Improved Azimuth Multichannel SAR Imaging for Configurations With Redundant Measurements

The traditional spectrum reconstruction algorithm for nonuniform sampling of a displaced phase center antenna (DPCA) synthetic aperture radar (SAR) system can provide an unambiguous recovery of an original signal through the inverse computation of a joint filter matrix. However, when the sampling positions of different receivers coincide spatially, the joint filter matrix will be non-invertible, thus causing the ineffectiveness of the algorithm. This letter proposes a regularized spectrum reconstruction scheme when the pulse repetition frequency of a multichannel system operates on these critical frequencies, as well as in their neighborhoods. First, a low-order regularization of the joint filter matrix is suggested so that the original spectrum of the multichannel system can be recovered more accurately with a decreased number of nonredundant channels´ measurements. Furthermore, in order to improve the output signal-to-noise ratio (SNR) of the reconstruction network, a combinational low-order spectrum recovery scheme is additionally presented, which takes all redundant channels´ samples into account. The optimizations bring significant benefits to both the suppression of aliased ambiguities and the advance of the output SNR of the reconstruction network.