SAR Ground Moving Target Indication via Cross-Track Interferometry for a Forward-Looking Array

In this paper, an effective synthetic aperture radar ground moving target indication (SAR-GMTI) method is proposed based on cross-track interferometry only, by combining the squint-looking and a 2-D cruciform forward-looking array. First, for a multiple-channel SAR with an arbitrarily array configuration and an arbitrary-looking angle, the 2-D response of a ground moving target, including its phase, amplitude, and position, is derived in the complex image domain via back-projection algorithm. Second, an interferometry phase sensitivity function is defined to evaluate the interferometry properties of an arbitrarily baseline with a closed-form expression, from which the GMTI and altitude-estimating abilities of the conventional along-track baseline and cross-track baseline can be verified. Besides, it is shown that the interferometry phases of the upright cross-track and straightforward along-track baselines are only sensitive to the target's height and velocity, respectively. Furthermore, the interferometry phase of the level cross-track baseline can be sensitive to both target's radial velocity and height when the squint-looking angle is large. Therefore, to solve the coupled phases of velocity and height of the moving target in a real fluctuating terrain, a cruciform cross-track baseline with five receiving channels is further proposed for a squint-looking SAR, by which the height, radial velocity, and location of both fixed and moving targets can be estimated, simultaneously. This means that the SAR-GMTI can be effectively accomplished by cross-track interferometry only without along-track baseline. Finally, some results of numerical experiments are provided to demonstrate the effectiveness of the proposed method.