Eldon J. Haakinson, Edmond J. Violette, and George A. Hufford

Abstract: A study was conducted to determine the limiting propagation effects on the performance of a microwave system that could be used to detect the optical visibility between two vehicles, separated by up to 10 km, in irregular, obstructed terrain. The study had four objectives: 1) to demonstrate what effects signal variability has on the intervisibility decision process, 2) to identify the possible sources of the signal variability and to estimate the magnitude of each source's contribution to the total variability, 3) to obtain propagation loss data, over various types of terrain and obstructed paths, which could be used to predict received signal variability due to propagation over similar paths, and 4) to use the measured data to predict the performance of a simulated intervisibility measurement system. A measurement system, operating at 9.6 GHz and 28.8 GHz, was prepared and sent to Ft. Hunter Liggett, CA, where propagation path loss was measured over several selected paths of varying lengths, varying path geometries, and varying amounts of vegetation and rock outcroppings. The study shows that a microwave intervisibility system is less perfect than a purely optical one, due to the variability of the received microwave radio signal. However, the performance of the microwave intervisibility system can be predicted based upon the magnitude of the signal's variability. With a limited set of propagation measurements in the area where the microwave intervisibility system is to operate, an estimate of the "optimum" microwave signal threshold and the signal variability can be made; this allows a prediction of the system's performance.

Keywords: intervisibility measurement systems; propagation measurements; SHF

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