Region-Enhanced Passive Radar Imaging

We adapt and apply a recently-developed region-enhanced synthetic aperture radar (SAR) image reconstruction technique to the problem of passive radar imaging. One goal in passive radar imaging is to form images of aircraft using signals transmitted by commercial radio and television stations that are reflected from the objects of interest. This involves reconstructing an image from sparse samples of its Fourier transform. Due to the sparse nature of the aperture, a conventional image formation approach based on direct Fourier transformation results in quite dramatic artifacts in the image, as compared to the case of active SAR imaging. The region-enhanced image formation method we consider is based on an explicit mathematical model of the observation process; hence, information about the nature of the aperture is explicitly taken into account in image formation. Furthermore, this framework allows the incorporation of prior information or constraints about the scene being imaged, which makes it possible to compensate for the limitations of the sparse apertures involved in passive radar imaging. As a result, conventional imaging artifacts, such as sidelobes, can be alleviated. Our experimental results using data based on electromagnetic simulations demonstrate that this is a promising strategy for passive radar imaging, exhibiting significant suppression of artifacts, preservation of imaged object features, and robustness to measurement noise.