Análise da propagação de ondas eletromagnéticas em canais com desvanecimento

Abstract

A very important problem in radio communication systems is the fluctuation in received signal level, caused by several factors that affect the electromagnetic waves propagation. The phenomenon is called fading and among it’s most important causes one can mention the received signal combination from multipath between the transmitter and the receiver, changes at the environment propagation characteristics, and so on. Frequently, the compound signal at the reception antenna results in combinations that does not obey a predictable law, once the responsible factors over the link depend on propagation conditions, associated to meteorological and environmental effects. To create a reliable system project and installation it is necessary the exact knowledge of several mechanisms which degrade the signal, aiming to provide some ways to compensate them. In this study, it will be analyzed the signal behavior in an environment that helps this effect to appear. It will be discussed the statistical distributions that can estimate the random signal fluctuation. Laboratory simulations will be realized to certify the link behavior under fading presence. The detrimental effects of the system quality with digital modulation are emphasized.