org/10.1002/mmce.22178}, year = {2020}, date = {2020-02-17}, journal = {International Journal of RF and Microwave Computer-Aided Engineering}, volume = {30}, number = {6}, abstract = {Wireless power transfer has been the field of research for many decades, and with technological advancement and increase in wireless mobile devices, the future of wireless power transfer technology is very promising. The major requirement of wireless power transfer is an efficient and compact antenna array with high gain and flawless scanning performance. In this article, a 4 × 8 element array is proposed with a gain of 18 dB and scanning capability of ±45° in azimuth and elevation plane at 5.8 GHz. The overall size of the array is 100 mm × 200 mm. The element separation in the array is only 0.48 λ. There was strong mutual coupling due to smaller separation, which has been minimized with the application of via‐fence around the antenna element. A dual feed circularly polarized annular slot‐ring antenna is proposed and analyzed with via‐fence to develop an array of 4 × 8 elements. The antenna array reflection coefficient obtained is less than 20 dB for different scan angles and the gain of the array obtained is also within 2 dB for ±45° scan angles.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Wireless power transfer has been the field of research for many decades, and with technological advancement and increase in wireless mobile devices, the future of wireless power transfer technology is very promising. The major requirement of wireless power transfer is an efficient and compact antenna array with high gain and flawless scanning performance. In this article, a 4 × 8 element array is proposed with a gain of 18 dB and scanning capability of ±45° in azimuth and elevation plane at 5.8 GHz. The overall size of the array is 100 mm × 200 mm. The element separation in the array is only 0.48 λ. There was strong mutual coupling due to smaller separation, which has been minimized with the application of via‐fence around the antenna element. A dual feed circularly polarized annular slot‐ring antenna is proposed and analyzed with via‐fence to develop an array of 4 × 8 elements. The antenna array reflection coefficient obtained is less than 20 dB for different scan angles and the gain of the array obtained is also within 2 dB for ±45° scan angles. |
| 168. | Chul-Ki Kim; Laxmikant Minz; Seong-Ook Park Improved Measurement Method of Material Properties Using Continuous Cavity Perturbation Without Relocation Journal Article IEEE Transactions on Instrumentation and Measurement, 69 (8), pp. 5702 - 5716, 2020. @article{Kim2020d, title = {Improved Measurement Method of Material Properties Using Continuous Cavity Perturbation Without Relocation}, author = {Chul-Ki Kim and Laxmikant Minz and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2020/09/Improved-Measurement-Method-of-Material-Properties-Using-Continuous-Cavity-Perturbation-Without-Relocation.pdf}, doi = {10.1109/TIM.2020.2966358}, year = {2020}, date = {2020-01-14}, journal = {IEEE Transactions on Instrumentation and Measurement}, volume = {69}, number = {8}, pages = {5702 - 5716}, abstract = {Depolarized fields inside a magnetodielectric sample interfere with the accurate measurement of sample characteristics in a cavity perturbation method. These depolarized fields occur due to the polarization of the test sample, depending on the volume and shape of the sample, in the electromagnetic field. To characterize the magnetodielectric sample more accurately, we proposed an advanced rectangular cavity (RC) perturbation method. In this method, we investigated the change in the resonant frequency and Q-factor of a cavity which depends on the volume, and shape of the sample, and depolarized fields within the sample. The depolarizing factor for calculating the permittivity and permeability of the sample is derived by separating the uniform and depolarized fields within the sample when the sample is inserted in the cavity. These separations of fields play an important role to improve the measurement accuracy. The proposed unified RC perturbation technique is validated initially by measuring the resonant frequency and quality factor and then calculating the complex permittivity and permeability at the TE 10l mode. The standard dielectric material (Al 2 O 3 ) and magnetic material (YIG) samples are measured with the vector network analyzer. The measurement was performed when the magnetodielectric sample having various shapes and volumes inserted into the RC resonator. In comparison with the previous cavity perturbation methods, the permittivity and permeability have been calculated more accurately with various shapes of the test sample, and we also found that the ratio of the maximum sample volume to the cavity for various samples increases about 40%. Based on the proposed method, for a cube-shaped sample, we obtained the complex permittivity and permeability consecutively at each resonance mode without any physical relocation of the test sample. Therefore, the test sample is capable of continuous more accurate and more effective measurement in the desired frequency band without relocation using the proposed technique.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Depolarized fields inside a magnetodielectric sample interfere with the accurate measurement of sample characteristics in a cavity perturbation method. These depolarized fields occur due to the polarization of the test sample, depending on the volume and shape of the sample, in the electromagnetic field. To characterize the magnetodielectric sample more accurately, we proposed an advanced rectangular cavity (RC) perturbation method. In this method, we investigated the change in the resonant frequency and Q-factor of a cavity which depends on the volume, and shape of the sample, and depolarized fields within the sample. The depolarizing factor for calculating the permittivity and permeability of the sample is derived by separating the uniform and depolarized fields within the sample when the sample is inserted in the cavity. These separations of fields play an important role to improve the measurement accuracy. The proposed unified RC perturbation technique is validated initially by measuring the resonant frequency and quality factor and then calculating the complex permittivity and permeability at the TE 10l mode. The standard dielectric material (Al 2 O 3 ) and magnetic material (YIG) samples are measured with the vector network analyzer. The measurement was performed when the magnetodielectric sample having various shapes and volumes inserted into the RC resonator. In comparison with the previous cavity perturbation methods, the permittivity and permeability have been calculated more accurately with various shapes of the test sample, and we also found that the ratio of the maximum sample volume to the cavity for various samples increases about 40%. Based on the proposed method, for a cube-shaped sample, we obtained the complex permittivity and permeability consecutively at each resonance mode without any physical relocation of the test sample. Therefore, the test sample is capable of continuous more accurate and more effective measurement in the desired frequency band without relocation using the proposed technique. |
