The geometry model of bistatic SAR is shown in Fig. 1. Assume that the transmitter is fixed, and the receiver moves along the -axis direction and works at side looking mode with velocity . , and are the slant range from the transmitter and receiver to ground moving target at , while and stand for the instantaneous slant ranges of the transmitter and receiver from the target. and are the squint angles from the two platforms to the target, is the slow time. , , , and denote the relative lateral and radial velocities between the moving target and platforms, respectively. The velocity of the moving target can be decomposed into and . Thus, the instantaneous slant range is given by Display Formula
(1)According to the geometry of bistatic SAR model with one stationary configuration, we have Display FormulaThus, , , , and is given by Display Formula
(2)Similarly, we have Display Formula
(3)where and represent the angles between , , and , respectively. and are the grazing angles of transmitter and receiver. Obviously, , , and satisfies Display Formula
(4)From Eqs. (2)–(4), one obtains six equations with eight variables, i.e., , , , , , , , and . In order to calculate these variables, range walk and range curvature term are estimated in the following procedures, both of which are the functions of the unknown parameters. In this way, the moving target-related variables can be achieved.