THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE Aug.; 30(8),

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1 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE Aug.; 30(8), ISSN (Print)ISSN X (Online) Particle Swarm Optimization Study on Improved Performance of Polarimetric Calibration Using Particle Swarm Optimization 최인오 정성재 박상홍 신재민 양도철 김경태 In-Oh ChoiSeong-Jae Jung*Sang-Hong Park**Jae-Min Shin***Do-Chul Yang****Kyung-Tae Kim 요약 SAR(synthetic aperture radar).,,, SAR. PARC(polarimetric active radar calibrator)., PARC (channel imbalance: CI). PARC CI, 3 PARC 1, CI particle swarm optimization 2. SAR, SAR. Abstract With the development of state-of-the-art low earth orbit observation satellites, polarimetric synthetic aperture radar(sar) images have been widely utilized. However, polarimetric signals are inevitably distorted by channel imbalance(ci) and interference between multiple channels, resulting in rapidly degraded quality of polarimetric SAR images. Therefore, several polarimetric calibration methods using a polarimetric active radar calibrator(parc), which can provide different scattering matrices, have been developed. Nevertheless, errors generated by the performance of imperfect PARCs are inevitable, leading to significant errors of estimated CIs. In this study, we propose a framework for calibrating polarimetric SAR images, which consists of two stages: 1) coarse estimation of distortion parameters through a conventional method using three PARCs, and 2) fine estimation of CIs using particle swarm optimization and a single PARC. In simulations using polarimetric SAR images, we observed that our proposed method can more accurately calibrate polarimetric SAR images as compared to conventional methods. Key words: Polarimetric Calibration, Polarimetric Active Radar Calibrator, Synthetic Aperture Radar, Coner Reflector, Power Ratio (Department of Electrical Engineering, Pohang University of Science and Technology) * (Department of Network Business, Samsung) ** (Department of Electronic Engineering, Pukyong National University) *** (Satellite R&D Head Office, Korea Aerospace Research Institute) **** (Satellite Operation & Application Center, Korea Aerospace Research Institute) Manuscript received June 13, 2019 ; Revised August 27, 2019 ; Accepted August 27, (ID No ) Corresponding Author: Kyung-Tae Kim ( kkt@postech.ac.kr) c Copyright The Korean Institute of Electromagnetic Engineering and Science. All Rights Reserved. 649

2 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 30, no. 8, Aug 서론 (LEO Observation Satellite) SAR(Synthetic Aperture Radar)., SAR 1 [1]., (polarimetric calibration), (i.e. channel imbalance) HH(horizontal-to-horizontal), HV (horizontal- to-vertical), VH(vertical-to-horizontal) VV(vertical-to -vertical) (i.e. cross-talk), radiometric calibration. SAR [2][6].,, 12, (analytic method) [2],[3]. (distributed target) polarimetric active radar calibrator(parc) [4]., HV VH (i.e. reciprocity theorem [3] ) HH VV HV VH (i.e. azimuth symmetry [3] ),., 3 PARC [4],[5]., PARC., (numerical method) [6].,,. SAR, 그림 1. SAR [1] Fig. 1. Calibration procedure of satellite for SAR [1].., 3 PARC 1 PARC particle swarm optimization(pso) [7] 2 SAR., [4] PARC 2, PSO 2. SAR, SAR.. 신호모델링및문제점분석 2-1 다중편파신호모델링 4 HH, HV, VH VV. X 650

3 Particle Swarm Optimization (ionosphere) [3],. (1),,,,,,,,,., channel imbalance,,, cross-talk [3],[6].,,,, (1) 다중편파보정을위한기존방법들의문제점 12 [3],[6]. 1 PARC [3], 2. (2) if (3) *, i j H V. (2) (3) reciprocity theorem azimuth symmetry [3]. (1), i=1, 2,..., 4, j=1, 2,..., 4. (4),,,,,, i=1, 2,..., 3, j=1, 2,..., 3 (1) 3 3 (Ref. [3] )., (4). PARC 12 [3]. (2) (3). (5) 651

4 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 30, no. 8, Aug (a) HH SAR (a) SAR image for HH channel (b) HV SAR (b) SAR image for HV channel (c) VH SAR (c) SAR image for VH channel, 2 Radarsat-2 SAR HV VH SAR (i.e. (2) reciprocity theorem )., HH HV SAR = db (i.e. (3) azimuth symmetry )., Radarsat-2 SAR (4)., [3] (4)., (4), ( 3 ),. [6] (2) (3),. PARC [4] 3 PARC. (6) (d) VV SAR (d) SAR image for VV channel 그림 2. Radarsat-2 SAR Fig. 2. Polarimetric SAR images using Radarsat-2. 그림 3. Fig. 3. Average error between original covariance and approximated covariance. 652

