Very high frequency radiowave scattering by a disturbed sea surface Part I: Scattering from a slightly disturbed boundary

Abstract

This paper considers the scattering of very high frequency (VHF) electromagnetic waves from a random weakly corrugated surface by the perturbation method. The calculations show that the scattering has a resonant nature, i.e., only certain Fourier components of the surface shape are responsible for scattering in every given direction. Experiments carried out in a water basin confirmed the results of the calculations. The backscattered intensity is proportional to the spectral density of those Fourier components of the surface oscillation that have a resonant space period. In these experiments, resonant maxima of the reflected signal corresponding to the second-order approximation of the perturbation method were also observed. The frequency spectrum of the scattered electromagnetic field is also investigated. It is shown that the spectrum of the scattered radiation is shifted from the incident frequency by a certain value related to the phase velocity of the resonantly scattering Fourier component of the surface shape. The experimentally observed dependence of the scattered intensity on frequency and the theoretically predicted one are very much alike.