Analog I/Q modulation technology is one of the most commonly used and important technical means in broadband synthetic aperture radar (SAR) exciter design. With the increasing instantaneous bandwidth of radar system, the amplitude-phase consistency of analog I/Q modulation can not be completely guaranteed by the symmetrical characteristics of devices, and the spurious distortion caused by the IQ imbalance in broadband radar transmission system will deteriorate progressively. This paper proposes a digital predistortion method which can extract all amplitude-phase errors on the whole transmission channel， mainly including IQ imbalance， by modeling the system error and building a test system, map the amplitude-phase errors to the IQ branch of digital baseband signal output, and compensate the amplitude-phase distortion of the transmission channel. Finally, combined with the actual radar transmitting system, the distortion of the whole transmitting link is corrected by using the predistortion method. The test results before and after correction are given， demonstrating the effectiveness of the method.
JIA Yingxin
,
WANG Yanfei
. A predistortion correction method for quadrature modulation amplitude and phase imbalance of SAR excitation signal[J]. Journal of University of Chinese Academy of Sciences, 2024
, 41(4)
: 524
-532
.
DOI: 10.7523/j.ucas.2022.079
[1] Brenner A R, Essen H, Stilla U. Representation of stationary vehicles in ultra-high resolution SAR and turntable ISAR images[C]//EUSAR 2012; 9th European Conference on Synthetic Aperture Radar. Nuremberg, Germany. VDE: 147-150.
[2] El-Arnauti G, Saalmann O, Brenner A R. Ultra-high resolution airborne experiments with a new Ka-band SAR sensor[C]//2017 European Radar Conference (EURAD). October 11-13, 2017. Nuremberg, Germany. IEEE, 2017: 409-412. DOI:10.23919/eurad.2017.8249234.
[3] Dupuis X, Martineau P. Very high resolution circular SAR imaging at X band[C]//2014 IEEE Geoscience and Remote Sensing Symposium. Quebec City, QC, Canada. IEEE,: 930-933. DOI:10.1109/IGARSS.2014.6946578.
[4] Mishra S, Singh N, Dhar J, et al. A GaAs based miniaturized C-band double balanced resistive IQ modulator for synthetic aperture radar (SAR) applications[C]//2019 IEEE Recent Advances in Geoscience and Remote Sensing: Technologies, Standards and Applications. Kochi, India. IEEE,: 57-60. DOI:10.1109/TENGARSS48957.2019.8976064.
[5] Yahav N, Efendowicz A. Broadband high linearity IQ modulator for direct conversion transmitters[C]//2016 46th European Microwave Conference (EuMC). London, UK. IEEE: 1019-1022.
[6] Zhu Z W, Leung H, Huang X P. Challenges in reconfigurable radio transceivers and application of nonlinear signal processing for RF impairment mitigation[J]. IEEE Circuits and Systems Magazine, 2013, 13(1): 44-65. DOI:10.1109/MCAS.2012.2237143.
[7] Luo J, Kortke A, Keusgen W, et al. A novel adaptive calibration scheme for frequency-selective I/Q imbalance in broadband direct-conversion transmitters[J]. IEEE Transactions on Circuits and Systems II: Express Briefs, 2013, 60(2): 61-65. DOI:10.1109/TCSII.2012.2235735.
[8] Khandelwal A, Verma A. A novel gain, phase and offset calibration scheme for wideband direct-conversion transmitters[C]//2015 IEEE 81st Vehicular Technology Conference. Glasgow, UK. IEEE,: 1-5. DOI:10.1109/VTCSpring.2015.7145633.
[9] Fawzy A, Sun S M, Lim T J, et al. Iterative learning control for pre-distortion design in wideband direct-conversion transmitters[C]//GLOBECOM 2020：2020 IEEE Global Communications Conference. Taipei, China. IEEE,: 1-6. DOI:10.1109/GLOBECOM42002.2020.9322378.
[10] Zhu Z W, Huang X P, Leung H. Joint I/Q mismatch and distortion compensation in direct conversion transmitters[J]. IEEE Transactions on Wireless Communications, 2013, 12(6): 2941-2951. DOI:10.1109/TCOMM.2013.050313.121256.
[11] Zhu Z W, Huang X P, Caron M, et al. Blind self-calibration technique for I/Q imbalances and DC-offsets[J]. IEEE Transactions on Circuits and Systems I: Regular Papers, 2014, 61(6): 1849-1859. DOI:10.1109/TCSI.2013.2290826.
[12] Arriaga-Trejo I A. Estimation of the channel and I/Q imbalances with zero correlation zone sequences and superimposed training[C]//2019 IEEE International Conference on Microwaves, Antennas, Communications and Electronic Systems. Tel-Aviv, Israel. IEEE,: 1-6. DOI:10.1109/COMCAS44984.2019.8958069.
[13] Huang X J, Zhang J A, Guo Y J. Joint transmitter and receiver I/Q imbalance estimation in presence of carrier frequency offset[C]//2015 15th International Symposium on Communications and Information Technologies (ISCIT). Nara, Japan. IEEE,: 209-212. DOI:10.1109/ISCIT.2015.7458344.
[14] 陈雷, 岳光荣, 唐俊林, 等. 基于数字预失真的发射机I/Q不平衡矫正[J]. 电子与信息学报, 2017, 39(4): 847-853. DOI:10.11999/JEIT160581.
[15] 陆必应, 梁甸农. 大时带积线性调频信号源幅相误差分析与校正[J]. 现代雷达, 2004, 26(10): 38-40, 60. DOI:10.16592/j.cnki.1004-7859.2004.10.012.
