Multipath Propagation over Snow at Millimeter Wavelengths

• Main Authors: Lammers,Uve H W, Hayes,Dallas T
• Other Authors: ROME AIR DEVELOPMENT CENTER GRIFFISS AFB NY
• Format: Text
• Language: English
• Published: 1980
• Subjects: Snow; Ice and Permafrost; Computer Programming and Software; Radiofrequency Wave Propagation; *SNOW COVER; *MULTIPATH TRANSMISSION; *RADIATION PATTERNS; *INTERFERENCE ANALYZERS; COMPUTER PROGRAMS; CONTINUOUS WAVES; MILLIMETER WAVES; RECEIVERS; TRANSMITTERS; EXTREMELY HIGH FREQUENCY; KA BAND; LOW ANGLES; SPECULAR REFLECTION; GRAZING; Height gain patterns; Metamorphic snow; Terrain reflected rays; Grass covered terrain; Terrain height; M Band; Grazing angles; PE62702F; WURADC46001607; Ice; permafrost
• Online Access: http://www.dtic.mil/docs/citations/ADA087747; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA087747

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)