Evaluation of SAR Performance Degradation in Sparse Random Media: An Analytical Study With 2-D Scatterers

Study of synthetic aperture radar (SAR) resolution degradation in 2-D sparse random medium composed of electrically large dielectric cylinders with possibly high index of refraction is presented. This study is motivated by the need for better understanding of focusing capabilities of SAR systems through random media at submillimeter wave (sub-MMW) frequencies. Analytical recursive expressions are derived to predict the coherence of the transmitted wave as a function of the propagation distance due to different source locations as well as same source location but different operating frequencies. These expressions are directly related to the cross-range and range resolution of the SAR system operating in random media, respectively. Furthermore, by invoking the memory effect property of translational invariant random media, an efficient algorithm is developed to analytically evaluate the coherence functions. The formulations are based on a newly developed coherent wave propagation model, called Statistical S-matrix for wave propagation in spectral domain (SSWaP-SD). A full-wave numerical model in conjunction with Monte Carlo simulations is used to validate the analytical expressions for the coherence. Finally, full wave simulation of a SAR imaging scenario is presented, and a simple method is proposed to reduce the image speckle level without sacrificing the resolution.