| 167. | Junhyeong Park; Dae-Hwan Jung; Kyung-Bin Bae; Seong-Ook Park Range-Doppler Map Improvement in FMCW Radar for Small Moving Drone Detection Using the Stationary Point Concentration Technique Journal Article IEEE Transactions on Microwave Theory and Techniques, 68 (5), pp. 1858 - 1871, 2020. @article{Park2020c, title = {Range-Doppler Map Improvement in FMCW Radar for Small Moving Drone Detection Using the Stationary Point Concentration Technique}, author = {Junhyeong Park and Dae-Hwan Jung and Kyung-Bin Bae and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2020/09/Range-Doppler-Map-Improvement-in-FMCW-Radar-for-Small-Moving-Drone-Detection-Using-the-Stationary-Point-Concentration-Technique.pdf}, doi = {10.1109/TMTT.2019.2961911}, year = {2020}, date = {2020-01-13}, journal = {IEEE Transactions on Microwave Theory and Techniques}, volume = {68}, number = {5}, pages = {1858 - 1871}, abstract = {Given the rapidly growing drone market, the development of drone detection radars has become highly important to prevent drones from damaging lives and property. Frequency-modulated continuous-wave (FMCW) radars have been frequently used for drone detection. Among the architectures of FMCW radar, a heterodyne architecture that involves different local oscillators and produces beat signals at the IF stage has often been chosen. The FMCW radar, however, has a chronic problem called leakage. In an earlier study, we proposed the stationary point concentration (SPC) technique to improve the signal-to-noise ratio (SNR) of small drones by reducing the increase in noise floor caused by leakage. We demonstrated that the proposed technique increases the SNR of small hovering drones in the 1-D power spectrum. In this article, we newly analyze the practical problems in the heterodyne FMCW radar system. One is the 2-D noise floor increase in the range-Doppler (r-D) map due to the leakage, and the other is unwanted Doppler shifts. Then, we propose an upgraded theory and realization method of the SPC technique for the detection of the small moving drone by improving the r-D map. We prove that the proposed method not only reduces the 2-D noise floor by mitigating the leakage but also removes the unwanted Doppler shifts by the phase calibration. Consequently, we show that the proposed method increases the SNR of the small moving drone and corrects its velocity information at the same time in the r-D map.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Given the rapidly growing drone market, the development of drone detection radars has become highly important to prevent drones from damaging lives and property. Frequency-modulated continuous-wave (FMCW) radars have been frequently used for drone detection. Among the architectures of FMCW radar, a heterodyne architecture that involves different local oscillators and produces beat signals at the IF stage has often been chosen. The FMCW radar, however, has a chronic problem called leakage. In an earlier study, we proposed the stationary point concentration (SPC) technique to improve the signal-to-noise ratio (SNR) of small drones by reducing the increase in noise floor caused by leakage. We demonstrated that the proposed technique increases the SNR of small hovering drones in the 1-D power spectrum. In this article, we newly analyze the practical problems in the heterodyne FMCW radar system. One is the 2-D noise floor increase in the range-Doppler (r-D) map due to the leakage, and the other is unwanted Doppler shifts. Then, we propose an upgraded theory and realization method of the SPC technique for the detection of the small moving drone by improving the r-D map. We prove that the proposed method not only reduces the 2-D noise floor by mitigating the leakage but also removes the unwanted Doppler shifts by the phase calibration. Consequently, we show that the proposed method increases the SNR of the small moving drone and corrects its velocity information at the same time in the r-D map. |
2019 |
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| 166. | Chan-Yong Jung; Kyung-Bin Bae; Dong-Chan Kim; Seong-Ook Park Internal Calibration System Using Learning Algorithm With Gradient Descent Journal Article IEEE Geoscience and Remote Sensing Letters, 17 (9), pp. 1503 - 1507, 2019. @article{Jung2019d, title = {Internal Calibration System Using Learning Algorithm With Gradient Descent}, author = {Chan-Yong Jung and Kyung-Bin Bae and Dong-Chan Kim and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2020/09/Internal-Calibration-System-Using-Learning-Algorithm-With-Gradient-Descent.pdf}, doi = {10.1109/LGRS.2019.2950671}, year = {2019}, date = {2019-11-14}, journal = {IEEE Geoscience and Remote Sensing Letters}, volume = {17}, number = {9}, pages = {1503 - 1507}, abstract = {We present a novel approach to internal calibration of a radar system. A Ku-band radar system with internal calibration paths is designed. Thermal drift of a system is mainly caused by active components, which are a high-power amplifier (HPA) and a low-noise amplifier (LNA). We aimed to reduce the drift using a learning algorithm with a gradient-descent method. Hardware offset factors and calibration factors are introduced for the process. In the learning algorithm, a penalty term is formed based on the analysis of local minimum points. The result verifies the proposed internal calibration method. Maximum deviations of gain are 0.0477 dB for the HPA and 0.0132 dB for the LNA. In addition, the maximum deviations of phase are 0.2481° for HPA and 0.0722° for LNA, respectively.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a novel approach to internal calibration of a radar system. A Ku-band radar system with internal calibration paths is designed. Thermal drift of a system is mainly caused by active components, which are a high-power amplifier (HPA) and a low-noise amplifier (LNA). We aimed to reduce the drift using a learning algorithm with a gradient-descent method. Hardware offset factors and calibration factors are introduced for the process. In the learning algorithm, a penalty term is formed based on the analysis of local minimum points. The result verifies the proposed internal calibration method. Maximum deviations of gain are 0.0477 dB for the HPA and 0.0132 dB for the LNA. In addition, the maximum deviations of phase are 0.2481° for HPA and 0.0722° for LNA, respectively. |
| 165. | Dae-Hwan Jung; Hyun-Seong Kang; Chul-Ki Kim; Junhyeong Park; Seong-Ook Park Sparse Scene Recovery for High-Resolution Automobile FMCW SAR via Scaled Compressed Sensing Journal Article IEEE Transactions on Geoscience and Remote Sensing, 57 (12), pp. 10136 - 10146, 2019. @article{Jung2019c, title = {Sparse Scene Recovery for High-Resolution Automobile FMCW SAR via Scaled Compressed Sensing}, author = {Dae-Hwan Jung and Hyun-Seong Kang and Chul-Ki Kim and Junhyeong Park and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2020/02/08805113-2.pdf}, doi = {10.1109/TGRS.2019.2931626}, year = {2019}, date = {2019-08-19}, journal = {IEEE Transactions on Geoscience and Remote Sensing}, volume = {57}, number = {12}, pages = {10136 - 10146}, abstract = {This paper introduces a sparse scene reconstruction algorithm for automobile frequency-modulated continuous-wave synthetic aperture radar (FMCW SAR) through scaled compressed sensing (CS). An FMCW radar leads to low manufacturing cost, compact realization, and low transmission power. An automobile SAR is more economical and easier to implement than typical SAR platforms (e.g., satellites and aircraft). We apply CS to randomly subsampled raw data of automobile FMCW SAR for sparse reconstruction. We exploit the fact that the velocity of an automobile is significantly lower than that of the SAR platforms, which leads to a vastly narrow bandwidth of an azimuth-matched filter in the azimuth compression of the range-Doppler algorithm (RDA). Low-frequency azimuth data have a fundamental effect on azimuth compression. We propose a new reconstruction scheme, scaled CS, which specializes in low-frequency information recovery for automobile SAR. The scheme is based on basis pursuit denoising (BPDN). A Ku-band FMCW SAR system is developed to verify the performance of the proposed algorithm. We mount our system on an automobile and collect FMCW SAR raw data in the stripmap mode with a van maintained a constant speed on a highway. The proposed reconstruction algorithm shows improved recovery performance for automobile FMCW SAR, which is validated by processing a high-resolution real SAR image.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper introduces a sparse scene reconstruction algorithm for automobile frequency-modulated continuous-wave synthetic aperture radar (FMCW SAR) through scaled compressed sensing (CS). An FMCW radar leads to low manufacturing cost, compact realization, and low transmission power. An automobile SAR is more economical and easier to implement than typical SAR platforms (e.g., satellites and aircraft). We apply CS to randomly subsampled raw data of automobile FMCW SAR for sparse reconstruction. We exploit the fact that the velocity of an automobile is significantly lower than that of the SAR platforms, which leads to a vastly narrow bandwidth of an azimuth-matched filter in the azimuth compression of the range-Doppler algorithm (RDA). Low-frequency azimuth data have a fundamental effect on azimuth compression. We propose a new reconstruction scheme, scaled CS, which specializes in low-frequency information recovery for automobile SAR. The scheme is based on basis pursuit denoising (BPDN). A Ku-band FMCW SAR system is developed to verify the performance of the proposed algorithm. We mount our system on an automobile and collect FMCW SAR raw data in the stripmap mode with a van maintained a constant speed on a highway. The proposed reconstruction algorithm shows improved recovery performance for automobile FMCW SAR, which is validated by processing a high-resolution real SAR image. |
