Range ambiguity suppression for multi-channel SAR system near singular points

The technique of multiple apertures in azimuth enables a wide swath synthetic aperture radar (SAR) with high azimuth resolution. In a traditional multi-channel SAR system, a reconstruction algorithm is built to recover the ambiguous Doppler spectrum caused by non-uniform sampling. However, if the system pulse repetition frequency (PRF) is near some specific values, singular points exist in the reconstruction algorithm and therefore the spectrum cannot be recovered correctly. The normal method to avoid the influence of the singular points is to use only part of channels to do the reconstruction algorithm. In this paper a new method is proposed to overcome the singularity of the reconstruction algorithm while suppress the range ambiguity by using the azimuth phase coding (APC) technology. By taking advantage of the “abandoned” channels' signal, a proper azimuth beamformer weight vector can be computed to null out the range ambiguity position which has been shifted by APC technology, thus the range ambiguity is significantly suppressed while the useful signal is well recovered. Moreover, the simulation results are presented to validate the effectiveness of the proposed method.