Numerical simulations of propagation over a time varying ocean surface

Analysis of forward scattering of electromagnetic waves by random rough surfaces is of interest in maritime communications. The effects of the time varying behavior of the ocean on propagation have not yet been explored with more realistic models. In this paper, the characteristics of the received power are investigated using one-dimensional realizations of a Pierson-Moskowita ocean surface which evolve according to a gravity wave dispersion relation, as described in Rino et al. (1991). The ocean surface is assumed to be a perfect electric conductor, at an operating frequency of 1 GHz. Atmospheric effects such as ducting and scintillations are neglected for simplicity. Simulations of scattering are performed using a windowed fast multipole method (Ungan and Johnson 1997) to speed up the method of moments solution. In the following, numerical simulation results are presented and compared for both stationary and linearly propagating ocean surface realizations, and coherent and incoherent components of the received signal are examined under both ensemble and time averages. Moreover, the spectrum of the total field reaching the receiving antenna is analyzed to investigate the frequency offset introduced due to the rough ocean surface.