| 164. | Chul-Ki Kim; Jung-Su Lee; Jang-Soo Chae; Seong-Ook Park A Modified Stripmap SAR Processing for Vector Velocity Compensation Using the Cross-Correlation Estimation Method Journal Article Journal of Electromagnetic Engineering and Science, 19 (3), pp. 159-165, 2019. @article{Kim2019c, title = {A Modified Stripmap SAR Processing for Vector Velocity Compensation Using the Cross-Correlation Estimation Method}, author = {Chul-Ki Kim and Jung-Su Lee and Jang-Soo Chae and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2020/03/jees-2019-19-3-159.pdf}, doi = {doi.org/10.26866/jees.2019.19.3.159}, year = {2019}, date = {2019-07-31}, journal = {Journal of Electromagnetic Engineering and Science}, volume = {19}, number = {3}, pages = {159-165}, abstract = {This paper proposes a modified stripmap synthetic aperture radar (SAR) signal processing algorithm with an X-band SAR system, using the practical measurement results of automobile-based SAR (Auto-SAR). The quality of the image is degraded due to an unexpected direction change or anisotropy of the target position in radar image measurement. To solve the quality problem, signal processing is required for the vector velocity of each range in the azimuth direction. An X-band chirp pulse system was implemented and optimized by a signal processing algorithm suitable for high resolution. The stripmap SAR images are produced in five places. The validity of the proposed algorithm is verified by comparing impulse response function analysis and experimental images.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper proposes a modified stripmap synthetic aperture radar (SAR) signal processing algorithm with an X-band SAR system, using the practical measurement results of automobile-based SAR (Auto-SAR). The quality of the image is degraded due to an unexpected direction change or anisotropy of the target position in radar image measurement. To solve the quality problem, signal processing is required for the vector velocity of each range in the azimuth direction. An X-band chirp pulse system was implemented and optimized by a signal processing algorithm suitable for high resolution. The stripmap SAR images are produced in five places. The validity of the proposed algorithm is verified by comparing impulse response function analysis and experimental images. |
| 163. | Tae-Wan Kim; Seong-Ook Park Enhanced gain and miniaturisation method of stacked dielectric resonator antenna using metallic cap Journal Article IET Microwaves, Antennas & Propagation, 13 (8), pp. 1198 - 1201, 2019. @article{Kim2019b, title = {Enhanced gain and miniaturisation method of stacked dielectric resonator antenna using metallic cap}, author = {Tae-Wan Kim and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2020/02/08744166.pdf}, doi = {10.1049/iet-map.2018.5606}, year = {2019}, date = {2019-06-24}, journal = {IET Microwaves, Antennas & Propagation}, volume = {13}, number = {8}, pages = {1198 - 1201}, abstract = {The authors introduce a miniature and gain enhancement method of dielectric resonator antenna (DRA) using a metallic cap. The structure of the proposed antenna consists of a stacked cylindrical dielectric resonator, a metallic cap that is located on the resonator, and a ground plane. By adjusting the size of the metallic cap while retaining the size of the antenna, the proposed antenna operates in the lower frequency band and shows improved realised gain. As the radius of metallic cap increases, wavelength at z -axis increases and the resonance frequency gets lower. In addition, tangential field at side wall surface increases, which leads to the enhancement of realised gain at resonance frequency. The authors have fabricated a prototype of the antenna for the experimental verification. The simulation results are in a close agreement with the experimental finding.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The authors introduce a miniature and gain enhancement method of dielectric resonator antenna (DRA) using a metallic cap. The structure of the proposed antenna consists of a stacked cylindrical dielectric resonator, a metallic cap that is located on the resonator, and a ground plane. By adjusting the size of the metallic cap while retaining the size of the antenna, the proposed antenna operates in the lower frequency band and shows improved realised gain. As the radius of metallic cap increases, wavelength at z -axis increases and the resonance frequency gets lower. In addition, tangential field at side wall surface increases, which leads to the enhancement of realised gain at resonance frequency. The authors have fabricated a prototype of the antenna for the experimental verification. The simulation results are in a close agreement with the experimental finding. |
| 162. | Rao Shahid Aziz; Tae-Wan Kim; Jae-Seok Park; Young-Ho Ryu; Seong-Ook Park EM lens design using thin planar metasurfaces for high antenna gain and low SLL applications Journal Article IET Microwaves, Antennas & Propagation, 13 (7), pp. 950- - 958, 2019. @article{Aziz2019, title = {EM lens design using thin planar metasurfaces for high antenna gain and low SLL applications}, author = {Rao Shahid Aziz and Tae-Wan Kim and Jae-Seok Park and Young-Ho Ryu and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2020/02/EM-lens-design-using-thin-planar-metasurfaces-for-high-antenna-gain-and-low-SLL-applications-2.pdf}, doi = {10.1049/iet-map.2018.5671}, year = {2019}, date = {2019-06-20}, journal = {IET Microwaves, Antennas & Propagation}, volume = {13}, number = {7}, pages = {950- - 958}, abstract = {A novel electromagnetic (EM) lens with high gain, suppressed side-lobe level (SLL) and low profile is designed using thin planar metasurfaces. The proposed design consists of a source patch antenna and an EM lens based on two thin planar metasurfaces. The two thin metasurfaces with an air gap are placed at the focal distance H of about λ /2.25 above the source patch antenna. This configuration forms a thin planar lens in which the source patch antenna emitted quasi-spherical wave in order to transform into plane wave. The total size of source antenna and an EM lens is same. The miniaturised EM lens antenna faces high SLL, which can be reduced by maintaining the uniform transmission phase coefficient and tunable transmission amplitude coefficient of metasurface unit cells. By implementing this topology on metasurfaces, the SLL of the proposed EM lens can be reduced without affecting the boresight gain of source patch antenna. The measured results of the proposed EM lens achieve 7 dB gain enhancement at designed frequency (5.8 GHz) with the SLL suppression of -24 dB. The total volume of planar lens antenna is 1.17 λ × 1.17 λ × λ /2.25 mm 3 , which is very compact compared with other reported planar lens designs.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A novel electromagnetic (EM) lens with high gain, suppressed side-lobe level (SLL) and low profile is designed using thin planar metasurfaces. The proposed design consists of a source patch antenna and an EM lens based on two thin planar metasurfaces. The two thin metasurfaces with an air gap are placed at the focal distance H of about λ /2.25 above the source patch antenna. This configuration forms a thin planar lens in which the source patch antenna emitted quasi-spherical wave in order to transform into plane wave. The total size of source antenna and an EM lens is same. The miniaturised EM lens antenna faces high SLL, which can be reduced by maintaining the uniform transmission phase coefficient and tunable transmission amplitude coefficient of metasurface unit cells. By implementing this topology on metasurfaces, the SLL of the proposed EM lens can be reduced without affecting the boresight gain of source patch antenna. The measured results of the proposed EM lens achieve 7 dB gain enhancement at designed frequency (5.8 GHz) with the SLL suppression of -24 dB. The total volume of planar lens antenna is 1.17 λ × 1.17 λ × λ /2.25 mm 3 , which is very compact compared with other reported planar lens designs. |