5 Particle Swarm Optimization (7) (8) PARC [4],[5]. PARC (i.e. ), (6) (8) (1). (a) HH (b) HV (c) VH (d) VV 그림 4. (6) PARC SAR Fig. 4. Polarimetric SAR images for PARC of eq. (6).,, 3 PARC PARC [4]., (9) [3], PARC channel imbalance., 4 PARC SAR [4], 5 PARC., PARC (9) 그림 5. PARC Fig. 5. Estimation error of parameters for various errors of PARC., H V PARC. PARC.. 제안된기법 653

6 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 30, no. 8, Aug PARC 1, PARC particle swarm optimization (PSO) [7] 2 SAR. 1 3 PARC 2 PARC. (10) (10) (1),. PSO 2. cos cos (11) (12), (11) 0. 2 [7]. (13) particle 1 2, particle, particle,,.. 시뮬레이션결과 (6) (8) (10) PARC, 4 PARC SAR., PARC 30 db, (1) channel imbalance, channel imbalance, cross talk 30 db 10 db, cross talk 50 [1][3]. PSO 1. [3],[4] 2 SAR PARC SAR,. SNR(signal-to-noise ratio)=30, 25,..., 0 db. [3] [4] 표 1. PSO Table 1. Simulation parameters for PSO algorithm. Population 10,000 Iteration 10 Inertia weight 0.5 Acceleration coefficient,

7 Particle Swarm Optimization, 6., PSO PARC 30 db,. PARC =30, 25,..., 10 db, SNR=0 db [3] [4]., 7 [4] PARC,. (a) (a) Estimation error of (b) (b) Estimation error of (a) (a) Estimation error of (b) (b) Estimation error of 그림 6. SNR Fig. 6. Estimation error of and for various SNRs. 그림 7. PARC Fig. 7. Estimation error of and for various errors of PARC. ALOS 3(i.e. HH VV [8], HH HV ) [1]. corner reflector(cr), CR, HH VV 1, HH VV 0, HH HV 30 db. PARC 30 db SNR=30 db 655

8 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 30, no. 8, Aug 표 2. ALOS [1] Table 2. Comparison of proposed method and conventional methods versus requirements for performance of polarimetric calibration of ALOS [1]. Items of ALOS Conventional method of ref. [3] Conventional method of ref. [4] Proposed method Requirements of ALOS [1] VV/HH amplitude ratio ±0.047 VV/HH phase difference HV/HH power ratio db db dB 30 db, 2. channel imbalance, HH VV ALOS (i.e. 1±0.047). PARC,.. 결론 SAR, 3 PARC 1 PARC PSO 2. SAR, reciprocity theorem azimuth symmetry [2],[3],[6] PARC [4],[5],. References [1] M. Shimada, A. Freeman, "A technique for measurement of spaceborne SAR antenna patterns using distributed targets," IEEE Transactions on Geoscience and Remote Sensing, vol. 33, no. 1, pp , Jan [2] D. Yang, J. M. Shin, S. Jung, I. Choi, and S. Park, "Polarimetric calibration of satellite SAR images," in International Symposium Remote Sensing (ISRS) 2018, Pyeongchang, May [3] S. Quegan, "A unified algorithm for phase and cross-talk calibration of polarimetric data-theory and observations," IEEE Transactions on Geoscience and Remote Sensing, vol. 32, no. 1, pp , Jan [4] S. H. Yueh, J. A. Kong, R. M. Barnes, and R. T. Shin, "Calibration of polarimetric radars using in-scene reflectors," Journal of Electromagnetic Waves and Application, vol. 4, no. 1, pp , [5] M. Fujita, "Polarimetic calibration of the SIR-C C-band channel using active radar calibrators and polarization selective dihedrals," IEEE Transactions on Geoscience and Remote Sensing, vol. 36, no. 6, pp , Nov [6] A. Villa, L. Iannini, D. Giudici, A. Monti-Guarnieri, and S. Tebaldini, "Calibraion of SAR polarimetric images by means of a covariance matching," IEEE Transactions on Geoscience and Remote Sensing, vol. 53, no. 2, pp , Feb [7] M. S. Kang, S. H. Lee, S. H. Park, S. Y. Shin, E. Yang, and, K. T. Kim, "Inter-pulse motion compensation of an ISAR image generated by stepped chirp waveform using improved particle swarm optimization," The Journal of Korean Institute of Electromagnetic Engineering and 656

9 Particle Swarm Optimization Science, vol. 26, no. 2, pp , Feb [8] G. Chang, Y. S. Oh, "Polarimetric SAR image classification based on the degree of polarization and copolarized phase-difference statistics," The Journal of Korean Institute of Electromagnetic Engineering and Science, vol. 18, no. 12, pp , Dec [/] : () : ( ) : [ 주관심분야 ],,,, [/] : () : () : () : [ 주관심분야 ], EMI/EMC,,, [ /] : ( ) : () : () : [ ] ISAR, [/] : ( ) : ( ) : () : [ 주관심분야 ] SAR,, InSAR, Stereo Vision 657

10 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 30, no. 8, Aug [/] : () : () : () : Center for Space Research, SAR : [ 주관심분야 ] SAR, SAR/InSAR/PolSAR [/] : () : () : () : : : /IR : [ 주관심분야 ],, RCS 658