ISAR Imaging of Multiple Targets With Time-Delay Receive Array

For inverse synthetic aperture radar (ISAR), it is desirable to perform simultaneously imaging of multi-target within a wide spatial angle region. Besides, it is likely that multiple targets are covered by several beams, or sometimes within a single beam, which results in imaging challenge for each single target. To alleviate this problem, this paper devises a new approach by introducing time delay across different receive array elements, realizing multi-target separation and independent imaging. By using the time-delay receive array with linear frequency modulation (LFM) waveform, the equivalent receive beampattern is range-angle-dependent and it is possible to perform beamforming in joint range and angle domain. In the time-delay receive array, an element compensation method is presented to cope with the variation of the equivalent spatial frequency. After receive beamforming, the conventional high resolution ISAR imaging method can be performed. With the proposed method, the multi-target echo can be separated under low signal noise ratio (SNR). Simulation results have verified the effectiveness of the proposed approach.