| 161. | Muhammad Tayyab Azim; Junhyeong Park; Seong-Ook Park Contactless Linear Rotary Joint at Ku-Band Journal Article IEEE Antennas and Wireless Propagation Letters, 29 (6), pp. 373 - 375, 2019. @article{Azim2019, title = {Contactless Linear Rotary Joint at Ku-Band}, author = {Muhammad Tayyab Azim and Junhyeong Park and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2019/06/08708983.pdf}, doi = {10.1109/LMWC.2019.2912271}, year = {2019}, date = {2019-05-07}, journal = {IEEE Antennas and Wireless Propagation Letters}, volume = {29}, number = {6}, pages = {373 - 375}, abstract = {Our laboratory has developed a drone detection radar that involves a mechanical scanning antenna. Radar and antenna systems that have mechanical scanning require an additional component called a rotary joint (RJ). The purpose of RJ in scanning assemblies is to provide an uninterrupted link between the antenna and the transceiver. In our system, antenna and transceiver are linearly polarized and use TE 10 mode along the rectangular waveguide section. TE 10 modes are asymmetric in nature making them incompatible with the rotating motion of the antenna. An RJ is presented with back-to-back mode transitions using symmetric modes along the circular waveguide and contactless branch line joint. The mode used along the circular waveguide for symmetry purpose is TM 01 . An I-type linear RJ topology is selected due to lack of space along the lateral directions and system configuration. The problem of antenna matching while scanning was solved at 14.0–14.5 GHz at Ku -band using single-channel linear RJ.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Our laboratory has developed a drone detection radar that involves a mechanical scanning antenna. Radar and antenna systems that have mechanical scanning require an additional component called a rotary joint (RJ). The purpose of RJ in scanning assemblies is to provide an uninterrupted link between the antenna and the transceiver. In our system, antenna and transceiver are linearly polarized and use TE 10 mode along the rectangular waveguide section. TE 10 modes are asymmetric in nature making them incompatible with the rotating motion of the antenna. An RJ is presented with back-to-back mode transitions using symmetric modes along the circular waveguide and contactless branch line joint. The mode used along the circular waveguide for symmetry purpose is TM 01 . An I-type linear RJ topology is selected due to lack of space along the lateral directions and system configuration. The problem of antenna matching while scanning was solved at 14.0–14.5 GHz at Ku -band using single-channel linear RJ. |
| 160. | Woncheol Lee; Yang-Ki Hong; Hoyun Won; Minyeong Choi; Katelyn Isbell; Jaejin Lee; Tae-Wan Kim; Seong-Ook Park Lossy Ferrite Core-Dielectric Shell Structure for Miniature GHz Axial-Mode Helical Antenna Journal Article IEEE Antennas and Wireless Propagation Letters, 18 (5), pp. 951 - 955, 2019. @article{Lee2018b, title = {Lossy Ferrite Core-Dielectric Shell Structure for Miniature GHz Axial-Mode Helical Antenna}, author = {Woncheol Lee and Yang-Ki Hong and Hoyun Won and Minyeong Choi and Katelyn Isbell and Jaejin Lee and Tae-Wan Kim and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2019/06/08675390-1.pdf}, doi = {10.1109/LAWP.2019.2906505}, year = {2019}, date = {2019-03-27}, journal = {IEEE Antennas and Wireless Propagation Letters}, volume = {18}, number = {5}, pages = {951 - 955}, abstract = {A lossy ferrite core/dielectric shell structure effectively miniaturizes an axial-mode helical antenna (AM-HA) without sacrificing the antenna gain in the range of 2.85-3.45 GHz. Co 2 Z hexaferrite-glass composite was used as an inner core and acrylonitrile butadiene styrene as an outer shell. The volume of the AM-HA was reduced by 29% while maintaining realized gain of 9.0 dBic, compared to air-core AM-HA. The simulation also confirmed that further miniaturization of the AM-HA up to 43% is achievable with a slight decrease in realized gain from 9 to 8.7 dBic. The designed magnetic core/dielectric shell structure offers a vast selection of lossy ferrite for miniaturization of the AM-HA.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A lossy ferrite core/dielectric shell structure effectively miniaturizes an axial-mode helical antenna (AM-HA) without sacrificing the antenna gain in the range of 2.85-3.45 GHz. Co 2 Z hexaferrite-glass composite was used as an inner core and acrylonitrile butadiene styrene as an outer shell. The volume of the AM-HA was reduced by 29% while maintaining realized gain of 9.0 dBic, compared to air-core AM-HA. The simulation also confirmed that further miniaturization of the AM-HA up to 43% is achievable with a slight decrease in realized gain from 9 to 8.7 dBic. The designed magnetic core/dielectric shell structure offers a vast selection of lossy ferrite for miniaturization of the AM-HA. |
| 159. | Dong-Chan Kim; Seong-Jin Park; Tae-Wan Kim; Laxmikant Minz; Seong-Ook Park Fully Digital Beamforming Receiver With a Real-Time Calibration for 5G Mobile Communication Journal Article IEEE Transactions on Antennas and Propagation, 67 (6), pp. 3809 - 3819, 2019. @article{Kim2017n, title = {Fully Digital Beamforming Receiver With a Real-Time Calibration for 5G Mobile Communication}, author = {Dong-Chan Kim and Seong-Jin Park and Tae-Wan Kim and Laxmikant Minz and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2019/06/08657999_1.pdf}, doi = {10.1109/TAP.2019.2902712}, year = {2019}, date = {2019-03-04}, journal = {IEEE Transactions on Antennas and Propagation}, volume = {67}, number = {6}, pages = {3809 - 3819}, abstract = {This paper presents a fully digital beamforming receiver (FDBR) using a method that calibrates the signals of all chains in real time, and is targeted for 5G mobile communication. In the real-time calibration method, the received signals of all chains are adjusted to correct the errors of phase and amplitude using the in-band signal other than operating frequency for calibration. The proposed FDBR with real-time calibration is designed and fabricated. The FDBR consists of eight chains of the tapered slot antenna (TSA) element, low noise block (LNB), and software defined radios (SDRs). The 1 × 8 array TSA with the directional coupler and the 1:8 divider is designed to send eight uniform calibration signals along with the received signal of all the chains. In SDR, the digital phase shifter and the real-time calibration blocks are implemented to realize digital beamforming. The digital phase shifter has an extremely high resolution of 0.72°. After using the real-time calibration method, the average of measured phase and amplitude error between each chain is less than 0.9° and 0.5 dB, respectively. To verify the beamforming performance of the FDBR, the simulation radiation pattern and the measurement radiation pattern are compared for 0°, ±15°, ±30°, and ±45° beam angles. The simulation results are in good agreement with the measured results. An excellent beamforming performance is achieved in the 1 × 8 array FDBR using the real-time calibration.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper presents a fully digital beamforming receiver (FDBR) using a method that calibrates the signals of all chains in real time, and is targeted for 5G mobile communication. In the real-time calibration method, the received signals of all chains are adjusted to correct the errors of phase and amplitude using the in-band signal other than operating frequency for calibration. The proposed FDBR with real-time calibration is designed and fabricated. The FDBR consists of eight chains of the tapered slot antenna (TSA) element, low noise block (LNB), and software defined radios (SDRs). The 1 × 8 array TSA with the directional coupler and the 1:8 divider is designed to send eight uniform calibration signals along with the received signal of all the chains. In SDR, the digital phase shifter and the real-time calibration blocks are implemented to realize digital beamforming. The digital phase shifter has an extremely high resolution of 0.72°. After using the real-time calibration method, the average of measured phase and amplitude error between each chain is less than 0.9° and 0.5 dB, respectively. To verify the beamforming performance of the FDBR, the simulation radiation pattern and the measurement radiation pattern are compared for 0°, ±15°, ±30°, and ±45° beam angles. The simulation results are in good agreement with the measured results. An excellent beamforming performance is achieved in the 1 × 8 array FDBR using the real-time calibration. |
