Frequency and azimuthal variations of radar cross section and their influence upon low-frequency SAR imaging

Low-frequency SAR requires a highly extended synthetic aperture to give a spatial resolution comparable to that of a microwave SAR. As a result, the azimuth angle of the target is varying significantly along the synthetic aperture path. The signal-bandwidth to carrier-frequency ratio is also much larger compared to conventional microwave SAR, giving a fluctuating target response over the frequency band occupied by the transmitted signal. In this paper, the variations of the radar response with frequency and observation angle and their effects upon SAR imaging are analyzed for Mie-scattering spheres and flat plates. The influence of a reflecting sea or ground surface below the target is also discussed