Análise da propagação troposférica sobre terrenos irregulares em VHF e UHF utilizando equações parabólicas e o desenvolvimento de um novo modelo híbrido para predição de perda de percurso

Abstract

This work performs a general analysis on the propagation of electromagnetic waves through the troposphere over irregular terrain in the VHF and UHF bands. This is the main scenario of the so-called terrestrial waves, which comprise most of the widespread telecommunications services in society. The analysis begins with concepts of electromagnetics, passes through important aspects of antennas and covers most mechanisms that affects this type of propagation, such as: free-space propagation, propagation over flat and spherical Earth, Tropospheric propagation, diffraction over obstacles and propagation over irregular terrain. In addition, the parabolic equation method is developed in detail for propagation in this scenario and a number of tests and comparisons are performed to prove its operation. However, this method is intricate to implement in order to consider all aspects of propagation like the irregular terrain, for example. Therefore, a new hybrid propagation model is developed aiming to take advantage of an easier part of the parabolic equation model and combining it with the simple Bullington knife-edge diffraction model. In this case, the effects of terrain irregularities are considered explicitly. Results demonstrate the great potential of the developed model and its superiority compared to well known models such as the Recommendation of ITU-R P. 1546.