| 158. | Junhyeong Park; Seungwoon Park; Do-Hoon Kim; Seong-Ook Park Leakage Mitigation in Heterodyne FMCW RADAR for Small Drone Detection With Stationary Point Concentration Technique Journal Article IEEE Transactions on Microwave Theory and Techniques, 67 (3), pp. 1221 - 1232, 2019. @article{Park2017eb, title = {Leakage Mitigation in Heterodyne FMCW RADAR for Small Drone Detection With Stationary Point Concentration Technique}, author = {Junhyeong Park and Seungwoon Park and Do-Hoon Kim and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2019/06/Leakage-Mitigation-in-Heterodyne-FMCW-RADAR-for-Small-Drone-Detection-With-Stationary-Point-Concentration-Technique.pdf}, doi = {10.1109/TMTT.2018.2889045}, year = {2019}, date = {2019-01-08}, journal = {IEEE Transactions on Microwave Theory and Techniques}, volume = {67}, number = {3}, pages = {1221 - 1232}, abstract = {To prevent potential hazards posed by fast-evolving drones, it is of importance to develop a radar system for drone detection. Frequency modulated continuous wave (FMCW) radars are widely used for that purpose. Heterodyne architectures are preferred for them to mitigate dc offset errors. Having said that, FMCW radars suffer from permanent leakage from the transmitter into the receiver. The leakage phase noise raises the total noise floor and limits the radar sensitivity. Here, we propose a stationary point concentration (SPC) technique in order to overcome the challenges. The SPC technique concentrates the leakage phase noise on a stationary point to alleviate the impact of the noise. The technique can be realized using digital signal processing without additional hardware. The results show that the proposed technique significantly lowers the noise floor.}, keywords = {}, pubstate = {published}, tppubtype = {article} } To prevent potential hazards posed by fast-evolving drones, it is of importance to develop a radar system for drone detection. Frequency modulated continuous wave (FMCW) radars are widely used for that purpose. Heterodyne architectures are preferred for them to mitigate dc offset errors. Having said that, FMCW radars suffer from permanent leakage from the transmitter into the receiver. The leakage phase noise raises the total noise floor and limits the radar sensitivity. Here, we propose a stationary point concentration (SPC) technique in order to overcome the challenges. The SPC technique concentrates the leakage phase noise on a stationary point to alleviate the impact of the noise. The technique can be realized using digital signal processing without additional hardware. The results show that the proposed technique significantly lowers the noise floor. |
2018 |
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| 157. | Dong-Uk Sim; Sang-Il Kwak; Jong-Hwa Kwon; Seong-Ook Park Microwave and Optical Technology Letters, 61 (3), pp. 801 - 804, 2018. @article{Sim2018b, title = {Design of new reverberation chamber for electromagnetic compatibility and wireless device measurement applications and its reproducibility performance validation}, author = {Dong-Uk Sim and Sang-Il Kwak and Jong-Hwa Kwon and Seong-Ook Park}, url = {http://ma.kaist.ac.kr/wp-content/uploads/2020/02/Sim_et_al-2019-Microwave_and_Optical_Technology_Letters.pdf}, doi = {http://dx.doi.org/10.1002/mop.31644}, year = {2018}, date = {2018-11-26}, journal = {Microwave and Optical Technology Letters}, volume = {61}, number = {3}, pages = {801 - 804}, abstract = {This article proposes new reverberation chamber structure for electromagnetic compatibility and wireless device measurement applications. It consists of dual plate type mode stirrers and two types of reflectors that improve its original field uniformity. Based on the SD and eigenmode analysis, their effect is demonstrated, and through the final measured results, it is shown that the proposed reverberation chamber has excellent SD characteristic of <2.5 dB at 650 MHz or higher. In addition, from the viewpoint of its utilization, it is verified that for over the air performance of a commercial long‐term evolution mobile phone, its experimental reproducibility is very high, and its results show little difference from those obtained in the anechoic chamber.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This article proposes new reverberation chamber structure for electromagnetic compatibility and wireless device measurement applications. It consists of dual plate type mode stirrers and two types of reflectors that improve its original field uniformity. Based on the SD and eigenmode analysis, their effect is demonstrated, and through the final measured results, it is shown that the proposed reverberation chamber has excellent SD characteristic of <2.5 dB at 650 MHz or higher. In addition, from the viewpoint of its utilization, it is verified that for over the air performance of a commercial long‐term evolution mobile phone, its experimental reproducibility is very high, and its results show little difference from those obtained in the anechoic chamber. |
| 156. | Tae-Wan Kim; Jun-Sung Park; Seong-Ook Park A Theoretical Model for Resonant Frequency and Radiation Pattern on Rectangular Microstrip Patch Antenna on Liquid Crystal Substrate Journal Article IEEE Transactions on Antennas and Propagation, 66 , pp. 4533-4540, 2018. @article{Kim2018b, title = {A Theoretical Model for Resonant Frequency and Radiation Pattern on Rectangular Microstrip Patch Antenna on Liquid Crystal Substrate}, author = {Tae-Wan Kim and Jun-Sung Park and Seong-Ook Park}, url = {http://143.248.148.42/wp-content/uploads/2018/10/08401523.pdf}, doi = {10.1109/TAP.2018.2851304}, year = {2018}, date = {2018-07-02}, journal = {IEEE Transactions on Antennas and Propagation}, volume = {66}, pages = {4533-4540}, abstract = {This paper presents a theoretical model of the rectangular-shaped microstrip patch antennas on liquid crystal (LC) substrates in order to accurately derive the resonant frequencies and radiation performances. The model is based on the solution of the mode matching about an LC loaded cavity. The calculation results of the theoretical model are compared with the experiment and simulation results. The discrepancy between calculation and simulation results is merely 2.7%. In addition, a tuning mechanism of the patch antenna on the LC substrate is verified depending on the strength of a biasing voltage. The calculated results of the theoretical model indicate that the resonant frequency is shifted toward lower direction and 3-dB beamwidth of radiation pattern increases as the bias voltage increases. Although the calculated maximum directivity decreases with the increment of voltage, the realized gain increases due to the radiation efficiency of the antenna.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper presents a theoretical model of the rectangular-shaped microstrip patch antennas on liquid crystal (LC) substrates in order to accurately derive the resonant frequencies and radiation performances. The model is based on the solution of the mode matching about an LC loaded cavity. The calculation results of the theoretical model are compared with the experiment and simulation results. The discrepancy between calculation and simulation results is merely 2.7%. In addition, a tuning mechanism of the patch antenna on the LC substrate is verified depending on the strength of a biasing voltage. The calculated results of the theoretical model indicate that the resonant frequency is shifted toward lower direction and 3-dB beamwidth of radiation pattern increases as the bias voltage increases. Although the calculated maximum directivity decreases with the increment of voltage, the realized gain increases due to the radiation efficiency of the antenna. |
