An Innovative Spaceborne SAR Concept With Low PRF: Using Intra-Pulse Doppler Effects for Doppler Spectrum Recovery

Abstract:
This paper describes a new spaceborne synthetic aperture radar (SAR) concept, in which the equivalent pulse repetition frequency (PRF) is significantly lower than the processed Doppler bandwidth. The concept exploits the different intrapulse Doppler effects caused by the varying relative velocity between the satellite and a target to recover the Doppler spectrum. When the spectrum of the transmitted pulse is sparse and contains only pure tones, the received tones are shifted with the different intra-pulse Doppler effects, and the azimuth undersampling results in back-folding instead of aliasing. Hence, the intra-pulse Doppler effects enable the recovery of the Doppler spectrum for the low PRF SAR concept and substantially improve the acquisition capability of a spaceborne SAR system.