Concise formula derivation for ground-range-resolution improvement by InSAR

Two approaches were presented to show the improvement of ground resolution by cross-track interferometric SAR. In the first approach, an equivalent relation was firstly derived between the usual stepped-frequency chirp signal (SFCS) and the SFCS with all subchirps transmitted at different positions (SFCS_DP) when some condition was contented during matched filtering, and then the signal model of InSAR in ground direction was shown to be equivalent to that of SFCS_ DP, and finally an broadened spatial spectrum observed in ground direction was derived. In the second approach, the projection of wave number k in ground direction was used to derive the widening of observed spatial spectrum. Simulations showed that the relative error of range measurements between two channels had remarkable influence on the final result.