Back projection algorithm for spotlight bistatic SAR imaging

Bistatic radar, spatially separated between the transmitter and receiver, has recently been an interesting research hotspot. As geometry configurations of bistatic SAR can be flexible, its slant range is more complicated than the monostatic SAR case. Furthermore, in the spotlight-mode, the angle between the transmitter/receiver platform and the scenes center is higher than the strip-mode case. Hence, range migration in spotlight-mode BiSAR is more severe than the strip-mode BiSAR case. Solving Range migration problem is key step to develop the spotlight-mode BiSAR imaging formation. In this paper, we derive the dechirp formula of bistatic SAR as range compression is usually implemented by dechirped method in spotlight SAR. Then we establish the BiSAR echoes model and analyze the principle of back projection algorithm. By analyzing the principle of back projection algorithm, we can see that back projection algorithm is adapt to general aperture configure, and compensating for range migration easily in the time domain. Under the condition of the different bistatic angles, we give the simulation results to validate that impulse response of point target is compressed well by the back projection algorithm.