| 155. | Tae-Wan Kim; Byeong-Yong Park; Woncheol Lee; Seong-Ook Park; Yang-Ki Hong Method for Computing Frequency Response and Radiation Pattern of Magnetized Cylindrical Ferrite Resonator Antenna Journal Article IEEE Transactions on Antennas and Propagation, 66 , pp. 4415 - 4425, 2018. @article{Kim2018c, title = {Method for Computing Frequency Response and Radiation Pattern of Magnetized Cylindrical Ferrite Resonator Antenna}, author = {Tae-Wan Kim and Byeong-Yong Park and Woncheol Lee and Seong-Ook Park and Yang-Ki Hong}, url = {http://143.248.148.42/wordpress/wp-content/uploads/2018/10/08401526.pdf}, doi = {10.1109/TAP.2018.2851359}, year = {2018}, date = {2018-07-02}, journal = {IEEE Transactions on Antennas and Propagation}, volume = {66}, pages = {4415 - 4425}, abstract = {This paper presents a theoretical model of a cylindrical ferrite resonator (FR) antenna that predicts resonance frequencies, the frequency tuning range, and radiation patterns. The FR antenna is placed on a PEC ground plane and is excited by a coaxial probe with a dc magnetic bias field applied in the direction transverse to the ground plane. An open-boundary model to predict the resonance frequency is introduced and compared with the measured results. The all-boundary model is in good agreement with the measured results compared with the other models. The discrepancy of the proposed model is less than 3%. The HE 11δ mode-splitting behavior caused by the tensor nature of the permeability of a biased ferrite is investigated. It is shown that the frequency and polarization of the antenna are tunable. The operating frequency can be chosen in the range from 8.54 to 10.115 GHz. In addition, the linear polarization is radiated at no bias, while the circular polarization is radiated at the magnetized case. The results of the theory correspond approximately with the measured and simulated results for radiation patterns.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper presents a theoretical model of a cylindrical ferrite resonator (FR) antenna that predicts resonance frequencies, the frequency tuning range, and radiation patterns. The FR antenna is placed on a PEC ground plane and is excited by a coaxial probe with a dc magnetic bias field applied in the direction transverse to the ground plane. An open-boundary model to predict the resonance frequency is introduced and compared with the measured results. The all-boundary model is in good agreement with the measured results compared with the other models. The discrepancy of the proposed model is less than 3%. The HE 11δ mode-splitting behavior caused by the tensor nature of the permeability of a biased ferrite is investigated. It is shown that the frequency and polarization of the antenna are tunable. The operating frequency can be chosen in the range from 8.54 to 10.115 GHz. In addition, the linear polarization is radiated at no bias, while the circular polarization is radiated at the magnetized case. The results of the theory correspond approximately with the measured and simulated results for radiation patterns. |
| 154. | Dong-Uk Sim; Sang-Il Kwak; Jong-Hwa Kwon; Seong-Ook Park Development and Validation of New Reverberation Chamber for Wireless Devices Journal Article Wireless Communications and Mobile Computing, pp. 12, 2018. @article{Sim2018, title = {Development and Validation of New Reverberation Chamber for Wireless Devices}, author = {Dong-Uk Sim and Sang-Il Kwak and Jong-Hwa Kwon and Seong-Ook Park}, url = {http://143.248.148.42/wordpress/wp-content/uploads/2018/10/7068601.pdf}, year = {2018}, date = {2018-06-26}, journal = {Wireless Communications and Mobile Computing}, pages = {12}, abstract = {This paper proposes a reverberation chamber structure consisting of new reflectors and mode stirrers for electromagnetic compatibility and wireless terminal measurements. The key design considerations for them are determined through a reasonable approach to analyze the eigenmode for a reverberation chamber and the standard deviation of its working volume based on 3D simulation. The final designs are expected to improve the standard deviation performance of the initial structure of the reverberation chamber and provide a better mode stirring environment. The results measured in the fabricated chamber demonstrate that these predictions are clearly realized. The results satisfy the main requirements of this paper, which are defined in consideration of the specifications of commercial reverberation chamber products. Therefore, the reverberation chamber of this paper is expected to be useful for performance measurement and evaluation of commercial wireless terminals. To verify this logical approach to obtain a good design and its results, the results measured in the actual fabricated reverberation chamber are described along with analytical and computational results.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper proposes a reverberation chamber structure consisting of new reflectors and mode stirrers for electromagnetic compatibility and wireless terminal measurements. The key design considerations for them are determined through a reasonable approach to analyze the eigenmode for a reverberation chamber and the standard deviation of its working volume based on 3D simulation. The final designs are expected to improve the standard deviation performance of the initial structure of the reverberation chamber and provide a better mode stirring environment. The results measured in the fabricated chamber demonstrate that these predictions are clearly realized. The results satisfy the main requirements of this paper, which are defined in consideration of the specifications of commercial reverberation chamber products. Therefore, the reverberation chamber of this paper is expected to be useful for performance measurement and evaluation of commercial wireless terminals. To verify this logical approach to obtain a good design and its results, the results measured in the actual fabricated reverberation chamber are described along with analytical and computational results. |
| 153. | Sungwoong Choi; Sangbong Jeon; Dongho Kim; Seong-Ook Park Method to reduce an unwanted EM field component in a 4-port TEM cell Journal Article Electronics Letters, 54 , pp. 488 - 490, 2018. @article{Choi2018, title = {Method to reduce an unwanted EM field component in a 4-port TEM cell}, author = {Sungwoong Choi and Sangbong Jeon and Dongho Kim and Seong-Ook Park}, url = {http://143.248.148.42/wordpress/wp-content/uploads/2018/10/08345093.pdf}, doi = {10.1049/el.2017.4831}, year = {2018}, date = {2018-04-30}, journal = {Electronics Letters}, volume = {54}, pages = {488 - 490}, abstract = {As an alternative standard electromagnetic (EM) field generator, a 4-port TEM (transverse EM) cell can be used for an EM compatibility (EMC) emission and immunity test. However, unwanted EM fields generated in a TEM cell deteriorate the results and accuracy of critical EMC tests. A new method to suppress unwanted field components in a 4-port TEM cell is proposed. To reduce the unwanted EM field, the narrow slits in internal septa are inserted, which are transverse with respect to the direction of wave propagation. By introducing the slits, the 4-port TEM cell can provide improved standard EM field distribution with the much-lowered unwanted field component inside the usable test volume.}, keywords = {}, pubstate = {published}, tppubtype = {article} } As an alternative standard electromagnetic (EM) field generator, a 4-port TEM (transverse EM) cell can be used for an EM compatibility (EMC) emission and immunity test. However, unwanted EM fields generated in a TEM cell deteriorate the results and accuracy of critical EMC tests. A new method to suppress unwanted field components in a 4-port TEM cell is proposed. To reduce the unwanted EM field, the narrow slits in internal septa are inserted, which are transverse with respect to the direction of wave propagation. By introducing the slits, the 4-port TEM cell can provide improved standard EM field distribution with the much-lowered unwanted field component inside the usable test volume. |
