Forward Scatter Shadow Ratio: Concept and Its Application in Shadow Profile Retrieval

Traditionally, the radar cross-section is used to characterize the target in a forward scatter radar (FSR) system, the measurement of which requires the availability of the scattered signal. However, the scattered signal is often hard to be extracted, particularly when the illumination signal is opportunistic. In this paper, we introduce the concept of the forward scatter shadow ratio (FSSR) of a target as the ratio of the total received power density to the incident power density for a receiver at a certain location in an FSR system. It is argued that the FSSR can be a useful parameter in the studies of FSR systems as it is relevant to target detection, size estimation, classification and shadow profile imaging. Particularly, using mathematical analysis and numerical results, we demonstrate that the shadow profile of a target can be retrieved with the FSSR. The three sources of error in shadow profile retrieval, i.e., uncentered line of observation, shadow profile discretization and approximation of the imaginary error function are discussed.