Time-varying complex spectral estimation with applications to ISAR imaging

Complex spectral estimation is very important for improving the target detection and classification capability from complex SAR/ISAR (synthetic aperture radar/inverse synthetic aperture radar) images. In ISAR, due to the noncooperative motion of maneuvering targets, the Doppler shifts are often time-varying during the coherent integration time. In this case, ISAR imaging algorithms based on the range-Doppler processing will produce blurred images. In this paper, we present a recursive APES (amplitude and phase estimation) algorithm for the time-varying complex ISAR image formation of maneuvering targets, which is computationally efficient. Both numerical and experimental examples show that the proposed method significantly outperforms the short-time Fourier transform (STFT) approach.