Radar detection in multipath

An analysis of the detection of radar targets in multipath environments is presented. Radar targets often undergo enhancements or fades due to multipath where the direct-path energy combines with a phase-shifted reflection to enhance or reduce the received energy. This phenomenon is a function of frequency. Radars are often designed to avoid the problems of fades by changing frequency or using an assortment of frequencies in an M-out-of-N detector. To understand the detection statistics and choose M and N, the probability density function (PDF) of the noise plus the target times the multipath propagation factor must be known. This PDF is derived for a nonfluctuating target and for a Rayleigh target. The PDF is used to show the benefits of choosing the best M for a multipath environment compared to using the M that would be chosen in a free-space environment