| 152. | Rao Shahid Aziz; Myung-Hun Jeong; Seong-Ook Park Low‐profile full‐metal‐rimmed antenna with less nonground portion for smartphones Journal Article Microwave and Optical Technology Letters, 60 , pp. 1187 - 1193, 2018. @article{Aziz2018, title = {Low‐profile full‐metal‐rimmed antenna with less nonground portion for smartphones}, author = {Rao Shahid Aziz and Myung-Hun Jeong and Seong-Ook Park}, url = {http://143.248.148.42/wordpress/wp-content/uploads/2018/10/rao1233s.pdf}, doi = {10.1002/mop.31121}, year = {2018}, date = {2018-04-08}, journal = {Microwave and Optical Technology Letters}, volume = {60}, pages = {1187 - 1193}, abstract = {In this article, a low‐profile full‐metal‐rimmed antenna with less nonground portion for smartphones is presented. The proposed antenna with full‐metal rim is designed on FR4 substrate within the volume of 115 × 60 × 5 mm3. Metal rim is made up of FR4 substrate with interconnected conducting vias which surrounds inner system circuit board. The gap between metal rim and system ground plane is 1.5 mm and they are connected by a single ground patch. Moreover, folded monopole branches are implemented on circuit board to obtain wide bandwidth and improve impedance matching at higher bands. Therefore, proposed antenna contains a system circuit board with monopole branches and a full metal rim which serves GSM (850), DCS (1800), PCS (1900), UMTS (2100), LTE (2300/2500), WiBro (2350), ISM (2400), SDM‐B (2650), and W‐LAN system operating bands. The proposed antenna also has an attractive feature of utilizing very less portion of ground clearance about 4 × 38 mm2 for placing monopole antenna and still covering a wide range of operating bands. This biggest merit makes it a potential candidate for metal rimmed smartphone applications with lesser nonground portion. A sample proposed structure has been realized on FR4 substrate to prove the design concept.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this article, a low‐profile full‐metal‐rimmed antenna with less nonground portion for smartphones is presented. The proposed antenna with full‐metal rim is designed on FR4 substrate within the volume of 115 × 60 × 5 mm3. Metal rim is made up of FR4 substrate with interconnected conducting vias which surrounds inner system circuit board. The gap between metal rim and system ground plane is 1.5 mm and they are connected by a single ground patch. Moreover, folded monopole branches are implemented on circuit board to obtain wide bandwidth and improve impedance matching at higher bands. Therefore, proposed antenna contains a system circuit board with monopole branches and a full metal rim which serves GSM (850), DCS (1800), PCS (1900), UMTS (2100), LTE (2300/2500), WiBro (2350), ISM (2400), SDM‐B (2650), and W‐LAN system operating bands. The proposed antenna also has an attractive feature of utilizing very less portion of ground clearance about 4 × 38 mm2 for placing monopole antenna and still covering a wide range of operating bands. This biggest merit makes it a potential candidate for metal rimmed smartphone applications with lesser nonground portion. A sample proposed structure has been realized on FR4 substrate to prove the design concept. |
| 151. | Woncheol Lee; Yang-Ki Hong; Minyeong Choi; Hoyun Won; Jaejin Lee; Seong-Ook Park; Seok Bae; Hwan-Sik Yoon Ferrite-Cored Patch Antenna With Suppressed Harmonic Radiation Journal Article IEEE Transactions on Antennas and Propagation, 66 , pp. 3154 - 3159, 2018. @article{Lee2018, title = {Ferrite-Cored Patch Antenna With Suppressed Harmonic Radiation}, author = {Woncheol Lee and Yang-Ki Hong and Minyeong Choi and Hoyun Won and Jaejin Lee and Seong-Ook Park and Seok Bae and Hwan-Sik Yoon}, url = {http://143.248.148.42/wordpress/wp-content/uploads/2018/10/08318672.pdf}, doi = {10.1109/TAP.2018.2816778}, year = {2018}, date = {2018-03-16}, journal = {IEEE Transactions on Antennas and Propagation}, volume = {66}, pages = {3154 - 3159}, abstract = {We designed and fabricated a multiple-ferrite-cored patch antenna (MFC-PA) to suppress harmonic radiation over the frequency range of 1-10 GHz and obtain wide suppressing bandwidth. Its suppression performance was compared to those of the conventional PA, photonic bandgap PA (PBG-PA), and defected ground structure PA (DGS-PA). Simulated and measured results show that MFC-PA effectively suppresses harmonic radiation up to 5.6 f0, where f0 is 0.9 GHz, while the harmonic radiation of PBG-PA and DGS-PA is suppressed up to 3 f0. It is suggested by the antenna performance simulation that MFC-PA can further suppress harmonic radiation up to 11 f0. In principle, the harmonic radiation of MFC-PA is suppressed by dissipating the unwanted signals in ferrite materials, whereas PBG-PA and DGS-PA suppress harmonic radiation by reflecting or redirecting unwanted signals, which is not desired. Ferrite loading is a unique approach to suppress any harmonic radiation.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We designed and fabricated a multiple-ferrite-cored patch antenna (MFC-PA) to suppress harmonic radiation over the frequency range of 1-10 GHz and obtain wide suppressing bandwidth. Its suppression performance was compared to those of the conventional PA, photonic bandgap PA (PBG-PA), and defected ground structure PA (DGS-PA). Simulated and measured results show that MFC-PA effectively suppresses harmonic radiation up to 5.6 f0, where f0 is 0.9 GHz, while the harmonic radiation of PBG-PA and DGS-PA is suppressed up to 3 f0. It is suggested by the antenna performance simulation that MFC-PA can further suppress harmonic radiation up to 11 f0. In principle, the harmonic radiation of MFC-PA is suppressed by dissipating the unwanted signals in ferrite materials, whereas PBG-PA and DGS-PA suppress harmonic radiation by reflecting or redirecting unwanted signals, which is not desired. Ferrite loading is a unique approach to suppress any harmonic radiation. |
| 150. | Tae-Wan Kim; Chan-Yong Jung; Seong-Ook Park Microwave Measurement of Initial Properties of Ferrites Using Mode Splitting Phenomenon by the Rod Resonator Method Journal Article Journal of Electromagnetic Waves and Applications, 32 , pp. 1306 - 1315, 2018. @article{Kim2018e, title = {Microwave Measurement of Initial Properties of Ferrites Using Mode Splitting Phenomenon by the Rod Resonator Method}, author = {Tae-Wan Kim and Chan-Yong Jung and Seong-Ook Park}, url = {http://143.248.148.42/wordpress/wp-content/uploads/2018/10/mmip.pdf}, doi = {10.1080/09205071.2018.1434017}, year = {2018}, date = {2018-02-02}, journal = {Journal of Electromagnetic Waves and Applications}, volume = {32}, pages = {1306 - 1315}, abstract = {This paper proposes an accurate method to calculate the permittivity and permeability of ferrites simultaneously at the demagnetized state. The eigenvalue equations for the resonator model can be obtained by applying the boundary condition of the structure of the resonator at both demagnetized and magnetized states. The complex permeability and permittivity are computed from the measured resonant frequencies and unloaded quality factors of the resonator using the mode splitting phenomenon. To verify the calculated magnetization values, the magneto-static simulation is performed by using CST EM studio based on the measured data of B–H curve. The measured complex permeability and permittivity of the demagnetized ferrite are verified by comparing with cavity perturbation method and statistic equation.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper proposes an accurate method to calculate the permittivity and permeability of ferrites simultaneously at the demagnetized state. The eigenvalue equations for the resonator model can be obtained by applying the boundary condition of the structure of the resonator at both demagnetized and magnetized states. The complex permeability and permittivity are computed from the measured resonant frequencies and unloaded quality factors of the resonator using the mode splitting phenomenon. To verify the calculated magnetization values, the magneto-static simulation is performed by using CST EM studio based on the measured data of B–H curve. The measured complex permeability and permittivity of the demagnetized ferrite are verified by comparing with cavity perturbation method and statistic equation. |
2017 |
