Multipath Propagation over Snow at Millimeter Wavelengths
A series of multipath measurements over snow were conducted at Hanscom AFB during the winter 1978/1979. Data were obtained over a path-length of 179.5 m at frequencies of 35, 98, and 140 GHz. The gently rolling grass-covered terrain showed maximum height differences of 0.8 m. Snow covers included fr...
| Main Authors: | , |
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| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
1980
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| Online Access: | http://www.dtic.mil/docs/citations/ADA087747 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA087747 |
| Summary: | A series of multipath measurements over snow were conducted at Hanscom AFB during the winter 1978/1979. Data were obtained over a path-length of 179.5 m at frequencies of 35, 98, and 140 GHz. The gently rolling grass-covered terrain showed maximum height differences of 0.8 m. Snow covers included freshly fallen snow, old metamorphic snow, and sleet. The equipment consisted of CW transmitters at 2-m height and receivers mounted on a vertical positioner to measure the height-gain pattern of the received signal between 0.2- and 4-m height. Grazing angles for this geometry range between 0.5 and 2 degrees. Measured interference patterns between direct and terrain-reflected rays were generally coherent in appearance and exhibited cancellation depths of 20 dB and lower, depending on the type of snow cover. A computer program was developed in order to model the reflection as a specular process, with the underlying terrain represented by a series of linear sloping segments, derived from actual terrain height measurements. With appropriate transitions between the linear segments and reflection coefficients calculated from relevant snow parameters, calculated and measured height-gain patterns display quite similar qualities. (Author) |
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