Radial Velocity Retrieval for Multichannel SAR Moving Targets With Time–Space Doppler Deambiguity

In this paper, with respect to multichannel synthetic aperture radar (SAR), we first formulate the problems of Doppler ambiguities on the radial velocity (RV) estimation of a ground moving target in the range-compressed domain, the range-Doppler domain, and the image domain, respectively. It is revealed that in these problems, the cascaded time–space Doppler ambiguity (CTSDA) may arise; that is, the time domain Doppler ambiguity in each channel arises first and then the spatial domain Doppler ambiguity among multichannels arises second. Accordingly, the multichannel SAR systems with different parameters are investigated in three cases with different Doppler ambiguity properties. Then, a multifrequency SAR is proposed for the RV estimation by solving the ambiguity problem based on the Chinese remainder theorem (CRT). In the first two cases, the ambiguity problem can be solved by the existing closed-form robust CRT. In the third case, it is found that the problem is different from the conventional CRT problem and we call it a double remaindering problem in this paper. We then propose a sufficient condition under which the double remaindering problem, i.e., the CTSDA, can also be solved by the closed-form robust CRT. When the sufficient condition is not satisfied, a searching-based method is proposed. Finally, some results of numerical experiments are provided to demonstrate the effectiveness of the proposed methods.