Study on two-step imaging based on azimuthal dechirp in space-borne sliding spotlight SAR

Based on dechirp processing, the two step imaging can effectively decrease the Doppler bandwidth of the echo in space borne sliding spotlight SAR. In order to overcome the alias of the echo, pulse repeation frequency (PRF) should be larger than the residual Doppler bandwidth of the dechirped azimuth signal, which is the fundamental of the two step imaging algorithm. Firstly, the formula of the residual Doppler band-width (RDB) of dechirped azimuth signal in the range frequency and azimuth time domains, which was related to the transmitted bandwidth, azimuth beam width and the azimuth rotation angle, was derived. Secondly, the influence of the window function of the dechirped azimuth signal in two dimensional time domains was analyzed by introducing range migration, and the derived RDB formula was analyzed and validated. Finally, the simulation results validate the analysis.