Signal properties of spaceborne squint-mode SAR

This paper presents signal properties of spaceborne, strip-map SAR for very large squint angles. Doppler centroid, azimuth bandwidth, and exposure time are derived in terms of the platform attitude and elevation angle. This allows a description of the Doppler centroid variation with range and terrain height, and explains a possible range dependence of azimuth bandwidth at high squint. The yaw and pitch required to minimize Doppler centroid and azimuth bandwidth variation are derived, and residual Doppler centroid variation in the presence of antenna pointing errors is presented. The SAR constraint on the relationship between swath width and azimuth bandwidth is revisited for high squint, and is used to present a fundamental limit on squint angle. Finally, processing considerations arising from the shape of the two-dimensional (2D) spectrum with high squint are discussed.