Abstract: It is very difficult to detect micro-motion targets against a strong ground clutter background. In order to solve this problem, this paper proposes respectively the methods of dual-channel synthetic aperture radar/displaced phase center antenna (SAR/DPCA) and along-track interferometry (ATI) based on a detailed study of the echo features of rotating targets in the range-compressed data domain. Under the mode of SAR/DPCA, the entire micro-Doppler (m-D) signature undergoes a shift along the frequency axis which is proportional to the azimuth position of the revolving center. Therefore, the target can be located while the micro-motion parameters are estimated. Under the mode of SAR/ATI, the m-D signature cannot be directly obtained from the imaginary part of the interferometric signal by time-frequency transform, so a method is proposed of reconstructing the complex signal of a rotating target based on the imaginary part. In order to avoid m-D ambiguity, the paper points out that when the length of baseline is comparatively short, the method of SAR/ATI is more suitable for detecting targets with big rotating blades than the method of SAR/DPCA, because it requires lower pulse repetition frequency (PRF), The results of simulation tests for these modes testify the validity of the theoretical analysis and the proposed methods.

Key words: synthetic aperture radar, displaced phase center antenna, along-track interferometry, micro-Doppler, time-frequency transform