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Refractive Effects From VHF to EHF Part A: Propagation Mechanisms.

ADA298694

Publication Date	1995
Personal Author	Hitney, H. V.
Page Count	16
Abstract	Radio wave propagation in the VHF to EHF bands at low elevation angles and near the earth's surface is almost always affected by refraction. This paper details these effects and the various methods used to model them, from simple effective-earth-radius factors for standard refraction to parabolic-equation methods for range-dependent ducting environments. Part A introduces and discusses refraction-related propagation mechanisms and their effects. and Part B describes propagation models and uses examples from propagation assessment systems and other propagation software to illustrate many of the effects. Frequencies from about 30MHz to 100GHz are considered. Refraction and Snell's law are discussed and standard and nonstandard propagation mechanisms are defined. Standard propagation mechanisms are free-space spreading, reflection. forward scatter from rough surfaces, spherical earth divergence, optical interference, diffraction, tropospheric scatter, and absorption. Nonstandard mechanisms discussed are evaporation ducts, surface-based ducts from elevated trapping layers. elevated ducts, lateral inhomogeneity, and terrain effects. To establish the significance of nonstandard propagation effects, some statistics on the occurrence of ducting around the world are presented. Specifically. statistics on the strength of evaporation ducts for selected areas and on the frequency of occurrence of surface-based ducts are presented. (MM).
Keywords	Refraction Radio transmission Radio waves Atmospheric refraction Computer programs Nato Refractive index Surface roughness Atmospheric scattering Terrain Wave propagation Absorption Earth surface Evaporation Elevation Ray tracing Decision aids Troposphere Radiofrequency interference Extremely high frequency Transmission loss Very high frequency Radar navigation Radio navigation Forward scattering Snells law Reprints Nato furnished
Source Agency	Non Paid Reprints
NTIS Subject Category	46H - Radiofrequency Waves 45C - Common Carrier & Satellite 55A - Aeronomy 48C - Natural Resource Surveys
Corporate Authors	Naval Command, Control and Ocean Surveillance Center, San Diego, CA. RDT and E Div.
Document Type	Journal Article
Title Note	Professional paper.
NTIS Issue Number	199605

Refractive Effects From VHF to EHF Part A: Propagation Mechanisms.

Refractive Effects From VHF to EHF Part A: Propagation Mechanisms.
ADA298694

Publication Date	1995
Personal Author	Hitney, H. V.
Page Count	16
Abstract	Radio wave propagation in the VHF to EHF bands at low elevation angles and near the earth's surface is almost always affected by refraction. This paper details these effects and the various methods used to model them, from simple effective-earth-radius factors for standard refraction to parabolic-equation methods for range-dependent ducting environments. Part A introduces and discusses refraction-related propagation mechanisms and their effects. and Part B describes propagation models and uses examples from propagation assessment systems and other propagation software to illustrate many of the effects. Frequencies from about 30MHz to 100GHz are considered. Refraction and Snell's law are discussed and standard and nonstandard propagation mechanisms are defined. Standard propagation mechanisms are free-space spreading, reflection. forward scatter from rough surfaces, spherical earth divergence, optical interference, diffraction, tropospheric scatter, and absorption. Nonstandard mechanisms discussed are evaporation ducts, surface-based ducts from elevated trapping layers. elevated ducts, lateral inhomogeneity, and terrain effects. To establish the significance of nonstandard propagation effects, some statistics on the occurrence of ducting around the world are presented. Specifically. statistics on the strength of evaporation ducts for selected areas and on the frequency of occurrence of surface-based ducts are presented. (MM).
Keywords	Refraction Radio transmission Radio waves Atmospheric refraction Computer programs Nato Refractive index Surface roughness Atmospheric scattering Terrain Wave propagation Absorption Earth surface Evaporation Elevation Ray tracing Decision aids Troposphere Radiofrequency interference Extremely high frequency Transmission loss Very high frequency Radar navigation Radio navigation Forward scattering Snells law Reprints Nato furnished
Source Agency	Non Paid Reprints
NTIS Subject Category	46H - Radiofrequency Waves 45C - Common Carrier & Satellite 55A - Aeronomy 48C - Natural Resource Surveys
Corporate Authors	Naval Command, Control and Ocean Surveillance Center, San Diego, CA. RDT and E Div.
Document Type	Journal Article
Title Note	Professional paper.
NTIS Issue Number	199605