Rain-induced crosspolarisation on line-of-sight systems at 38 GHz

Factors affecting rain-induced depolarisation at 38 GHz have been investigated. The effect of raindrop canting on the crosspolar signal levels has been examined together with other, more minor, factors such as water temperature and drop shape model. The intervening medium between the two terminals is assumed to have constant rainfall rate and the crosspolar effects are evaluated for various link separations and for various rain intensities. Additionally, data obtained from the Chilbolton radar are used and the depolarisation effects due to typical precipitation events are assessed. Results indicate that, for a standard 38 GHz PCN (personal communication network) system, the use of linear, orthogonal polarisations is not likely to present operational problems. Compared with the copolar fading of the wanted signal and the depolarisation introduced by antennas typically used by the operators, the effects of rain-induced crosspolarisation are shown to be almost negligible