Solução numérica e assintótica de propagadores para a faixa de HF

Abstract

For many years, integral equation models have been developed to characterize propagation of radio wave over smoothly varying and inhomogeneous terrain whose profile varies continuously in the propagation plane. The work proposes the study and application of an integral equation that determines the attenuation function on a Gaussian profile in the high-frequency band (3 MHz a 30 MHz). The computer program used to estimate the attenuation function in HF band is based on the formulation of this integral equation for the field over smoothly varying and inhomogeneous terrain, using the free-space Greens function in Greens second identity, which is related to flat earth attenuation function in the HF band. The program becomes numerically unstable for frequencies above 10 MHz. In order to validate the efficiency of the algorithm in the HF band, the results were compared with the values of the recommendation ITU-R P.368-9. Finally, the numerical analysis is extended to a generical surface through the numerical method of interpolation cubic spline. The study analyzes the integral equation in five profiles located in Denmark.