Diversity measurements of attenuation at 37 GHz with sun-tracking radiometers in a 3-site network

The results of a site-diversity experiment at 37 GHz with sun-tracking radiometers at three sites 10.3, 12.7 and 18 km apart, near Slough, UK, are described in relation to Earth-space communication links. Data for observation periods of 16, 8 and 9 months from the three pairs of sites are presented in the form of cumulative distributions and of diversity advantage as a function of attenuation, together with histograms of the number and duration of individual fades exceeding 10 dB. The largest diversity advantage was found for the 18 km spacing and the least advantage was with the 12.7 km spacing for which the sites were aligned approximately perpendicularly to the direction of movement of prevailing storms. A method is given for predicting diversity characteristics at one frequency from measurements made at another, based on two sets of measurements made at Slough; one made concurrently at 19 and 37 GHz, the other made concurrently at 37 and 71 GHz.