A Method for Signal Leakage Cancellation in Multistatic Subsurface SAR Imaging System

Multistatic subsurface synthetic aperture radar (SAR) is a promising tool capable of providing 3-D high-resolution images of targets buried underground. The high detection capability of the system stems from the fact that the multistatic configuration allows for viewing the targets from many directions. However, a primal limiting factor for such configuration is the dominance of the direct and ground reflection signals over the scattered target signal hindering the system sensitivity. This letter presents a simple technique to overcome such drawbacks. By an appropriate utilization of SAR data, each adjacent sampling point is coprocessed together as a two-element array in such a way as to have a null along the direction of the direct and ground reflection signals suppressing such signals and making the target signals more discernible. The technique is described in detail, and the potential problems arising from array processing are discussed. Additionally, a modified version of the back-projection (BP) imaging algorithm suitable for the array is provided. The performance of the proposed technique is assessed by simulation data of buried metallic spheres as well as measurement data for a buried metallic pipeline. Both simulation and measurements show a significant improvement in target detection and image quality.