Effect of Rain on Millimeter-Wave Propagation-A Review

摘要

Rain severely affects the propagation of electromagnetic waves above 10 GHz. Attenuation and depolarization of signals are caused by the presence of the rain drops. Rain attenuation depends in a complex manner, on the dropsize distributions, temperature and terminal velocity of rain drops, vertical and horizontal structure of the rain cell, wave length of the signal etc. depolarization depends on the non-spherocity of the rain drops.In this Review, the subject has been introduced in Section 1. In Section 2, the theory of rain attenuation has been described. Various dropsize distributions which depend on the point rain rate, on the basis of rain measurements are given in this section. In order to describe the behaviour and effects of the rain completely statistical models have been developed which are described in Section 3 on the basis of world wide measurements. This Section includes the statistical cumulative distribution of rain fall rate, rain attenuation models for terrestrial and earth-space paths, frequency and path length scaling, worst month statistics and cross-polarization statistics. Comparison between various statistical models is given in Section 4. In Section 5 we have discussed the applicability of various statistical models for different geographical regions described on the basis of extensive measurements.