Coherence improving algorithm for airborne multichannel SAR-GMTI

The study develops an algorithm to improve coherence for the multichannel airborne along-track synthetic aperture radar (SAR), which can be used for ground moving target indication (GMTI) by comparing two SAR images obtained from different channels. The turbulent aircraft motion, beam pattern difference and frequency response difference that may degrade the coherence are discussed in detail. The aircraft motion error is firstly estimated and corrected based on the range compressed data. After focusing on the beam pattern differences and the receive channel imbalance are compensated using the two two-dimensional (2-D) adaptive filters, the first in the range-Doppler domain and the second in the range-frequency azimuth-time domain. It is shown that using the coherence improving algorithm the coherence of SAR complex image pairs can be improved greatly. The effectiveness of the algorithm is demonstrated with real data acquired by a Chinese X-band multichannel airborne SAR-GMTI system.