Out-of-Band Ambiguity Analysis of Nonuniformly Sampled SAR Signals

High-resolution and wide-swath synthetic aperture radar (SAR) images can be obtained by multichannel sampling. However, a nonoptimum pulse-repetition frequency is associated with a nonuniform spatial sampling in azimuth. A spectrum reconstruction algorithm and a filter group algorithm can be used to reconstruct the spectrum in azimuth with a nonuniform sampling. In this letter, a comparison of spectrum reconstruction algorithm and filter group algorithm is given. Through a transformation matrix, the relationship between out-of-band signals and the out-of-band signals after reconstruction is built. Furthermore, an equivalent spectrum after reconstruction is obtained, and simulation results proved that it is precise. From the equivalent spectrum, it shows that multichannel SAR can be seen as uniform sampling system but with a different original signal. Finally, channel imbalance is discussed. Simulation results have proved that the imbalance targets have the same location with corresponding ambiguous targets.