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| 149. | Junhyeong Park; Jong-Wook Ham; Seungwoon Park; Do-Hoon Kim; Seong-Jin Park; Hyunseong Kang; Seong-Ook Park Polyphase-Basis Discrete Cosine Transform for Real-Time Measurement of Heart Rate With CW Doppler Radar Journal Article IEEE Transactions on Microwave Theory and Techniques, 66 , pp. 1644 - 1659, 2017. @article{Park2017e, title = {Polyphase-Basis Discrete Cosine Transform for Real-Time Measurement of Heart Rate With CW Doppler Radar}, author = {Junhyeong Park and Jong-Wook Ham and Seungwoon Park and Do-Hoon Kim and Seong-Jin Park and Hyunseong Kang and Seong-Ook Park}, url = {http://143.248.148.42/wordpress/wp-content/uploads/2018/10/08123523.pdf}, doi = {10.1109/TMTT.2017.2772782}, year = {2017}, date = {2017-11-28}, journal = {IEEE Transactions on Microwave Theory and Techniques}, volume = {66}, pages = {1644 - 1659}, abstract = {This paper presents a novel polyphase-basis discrete cosine transform that can be used for challenges to observe heart rate (HR) variability and sudden changes of HR in short time. To succeed in the challenges, real-time measurement which requires a short window length is needed. As the window length decreases, however, increased main-lobe width (MLW) and sidelobe width (SLW) result errors in measuring HR. Unlike commonly used discrete Fourier transform (DFT), the proposed method is based on DCT, which improves the accuracy of measured HR even though the short window length is used for the real-time measurement of HR. We demonstrate that the DCT can give 2 times shorter MLW and SLW than the DFT can. To verify the proposed method, it is compared with well-known existing methods, arctangent demodulation and complex signal demodulation, which use the DFT. We measured HR using a 10.225-GHz continuous-wave Doppler radar. In each experiment, the window lengths of 3, 2, and 1.5 s were used to measure HR in real time. Experimental results show that the proposed method has lower mean and standard deviation of errors than the existing methods have.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper presents a novel polyphase-basis discrete cosine transform that can be used for challenges to observe heart rate (HR) variability and sudden changes of HR in short time. To succeed in the challenges, real-time measurement which requires a short window length is needed. As the window length decreases, however, increased main-lobe width (MLW) and sidelobe width (SLW) result errors in measuring HR. Unlike commonly used discrete Fourier transform (DFT), the proposed method is based on DCT, which improves the accuracy of measured HR even though the short window length is used for the real-time measurement of HR. We demonstrate that the DCT can give 2 times shorter MLW and SLW than the DFT can. To verify the proposed method, it is compared with well-known existing methods, arctangent demodulation and complex signal demodulation, which use the DFT. We measured HR using a 10.225-GHz continuous-wave Doppler radar. In each experiment, the window lengths of 3, 2, and 1.5 s were used to measure HR in real time. Experimental results show that the proposed method has lower mean and standard deviation of errors than the existing methods have. |
| 148. | Dae-Hwan Jung; Seong-Ook Park Ku-band Car-borne FMCW Stripmap Synthetic Aperture Radar Journal Article International Symposium on Antenna and Propagation, 2017. @article{Jung2017, title = {Ku-band Car-borne FMCW Stripmap Synthetic Aperture Radar}, author = {Dae-Hwan Jung and Seong-Ook Park}, year = {2017}, date = {2017-10-31}, journal = {International Symposium on Antenna and Propagation}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
| 147. | Byung-Kwan Kim; Hyunseong Kang; Seong-Ook Park Experimental Analysis of Small Drone Polarimetry Based on Micro-Doppler Signature Journal Article IEEE Geoscience and Remote Sensing Letters, 14 , pp. 1670 - 1674, 2017. @article{Kim2017f, title = {Experimental Analysis of Small Drone Polarimetry Based on Micro-Doppler Signature}, author = {Byung-Kwan Kim and Hyunseong Kang and Seong-Ook Park}, url = {http://143.248.148.42/wordpress/wp-content/uploads/2018/10/08004431.pdf}, doi = {10.1109/LGRS.2017.2727824}, year = {2017}, date = {2017-08-09}, journal = {IEEE Geoscience and Remote Sensing Letters}, volume = {14}, pages = {1670 - 1674}, abstract = {We present a polarimetric analysis of small drones from different aspect angles. Polarimetric analysis can provide more information of a target, since the returned radar signal is affected by different wave polarization. The analysis is performed with micro-Doppler signature (MDS) to investigate micromotions of the drone detected by the radar. We measured operating small drones in an anechoic chamber from two aspect angles, 0° and 90°. An outdoor experiment was carried out with metal clutters for verification in real environment. The indoor analysis result shows that copolarized antenna receives signals better than cross polarized when the aspect angle is 0°, and vice versa. We also verified that cross-polarized antenna receives MDS from the drone better than copolarized antenna, from outdoors when an aspect angle is almost 90°. By utilizing the polarimetric characteristic of the drone at this frequency band, it is preferable to use a polarimetric radar for drone detection.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a polarimetric analysis of small drones from different aspect angles. Polarimetric analysis can provide more information of a target, since the returned radar signal is affected by different wave polarization. The analysis is performed with micro-Doppler signature (MDS) to investigate micromotions of the drone detected by the radar. We measured operating small drones in an anechoic chamber from two aspect angles, 0° and 90°. An outdoor experiment was carried out with metal clutters for verification in real environment. The indoor analysis result shows that copolarized antenna receives signals better than cross polarized when the aspect angle is 0°, and vice versa. We also verified that cross-polarized antenna receives MDS from the drone better than copolarized antenna, from outdoors when an aspect angle is almost 90°. By utilizing the polarimetric characteristic of the drone at this frequency band, it is preferable to use a polarimetric radar for drone detection. |
| 146. | Tae-Wan Kim; Rao Shahid Aziz; Seong-Ook Park Design of patch loaded with metallic posts inside dielectric resonator antenna Journal Article IET Microwaves, Antennas & Propagation, 11 , pp. 1483 - 1487, 2017. @article{Kim2017g, title = {Design of patch loaded with metallic posts inside dielectric resonator antenna}, author = {Tae-Wan Kim and Rao Shahid Aziz and Seong-Ook Park}, url = {http://143.248.148.42/wordpress/wp-content/uploads/2018/10/07999329.pdf}, doi = {10.1049/iet-map.2016.1026}, year = {2017}, date = {2017-08-03}, journal = {IET Microwaves, Antennas & Propagation}, volume = {11}, pages = {1483 - 1487}, abstract = {A new hybrid-antenna that is capable of wide-bandwidth operation and is small size is presented. The structure of the proposed antenna consists of a cylindrical dielectric resonator, metallic posts that are embedded in the resonator, and a rectangular patch. The proposed design generates three resonances: the full-cylindrical HE 11δ , half-HE 11δ -like mode, and radiation by the patch antenna. An electromagnetic analysis using a finite integration method (CST microwave studio) was performed to investigate the resonances. Furthermore, a prototype of antenna has fabricated for the experimental verification. The simulation results are in close agreement with the experimental findings. The proposed antenna offers a fractional bandwidth of 16.5% at the centre frequency of 9.27 GHz and a peak gain is >4.56 dBi in the matching band.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A new hybrid-antenna that is capable of wide-bandwidth operation and is small size is presented. The structure of the proposed antenna consists of a cylindrical dielectric resonator, metallic posts that are embedded in the resonator, and a rectangular patch. The proposed design generates three resonances: the full-cylindrical HE 11δ , half-HE 11δ -like mode, and radiation by the patch antenna. An electromagnetic analysis using a finite integration method (CST microwave studio) was performed to investigate the resonances. Furthermore, a prototype of antenna has fabricated for the experimental verification. The simulation results are in close agreement with the experimental findings. The proposed antenna offers a fractional bandwidth of 16.5% at the centre frequency of 9.27 GHz and a peak gain is >4.56 dBi in the matching band. |