Impact of antenna beam granularity on sliding spotlight spaceborne SAR image quality

Antenna beam in sliding spotlight spaceborne synthetic aperture radar (SAR) cannot continuously scan the illuminated scene, leading to paired-echo in SAR images. A method quantitatively analyzing the impact of antenna beam granularity was presented. Firstly, mathematical mode of sliding spotlight spaceborne SAR was proposed based on the azimuth antenna beam granularity. Then, the qualitative and quantitative studies about the impacts of antenna beam granularity on image quality were proposed. And the expression for determining both amplitudes and positions of paired-echo and the minimum beam granularity was illuminated. Moreover, the impacts of paired-echo on azimuth resolution, integrated side lobe ratio (ISLR), peak side lobe ratio (PSLR) and system gain were discussed, at different operation frequencies, e. g. X-band and C-band. Therefore, the analysis provides a theoretical basis for minimum antenna beam granularity design. Finally, computer simulations testify to the validity of theoretical analysis.