A simple reference point spectrum model and modified Omega-K imaging algorithm for spaceborne/airborne bistatic SAR

An accurate and concise analytic expression of the two-dimensional spectrum and a modified Omega-K is presented in this paper. The proposed spectrum is obtained by utilizing the curve fitting method and the principle of station phase (POSP) for the general bistatic SAR(GBiSAR). Firstly, the range history of SA-BSAR is fitted into a hyperbola function of the sampling time in least square theory(LST). Then the new function of the range history is easy to perform the POSP to obtain the analytic spectrum. Next, based on the concise two-dimensional spectrum, the modified frequency algorithm Omega-K (MWK) is introduced to deal with the echo of SA-BSAR. Due to the range history´s approximation in the derivation of 2D spectrum, the equivalent velocity variable has the non-ignorable space variance for the non-reference points. Therefore, the serious spatial-variant is handled by using the Taylor expansion about the equivalent velocity variable. Then the non-uniform fast Fourier transform is applied to substituting the STOLT interpolation and inverse Fourier transform (IFFT) to enhance focusing performance. Finally, numerical simulations are performed to validate the proposed spectrum and algorithm.