Nonuniform Frequency Sampling Technique for Near-Field Scattering Measurements
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摘要: 传统频率步进 (Stepped frequency, SF)测量体制通过一组等间隔的离散点频信号合成大测量带宽。由于采样定理的限制,固定频率间隔数据所对应的时域信号将会呈周期出现,此时场地内的背景、多径干扰都有可能混叠至目标区域内,进而对成像和散射测量造成恶劣影响。围绕频率步进体制快速测量方法进行了探索,提出了一种基于非均匀采样的近场散射测量技术。分析了距离混叠效应对散射测量的影响,根据实际应用需求设计了采样函数的优化原则,通过泊松和公式与驻定相位原理(Principle of stationary phase, POSP)对信号包络进行赋形。针对传统非均匀采样重构方法所造成的散射图像退化问题,提出了一种与非均匀采样策略相适配的加权方法,在有效抑制混叠干扰的同时实现了高分辨率成像,并提升了近远场变换(Near Field to Far Field, NF-FF)的精度。Abstract: Traditional stepped frequency (SF) systems synthesize a large measurement bandwidth using a series of equidistant discrete frequency signals. However, due to sampling theorem limitations, time-domain signals corresponding to fixed frequency intervals exhibit periodicity. Consequently, background and multipath interference in the measurement environment may alias into the target area, adversely affecting imaging and scattering measurements. This paper explores rapid measurement methods for frequency-stepped systems and proposes a near-field scattering measurement technique based on nonuniform sampling. We analyze the impact of range ambiguity on scattering measurements and design optimization principles for the sampling function based on practical application requirements. The signal envelope is shaped using Poisson's formula and the principle of stationary phase (POSP). To address scattering image degradation caused by traditional nonuniform sampling reconstruction methods, we propose a weighted method compatible with the nonuniform sampling strategy. This method effectively suppresses aliasing interference, achieves high-resolution imaging, and improves the accuracy of near-field to far-field (NF-FF) transformations.
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表 1 三种频率分布的典型频率值(GHz)
Table 1. Typical frequency values of three frequency distributions
频率分布 n=1 n=51 n=101 n=151 n=201 均匀 10.00 11.00 12.00 13.00 14.00 指数 10.00 10.72 11.48 12.31 13.19 加权平方根 10.00 11.40 12.64 13.78 14.82 频率分布 n=251 n=301 n=351 n=401 n=451 均匀 15.00 16.00 17.00 18.00 19.00 指数 14.13 15.14 16.23 17.39 18.64 加权平方根 15.80 16.72 17.59 18.43 19.22 -
[1] 何国瑜. 电磁散射的计算和测量[M]. 北京: 北京航空航天大学出版社, 2006. [2] Xu X, Narayanan R M. Three-dimensional Interferometric ISAR Imaging for Target Scattering Diagnosis and Modeling[J]. IEEE Transactions on Image Processing, 2001, 10(7): 1094-1102. doi: 10.1109/83.931103 [3] Tan K, Chen X. Fast 3-D image reconstruction on nonregular UWB sparse MIMO planar array using scaling techniques[J]. IEEE Trans. Microwave Theory and Technique, 2021, 69(1): 222-234. doi: 10.1109/TMTT.2020.3019099 [4] Luo H, Zhu Z, Jiang M, et al. An effective multipath ghost recognition method for sparse MIMO radar[J]. IEEE Transactions on Geoscience and Remote Sensing, 2023, 61: 1-11. [5] Xiang Y, Guo S, Xia S, et al. NLOS target positioning method based on UAV millimeter-wave radar[J]. IEEE Sensors Journal, 2024, 24(2): 1975-1987. doi: 10.1109/JSEN.2023.3338508 [6] Kornprobst J, Knapp R, Mauermayer M M, et al. Accuracy and conditioning of surface-source based near-field to far-field transformations[J]. IEEE Transactions on Antennas and Propagation, 2021, 69(8): 4894-4908. doi: 10.1109/TAP.2020.3048497 [7] Lahaie I J. An Improved version of the circular near field-tofar field transformation (CNFFFT)[C]. Proceedings of the 27th Annual Meeting of the Antenna Measurement Techniques Association, 2005. [8] Saurer M, Hofmann B, Eibert T F. A fully polarimetric multilevel fast spectral domain algorithm for 3-D imaging with irregular sample locations[J]. IEEE Transactions on Microwave Theory and Techniques, 2022, 70(9): 4231-4242. doi: 10.1109/TMTT.2022.3187984 [9] Sun X, Wu Y, Zhang L, et al. Stepped frequency waveform optimization for formation targets detection[J]. IEEE Geoscience and Remote Sensing Letters, 2022, 19: 1-5. [10] Zhao L, Liu Y. Ballistic target recognition based on 4-D point cloud using randomized stepped frequency radar[C]. IEEE Transactions on Aerospace and Electronic Systems, 2022. [11] Liu S, Cao Y, Yeo T S, et al. Adaptive clutter suppression in randomized stepped-frequency radar[J]. IEEE Transactions on Aerospace and Electronic Systems, 2021, 57(2): 1317-1333. doi: 10.1109/TAES.2020.3040530 [12] 许小剑. 