Investigation on Electronic Azimuth Beam Steering in the Spaceborne Sar Imaging Modes

This paper reviews different spaceborne SAR imaging modes with electronic azimuth beam steering adopted for greater azimuth resolution in spotlight/sliding spotlight mode and wider swath coverage in TOPS (Terrain Observation by Progressive Scans) mode. However, the use of electronic beam steering via a planar phased antenna, especially in the spaceborne SAR system, leads to a quantization of the beam steering law, grating lobes and main lobe gain reduction. The distorted synthetic azimuth antenna pattern (AAP) due to angle quantization and squinted angle will affect system performances. These effects in different imaging modes are analyzed in detail for the design of future spaceborne SAR missions.