Scatter Model for Pulsed Radio Transmission through Forests

The U. S. Army´s interest in tactical radio communication through media including forests has recently been directed to UHF spread spectrum transmission using very narrow pulses. As the HF c-w models are no longer adequate, a suitable model based on discrete scattering from forest constituents - leaves, branches and trunks is being developed. This paper presents preliminary exercises of this model, which demonstrate some important features, such as partial cancellation of the direct and reflected waves and wide separation between direct and lateral wave responses. Trunks are considered to be long vertical cylinders, branches short ones, and leaves flat circular disks, - all of the same material. Dyadic scattering amplitudes are developed for single scatterers, an effective susceptibility is derived, and an anisotropic slab model is used with an air-forest interface supporting a lateral wave. As the system is linear, the Fast-Fourier Transform is used to provide pulse responses by direct, reflected and lateral waves, which are presented here.