A Novel Azimuth Multichannel Reconstruction Approach for Moving Targets in Multichannel Sliding Spotlight SAR

Sliding spotlight SAR combined with the multichannel receiving technology has the ultra-high resolution wide swath imaging capacity. Since the range history and Doppler characteristics of moving targets are different from those of fixed targets, the moving target echo model in multichannel sliding spotlight SAR is established in this paper. The azimuth velocity component of the moving target would results in azimuth defocusing, while the slant range velocity component would lead to pairs of false targets. In this paper, a novel azimuth multichannel reconstruction method for moving targets is proposed according to the multichannel signal model. First, the instantaneous Doppler centroid of each channel is removed by de-ramp preprocessing to reduce the total Doppler bandwidth of the whole imaged scene. Afterwards, the azimuth non-uniform sampling problem is resolved by the modified multichannel reconstruction matrix corresponding to the velocity of the moving target. Finally, the Doppler spectrum is recovered by the azimuth inverse de-ramp operation. The proposed method resolves the problem of Doppler spectrum aliasing caused by azimuth beam scanning and avoids the up-sampling processing with the large amount of zero padding. Furthermore, the modified reconstruction matrix is used to match the multi-channel Doppler characteristics of moving targets in multichannel sliding spotlight. Simulation results of moving targets validate the proposed azimuth multichannel reconstruction approach.