Azimuth ambiguity suppression with an improved reconstruction method based on antenna pattern for multichannel synthetic aperture radar systems

For synthetic aperture radar (SAR) systems, antenna array which is distributed in flight direction could increase the equivalent sample frequency in azimuth by a factor of the number of elements of antenna array. With a reconstruction algorithm, the aliased Doppler spectrum could be recovered. However, the degradation of conventional algorithms for reconstructing the Doppler spectrum with special pulse repetition frequency (PRF) shows poor robustness and the out-of-band energy which is caused by the side lobes of the antenna pattern deteriorates the azimuth ambiguity to signal ratio of a multichannel SAR. In this study, an improved reconstruction algorithm based on antenna pattern is proposed by generating an ambiguity matrix, which resembles the covariance matrix and could be used to reconstruct in-band signal and minimise the azimuth ambiguity energy. Aiming at increasing the robustness of the algorithm, the method of diagonal loading is introduced to the approach. Even in the scenario of special PRF, which is close to the singular point, the signal could be successfully reconstructed with the improved approach. Simulation results validate the proposed method.