The Existence of a Zero-Cross-Polarization Mode Through Rain

In this paper, it is shown that there exists a zero-cross-polarization mode through rain in which no cross polarization will be induced when orthogonally polarized signals are transmitted. This mode is derived based on a matrix model of the rain-induced depolarization effect for the linear case suggested by Chu [12]. It is also assumed that when the canting angles O of the raindrops are treated as a random variable, the received signal will have an amplitude equal to its expectation value weighted by the probability density of ¿, f (). The zero-cross-polarization mode through rain will then be two orthogonal linear polarizations at an angle ¿away from the conventional vertical and horizontal directions. The magnitude of ¿can be determined if the statistical distribution of the canting angles is partially known. In fact, ¿is determined by only two parameters, ¿and ¿eff, which can be obtained from measured data. It is also shown that whenf (¿) is sysmetric about its mean value, the magnitude of ¿will be exactly that mean value. Some data reported by Chu [12] for ¿and ¿eff provide an example. The results are also extended to the cases of circular polarizations and satellite communications.