Date of Award

Winter 1995

Project Type

Dissertation

Program or Major

Engineering

Degree Name

Doctor of Philosophy

First Advisor

Kondagunta Sivaprasad

Abstract

A comprehensive system model for characterizing the effects of multipath propagation on digital radio systems in the 4 to 6 GHz band is shown in this thesis. 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 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 field. The channel parameter values are also estimated from these data. Using the channel model, the channel distortions are simulated in the laboratory. The performance of the laboratory test link is characterized to identify the critical parameters for a QAM receiver model. This receiver model is then used to simulate digital signal distortions and a metric is developed for digital signal distortion as a function of multipath interference.

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