Optimal frequencies and polarizations for radar detection of targets

SAR radars create 2D maps of terrain. Each image pixel corresponding uniquely to a terrain resolution cell. Due to terrain inhomogeneity and SAR's inadequate resolution, some of the resolution cells may contain multiple elementary scatterers belonging to different classes. Radar returns from such a resolution cell are attributable to collective interaction of electromagnetic waves which are scattered by various kinds of elementary scatterers within the resolution cell. Simultaneous use of multispectral and polarimetric measurements at the pixel makes it possible to decorrelate signals from different classes of elementary scatterers within the corresponding resolution cell, facilitating the separation of different subpixel-sized elementary scatterers in each pixel. Frequency and polarization diversity offered by multifrequency and polarimetric SAR provides a method to tackle an important yet challenge task: detecting stationary manmade ground subpixel-sized targets from complex natural clutter. The objective of this investigation is to optimize frequencies and polarizations for detecting subpixel-sized target in clutter using multilook, multifrequency polarimetric SAR data for a pixel. In the general target-plus-clutter versus clutter case, a general target detection model is established first. Then, based on this model, typical polarimetric covariance matrix parameters at several bands are used to illustrate the procedures of optimizing frequencies and polarizations for small target detection in clutter.