Collimated Beam Wave Pulse Propagation and Scattering in Vegetation Using Scalar Transport Theory

This investigation develops a theoretical model for microwave and mm-wave propagation and scattering in vegetation that is based on radiative transfer theory (transport theory). The time-dependent, three dimensional, scalar radiative transport equation is solved (to a high degree analytically and then numerically) for strong forward scattering of a pulsed collimated beam wave in a strong forward scattering environment such as a forest at mm-wave frequencies. The problem analyzed is that of a periodic sequence of Gaussian pulses incident from free space onto a forest region. The forest is modeled as a half-space of randomly distributed particles that scatter and absorb electromagnetic energy. The incident pulse train is taken to be a collimated (cylindrical) beam wave. The theory allows for a comprehensive characterization of the influence of vegetation on the propagation of pulsed beam waves, which includes a description of the attenuation of these beams, their angular spread, their distortion due to pulse broadening, and the determination of out-of-the-beam scattering which was not previously available. The model should be useful for frequencies above 3 GHz.