Abstract: The extended SIM algorithm for translational invariant bistatic SAR imaging is proposed.Firstly,the power ambiguity problem of squint bistatic SAR is solved by using the azimuth Doppler frequecy demodulation.Then the two-dimensional spectrum of the azimuth demodulated signal is derived,and the new match filtering functions are composed based on it.Finally,the validity of the algorithm is tested by the simulation,and the enhancement of image quality by the new algorithm is analyzed.