On the scattering of electromagnetic waves by a moving tropospheric layer having sinusoidal boundaries

The trans-horizon signal is assumed to be adequately described by a simple Waterman scatter model and to be ascribable to a partial reflection from a "rippled atmospheric layer." Here it is assumed that the boundary of this layer is space sinusoidal in a plane normal to the line determined by the transmitter and receiver points. The thickness of the layer is approximately uniform and the permittivity is assumed to vary in a Gaussian manner. Theoretical and experimental descriptions of the vertical-transverse permittivity spectrum are obtained and compared. A corresponding comparison is made between the theoretical and Waterman experimental received power vs azimuth angle patterns. In both cases, there is qualitative agreement provided the ratio of ripple amplitude to ripple wavelength is large. In addition, an estimate of the trans-horizon signal power spectrum is compared with experimental observations. Experimentally, the power spectrum is found to broaden with increasing scattering angle and beamwidth, while the present scatter model yields a power spectrum whose width is an inverse function of scattering angle and beamwidth.