Unambiguous SAR imaging algorithm via spotlight mode for multichannel SAR systems

Azimuth multichannel synthetic aperture radar (SAR) systems are capable of high-resolution and wide-swath (HRWS) imaging. This paper presents a novel unambiguous SAR imaging algorithm via spotlight mode for multichannel SAR systems. It's derived that the least unambiguous pulse repetition frequency (PRF) is the function of azimuth width of the illuminated area. By constructing spotlight SAR signals via digital beamforming (DBF) from multiple azimuth receivers, the wide azimuth imaging area can be divided into multiple narrow azimuth areas. Therefore, the least unambiguous PRF for the generated spotlight SAR signals could be reduced and unambiguous SAR images can be obtained by spotlight SAR imaging algorithms. Theoretical analysis and experiments based on real measurements from an airborne multichannel SAR system showed the simplicity and efficiency of the proposed imaging method.