Closed form solutions for the depth of focus of synthetic aperture radar (SAR) maps under maneuvers

Conventional range-Doppler processing of SAR data places limitations on the quality of image (map) which can be achieved under maneuvering platform conditions. A closed-form solution is presented for the radar depth of focus. For the case of spotlight synthetic-aperture radar (SAR) operation using conventional (nonpolar) processing, limits are given on the depth of field achievable using variable PRF (pulse repetition rate) and using variable-range focusing with first-order range correction terms. The use of a variable PRF extends the cross-range depth of focus up to a limit which depends on the aircraft acceleration. Variable-range focusing extends the range depth of focus; implementation using a first-order correction imposes bounds on the achievable depth of focus