Prediction and measurement of the coherent and incoherent power reflected from a rough surface

A theoretical treatment based on the concept of statistical sampling shows that the signal received in the specular direction when a plane wave is incident obliquely on a rough surface can be considered as the vector sum of a constant signal and a random signal. The random signal consists of two components, which are approximately normally distributed and independent, one in phase with the constant signal and the other in phase quadrature. Except for very rough surfaces the variances of the two random components are not equal, the variance of the phase quadrature component being greater than that of the in-phase component. The theoretical results are shown to agree with those based on other theoretical approaches and are in addition confirmed by experiments using microwaves reflected from a calibrated rough-water surface.