Foreground Effects on Troposcatter Digital Communication Systems.
Rept. for Nov 84-Aug 85,
ROME AIR DEVELOPMENT CENTER GRIFFISS AFB NY
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Troposcatter antennas are usually pointed very close to the horizon to maximize system gain. As a result, multipath reflections from the foreground may arise. These multipath signals may have time delays that are significantly longer than direct signals, which are scattered within the common volume and thus degrade system performance. In this report, the effects of terrain-reflected multipath signals on troposcatter digital communication systems are examined. The distance that a ray travels from the transmitting antenna to a point within the common volume is calculated. The maximum differential distance that can occur for a pair of rays that intersect the common volume is than determined for a set of troposcatter geometries. The total distance that a terrain-reflected ray traverses in going from the antenna to the common volume is also calculated. It is found that, for typical troposcatterforeground geometries, the differential distance between a direct ray and a foreground-reflected ray is small compared with the maximum differential distance that exists between direct rays within the common volume. Thus, multipath signals that would have time delays significantly longer than those scattered within the common volume must be scattered from a region outside the common volume.
- Non-Radio Communications