Bistatic Synthetic Aperture Radar Imaging Using UltraNarrowband Continuous Waveforms

We consider synthetic aperture radar (SAR) imaging using ultranarrowband continuous waveforms (CWs). Because of the high Doppler resolution of CW signals, we refer to this imaging modality as Doppler synthetic aperture radar (DSAR). We present a novel model and an image formation method for the bistatic DSAR for arbitrary imaging geometries. Our bistatic DSAR model is formed by correlating the translated version of the received signal with a scaled or frequency-shifted version of the transmitted CW signal over a finite time window. High-frequency analysis of the resulting model shows that the correlated signal is the projections of the scene reflectivity onto the bistatic iso-Doppler curves. We next use microlocal techniques to develop a filtered-backprojection (FBP) type image reconstruction method. The FBP inversion results in the backprojection of the correlated signal onto the bistatic iso-Doppler curves as opposed to the bistatic iso-range curves used in the traditional wideband SAR imaging. We show that our method takes advantage of the velocity, as well as the acceleration of the antennas in certain directions, to form a high-resolution SAR image. Our bistatic DSAR imaging method is applicable for arbitrary flight trajectories and nonflat topography, and can accommodate system-related parameters. We present resolution analysis and extensive numerical experiments to demonstrate the performance of our imaging method.