A continuous PRI variation method for geosynchronous SAR with elliptical orbit

Elliptical orbits are widely used in the system design of geosynchronous synthetics aperture radar (GEO SAR) to improve the temporal resolution. The orbit height variation in the elliptical orbit can cause the variation of nadir interference and beam illumination region. This shortens the available time of a designed pulse repetition interval (PRI) for a specific beam pointing, and multiple PRIs have to be used at different orbital positions. To lengthen the available time, a continuous PRI variation method is introduced in this paper. By varying the PRI with a constant time interval, the acquisition window and transmit interference changes with the variant beam illumination region, which loosen the constraint of the transmit interference. A design example of the proposed method is provided with significantly lengthened available time.