The effects of wet radome on a short millimetre-wave link in Singapore

A short line-of-sight link has been set up at the Nanyang Technological University (NTU) in Singapore to monitor the effect of rain on microwave link performance at 38 GHz. The results suggest that the rain attenuations derived from the measured received levels are much greater than those computed using the ITU-R models. Other studies at the School of EEE, using raindrop size distribution data collected at NTU, indicate that although the rain specific attenuations are higher, they are not as high as the measured value assuming that rain attenuation was the main attenuation mechanism. The effects of water on the antenna radome is a possible cause of the higher attenuation measured. Tests were conducted to evaluate the effects of water on the antenna radome. These results suggest that significant losses could be introduced at a higher microwave band like 38 GHz. Two techniques, called the correlation and equiprobability methods, were developed to separate the attenuation due to rain along the path and that due to water on the antenna radome. The relationship between wet radome loss and rainfall rate in true rain events is also shown for the 38 GHz radio link