雷达目标散射特性测量与处理新技术[M]. 北京: 国防工业出版社, 2017. [13] Wang L, Huang T, Liu Y. Randomized stepped frequency radars exploiting block sparsity of extended targets: A theoretical analysis[J]. IEEE Transactions on Signal Processing, 2021, 69: 1378-1393. doi: 10.1109/TSP.2021.3058444 [14] Lyu M, Chen H, Yang J, et al. Sensing matrix optimization for random stepped-frequency signal based on two-dimensional ambiguity function[J]. Chinese Journal of Electronics, 2024, 33,(1): 161-174. doi: 10.23919/cje.2022.00.046 [15] Gumbmann F, Schiessl A. Multistatic Short Range Imaging with a Nonuniform SFCW Concept[C]. Asia Pacific Microwave Conference-Proceedings, 2014. [16] Gumbmann F, Schiessl A. Short-range Imaging System with a Nonuniform SFCW Approach[J]. IEEE Transactions on Microwave Theory and Techniques, 2017, 65(4): 1345-1354. doi: 10.1109/TMTT.2017.2649501 [17] Liu C, Li Z, Sun Q, et al. Three-dimensional sparse image reconstruction for terahertz surface layer holography with random step frequency[J]. Optics Letter, 2015, 40(14): 3384-3387. doi: 10.1364/OL.40.003384 [18] Axelsson S R J. Analysis of random step frequency radar and comparison with experiments[J]. IEEE Transactions on Geoscience and Remote Sensing, 2007, 45(4): 890-904. doi: 10.1109/TGRS.2006.888865 [19] Gurbuz A C, Mcclellan J H, Scott W R. A compressive sensing data acquisition and imaging method for stepped frequency GPRs[J]. IEEE Transactions on Signal Processing, 2009, 57(7): 2640-2650. doi: 10.1109/TSP.2009.2016270 [20] Ma Y, Hong H, Zhu X. Multiple moving-target indication for urban sensing using change detection-based compressive sensing[J]. IEEE Geoscience and Remote Sensing Letters, 2021, 18(3): 416-420. doi: 10.1109/LGRS.2020.2977168 [21] Gallet M, Mian A, Ginolhac G, et al. New robust sparse convolutional coding inversion algorithm for ground penetrating radar Images[J]. IEEE Transactions on Geoscience and Remote Sensing, 2023, 61: 12-14. [22] Wu Q, Lai Z, Amin M G. Through-the-wall radar imaging based on bayesian compressive sensing exploiting multipath and target structure[J]. IEEE Transactions on Computational Imaging, 2021, 7: 422-435. doi: 10.1109/TCI.2021.3071957 [23] Bi D J, Xie Y L, Ma L, et al. Multifrequency compressed sensing for 2-D near-field synthetic aperture radar image reconstruction[J]. IEEE Transactions on Instrumentation and Measurement, 2017, 66(4): 777-791. doi: 10.1109/TIM.2017.2654578 [24] Ishimaru A, Chen Y S. Thinning and broadbanding antenna arrays by unequal spacings[J]. IEEE Transactions on Antennas and Propagation, 2003, 13(1): 34-42. [25] Chow Y L. On grating plateaux of nonuniformly spaced arrays[J]. IEEE Transactions on Antennas and Propagation, 1965, 13(2): 208-215. doi: 10.1109/TAP.1965.1138391 [26] Si W, Zhuge X. A nonuniform SFCW scheme for short range application[C]. 2020 International Conference on Microwave and Millimeter Wave Technology (ICMMT), 2020. [27] 胡楚锋. 雷达目标 RCS 测试系统及微波成像诊断技术研究[D]. 西安: 西北工业大学,2007. [28] Luminati J E, Hale T B, Temple M A, et al. Doppler aliasing artifact filtering in SAR imagery using randomised stepped-frequency waveforms[J]. Electronics Letters, 2004, 40(22): 1447-1448. doi: 10.1049/el:20046440 [29] Martorella M, Giusti E, Demi L, et al. Target recognition by means of polarimetric ISAR images[J]. IEEE Transactions on Aerospace and Electronic Systems, 2011, 47(1): 225-239. doi: 10.1109/TAES.2011.5705672 [30] Vaupel T, Eibert T F. Comparison and application of Near-Field ISAR imaging techniques for far-field radar cross section determination[J]. IEEE Transactions on Antennas and Propagation, 2006, 54(1): 144-151. doi: 10.1109/TAP.2005.861549 [31] Zhang Y X, Jiao Y C, Zhu M D, et al. A linear-scan-based wideband single-cut near-field RCS measurement technique with wide effective angle coverage[J]. IEEE Antennas and Wireless Propagation Letters, 2023, 22(9): 2300-2304. doi: 10.1109/LAWP.2023.3286481 [32] Watanabe T. Image-based radar cross section synthesis for a cluster of multiple static targets[J]. IEEE Transactions on Instrumentation and Measurement, 2023, 72: 1-13. -