Pulse repetition frequency design for geosynchronous SAR in ellipcial orbit

Elliptical orbit and squint mode are widely used in the system design of geosynchronous synthetics aperture radar (GEO SAR) to improve the coverage performance. In this paper, the effects of orbit height variation and squint mode to pulse repetition frequency (PRF) design are analyzed. The orbit height variation causes the variation of nadir interference and beam illumination region, and squint mode produces large range cell migration (RCM). These can induce invalidations of the designed PRF. Based on this, the constraints of nadir interference and transmit interference are updated for GEO SAR, and the effective time for the designed PRF is derived. PRF number required for imaging in one orbital period is analyzed.