Performance Analysis on ISAR Imaging of Space Targets
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摘要: 空间目标逆合成孔径雷达(ISAR)成像的方位维相干积累增益取决于目标运动状态信息,关于目标运动分析的缺失将直接影响空间目标ISAR观测中成像质量的预估与系统参数的设计。该文提出根据空间目标轨道参数计算其相对雷达视线运动状态,推导一定相干积累角ISAR成像的方位相干积累简化公式,实现基于相干积累角的ISAR成像时间段选择,可有效保证成像方位分辨率;同时详细分析目标轨道高度等参数对ISAR系统回波接收功率、成像质量的影响,为空间目标ISAR成像雷达体制设计提供了设计依据。理论推导和仿真实验均验证了空间目标ISAR成像中随着目标轨道高度升高,单次回波信噪比降低的损失可通过方位相干积累增益的提升实现部分弥补。该文工作可为空间目标ISAR成像体制和处理设计提供了理论基础和指标设计依据。Abstract: Usually, in traditional Inverse Synthetic Aperture Radar (ISAR) systems design and mode selection for space satellite targets, coherent integration gain in azimuth direction hardly can be analyzed, which depends on target’s motion. In this study, we combine the target orbit parameters to determine its motion relative to radar and deduce coherent integration equation in ISAR imaging to realize the selection of imaging intervals based on coherent integration, which can ensure the resolution in azimuth direction. Meanwhile, we analyze the influence of target orbit altitude to echo power and imaging Signal-to-Noise Ratio (SNR) that provides a new indicator for space observation ISAR systems design. The result of simulation experiment illustrates that with target orbit altitude increasing, coherent integration gain in azimuth direction of large-angular observation offsets the decreasing of imaging SNR in a degree, which provides a brand-new perspective for space observation ISAR systems and signal processing design.
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表 1 实验ISAR系统主要参数
Table 1. Main parameters of ISAR system
参数 数值 载频 16.7 GHz 带宽 1 GHz 方位向分辨率 0.18 m 距离向分辨率 0.15 m 脉冲重复频率 200 Hz 表 2 实验地基ISAR观测站位置
Table 2. Position parameters of radar sites
地点 经纬度 库尔勒 41.5°N, 86.8°E 北京 39.9°N, 116.4°E 西安 31.1°N, 108.4°E 表 3 不同轨道高度图像质量评价
Table 3. Comparison result of imaging quality at different heights
轨道高度(km) 成像时间(s) 脉冲积累数 TNR 脉冲积累数/TNR 791 9.94 1988 6.82 291.58 1200 12.40 2484 8.61 288.58 1800 16.82 3364 11.45 293.80 -
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