Interferometric phase model and numerical simulations of swell for across-track interferometric SAR

An Interferometric phase model of swell for the Across-track Interferometric Synthetic Aperture Radar (XTI-SAR) with ocean surface elevation and velocity bunching is presented. An analytical presentation of swell imaging by XTI-SAR is derived. The imaging mechanism of swell propagating in azimuth direction is further investigated. The ratio of the amplitude of the second harmonic and that of the foundamental wave is used to represent the nonlinearity of the imaging. By comparing the second order harmonic components of XTI-SAR phase and that of ATI-SAR phase, analyzing numerical simulations for different sea states and typical interferometric SAR parameters, it is found that XTI-SAR phase suffers stronger nonlinear distortion than ATI-SAR phase when velocity bunching is weak, so ATI-SAR is more appropriate than XTI-SAR to measure ocean wave. Otherwise, when velocity bunching is strong, ATI-SAR phase suffers stronger nonlinear distortion than XTI-SAR phase, XTI-SAR is more sutiable than ATI-SAR to measure ocean wave.