Range Ambiguity Suppression in Space-Borne SAR by Up- and Down-Chirp Modulation in Combination with Pseudo-Random Bi-Phase Coding

Abstract:
With conventional SAR, unambiguous stripmap imaging of a wide swath requires an antenna that meets the minimum antenna area constraint and has a high length to width ratio. A novel range ambiguity suppression technique proposed in this paper will relax the minimum antenna area constraint by a factor 2 in the specific case of a maritime scenario with low backscattering throughout the scene, except for a limited number of bright targets. The method involves the use of up- and down-chirp modulation for spreading of the unwanted energy in range, in combination with pseudo-random bi-phase coding for spreading in azimuth.