Space wave field produced by a vertical electric dipole above a perfectly conducting sinusoidal ocean surface

Investigations of electromagnetic scattering from rough surfaces have been oriented toward radar surveillance or remote sensing applications. An important problem that has been relatively unexplored is that of a dipole antenna close to and illuminating an ocean surface with spherical waves; for example, communication antennas on submarines or surface ships. This work is concerned primarily with the fluctuations in the space wave field intensity caused by reinforcement and cancellation of the direct wave by the wave reflected from a moving sinusoidal ocean surface. Certain situations arise so that the sinusoidal model is a good approximation of an actual ocean surface. For this case, the amplitude of the sine curve is small compared with a free-space wavelength; therefore, a Fourier integral-perturbation series approach can be used to solve the boundary value problem. Two primary conclusions are drawn from this model of the ocean surface. First, the widest field variation occurs in the direction broadside to the direction of wave motion. Second, a depolarized field term is introduced, and it is directly proportional to the maximum slope of the surface. Finally some practical aspects of RF communications are discussed. For example, it is noted that the RF fading rate is related to sea state.