Calculation of the allan variances for the rain‐attenuated millimeter wave beacon from a geostationary satellite, and their application to the site‐diversity switching

Abstract

AbstractWe calculated the Allan variance (the frequency stability measure in the time domain) of a rain‐attenuated 34.5 GHz beacon signal transmitted from a geostationary satellite. the obtained results showed that the rain‐attenuated signals basically had random‐process characteristics with fα (α < 0) types of power spectral densities‐typically with α = ‐2, i.e., a random walk process. Also calculated were the Allan variances of bit error rates (BER's) of time division multiple access (TDMA) signals which were attenuated by rain. Occasionally, the measurements showed that the variances were reduced to only a few seconds. We applied these results to sitediversity switching experiments and tried to determine optimum times to measure and compare the BER's of the TDMA signals to be switched (they came from both routes of the main and substations). Simulation experiment results showed that the measuring times to minimize the variances coincided almost with those to minimize switching errors. This was also proved by theoretical analysis.