A channel model for multipath interference on terrestrial line-of-sight digital radio

A comprehensive system model for characterizing the effects of multipath propagation on digital radio systems in the 4-6-GHz band is shown in this paper. The effects of terrain-induced multipath propagation in the presence of atmospheric anomalies are studied using data from experimental microwave links in the field and in the laboratory. This technique, which treats multipath propagation as digital signal distortions caused by interference from ground reflections, has not been shown previously. A forward multipath propagation model is used to identify the critical propagation parameters for a quadrature amplitude modulated (QAM) signal. A normalized two-ray channel model is developed to approximate the frequency response produced by interference from a ground reflection in a narrow band. The effectiveness of this channel model is evaluated using measured data from the test radio link in the laboratory and in the field.