The 11.9-GHz rain attenuation and site diversity effect on the earth-space paths of low elevation angles

In order to study rain attenuation characteristics and site diversity effects on earth-space paths of elevation angles lower than 10°, sky noise measurements by radiometers at 11.9 GHz and 1-min rain rate observation were conducted with several site diversity configurations in the western part of Japan. Measured statistics such as the cumulative distributions of 11.9-GHz single-site rain attenuation and related joint probabilities at diversity sites are presented. It is shown that extensively spread rain regions associated with typhoons or frontal lines have considerable effect on both rain attenuation and site diversity distributions. As a guide to prediction of site diversity effects for low elevation angle conditions, joint probability of rain attenuation as a function of site spacing from 17 to about 200 km is derived from the measurement results. Also shown is the site diversity effect dependence on elevation angle.