A Geometric Optics Model for Calculating the Field Strength of Electromagnetic Waves in the Presence of a Tropospheric Duct.
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)
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1977
- Accession Number
- ADA127719
Entities
People
- Raymond P. Wasky
Organizations
- Wright Laboratory