A physical explanation of SAR phase function in two dimensional wavenumber domain

The phase function of an SAR signal in the two dimensional wavenumber domain is usually derived by using the principal of stationary phase. From this phase function, the phase error of the conventional range-Doppler algorithm when used for high resolution large squint angle SAR imaging is obvious [Bamler 1992]. The secondary range compression and other approximate wavenumber domain algorithm can be derived based on the phase function. But the physical meaning of the secondary range compression can not be directly perceived. In this paper we derive the phase function from SAR imaging geometry by using the Doppler-azimuth coordinate relationship in different RF frequency. From this point of view, it is easy to understand the phase error originated from the range-Doppler algorithm