径向速度对频率步进雷达目标距离像影响分析
Analysis of radial velocity effect on range profile of stepped-frequency waveform
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摘要: 脉间频率步进波形是一种高距离分辨率信号形式,它通过子脉冲载频的步进变化来获得大的有效带宽,显著降低了系统的瞬时带宽和对接收机硬件的要求。但该信号对目标径向速度非常敏感,雷达与目标间的径向运动将造成距离像峰值的移动、衰减和发散。该文深入分析了目标径向速度对频率步进雷达一维合成距离像的影响,推导出不同距离取样分辨率条件下的距离像偏移因子和发散因子表达式。通过对复数距离像相位的分析,证明了采用补零法来增加逆傅里叶交换点数只能提高距离取样分辨率,而不会影响雷达的距离分辨率。Abstract: Stepped-frequency is a kind of high range resolution waveform, which is used to obtain broad effective bandwidth by sequentially changing of carrier frequency over sub-pulses in one burst, so it reduces requirements on instantaneous bandwidth and receiver. However, this waveform is so sensitive to radial velocity between radar and targets that the loss of range resolution and loss of SNR are brought to SAR system. In the paper, the effect of radial velocity on synthetic range profile is discussed thoroughly first, then two important parameters, target range shift and range spread, are defined in terms of the phase of synthetic range function. Furthermore, the enhancement of the range sample resolution only makes the synthetic range profile present more details, but it will not change the range resolution.
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D.R. Wehner, High Resolution Radar (2nd ed), London, Artech House, 1994, Chaper5.[2]R.T. Lord, M. R. Inggs, High resolution VHF SAR processing using synthetic range profiling.Proc. IEEE Geoscience Remote Sensing Symp., IGARSS96, Lincoln, Nebraska, June 1996, vol.1.454-456.[3]G.S. Gill, Step frequency waveform design and processing for detection of moving targets in clutter, IEEE International Radar Conference, Washington D. C., May 1995, 573-578.[4]安建平,张润宁,白克壮,应用于SAR的一种波形及多普勒效应补偿技术,系统工程与电子技术,2000,22(1),59-62.[5]K. Ruttenberg, et al., High range resolution by means of pulse to pulse frequency shifting, EASCON68 Record, Washington D. C., Sep. 1968, 47-51.[6]张澄波,综合孔径雷达原理、系统分析与应用,北京,科学出版社,1989,30-33.[7]吴湘淇,信号、系统与信号处理(上),北京,电子工业出版社,1996,118-122. -
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