Accession Number : ADA127719


Title :   A Geometric Optics Model for Calculating the Field Strength of Electromagnetic Waves in the Presence of a Tropospheric Duct.


Descriptive Note : Final rept. Apr-Dec 77,


Corporate Author : AIR FORCE WRIGHT AERONAUTICAL LABS WRIGHT-PATTERSON AFB OH


Personal Author(s) : Wasky,Raymond P


Full Text : http://www.dtic.mil/get-tr-doc/pdf?AD=ADA127719


Report Date : Dec 1977


Pagination or Media Count : 192


Abstract : The theory and development of a geometric optics model for analyzing the effects of anomalous atmospheric refraction on the field strength of radio frequency emitters is presented. The model is derived from Fermat's principle which defines the Euler-Lagrange equations of a ray and the ray optical path length. This model is applicable to radio propagation above 30MHz where ionosphere effects are generally negligible. Given an isotropic emitter of known frequency, polarization, pulse width, and altitude, the free space normalized power density and field strength are calculated as a function of altitude and distance along the earth's surface. Results obtained with this model are compared to experimental and waveguide mode theory field strength calculations for a low altitude super- refractive atmospheric layer, or tropospheric duct, lying along a 280 nautical mile path off the California coast between San Diego and Gaudalupe Island. Field strength calculations are presented at 65, 170, 520, and 3300 MHz first using the average measured refractive index profile for the Guadalupe Island duct and then a trilinear approximation to that profile. (Author)


Descriptors :   *ELECTROMAGNETIC WAVE PROPAGATION , *TROPOSPHERIC SCATTER COMMUNICATIONS , OPTICS , REFRACTIVE INDEX , GEOMETRY , RAY TRACING , TROPOSPHERE , ATMOSPHERIC REFRACTION


Subject Categories : Radiofrequency Wave Propagation
      Radio Communications


Distribution Statement : APPROVED FOR PUBLIC RELEASE