Spatial Resolution of Bistatic Synthetic Aperture Radar: Impact of Acquisition Geometry on Imaging Performance

This paper analyzes the spatial resolution of bistatic synthetic aperture radar (SAR) in general hybrid configurations, such as air- and spaceborne systems moving along independent trajectories. The gradient method is utilized to point out the effects of the acquisition geometry, namely, position and velocity of both the transmitter and the receiver, on image resolution. This general approach is applied to different realizations of bistatic SAR, such as low-Earth-orbit monostatic-bistatic SAR, spaceborne-airborne bistatic SAR, and a bistatic system consisting of a high-altitude long-endurance illuminator and lower altitude airborne receivers. The main features of the method are then put in evidence, including the derivation of analytical tools to individuate adequate relative geometries for achieving satisfactory resolutions. A comparison to the other proposed techniques for computing the spatial resolution of bistatic SAR is also reported in order to highlight some peculiarities of all presented methodologies. Finally, the good agreement between the image resolution results achieved by recently carried out bistatic SAR experiments and the ones derived by the gradient method strengthens the potentialities of the proposed approach.