Propagation Tests for 23 GHz and 40 GHz

Propagation tests were conducted on the 23 GHz and 40 GHz bands on the same 1.08 km path in Nagoya City, Japan, for two years (1979 and 1980), in order to collect circuit design data for a highly reliable millimeter wave intracity communication link. The path attenuation versus 1 min rain rate relation for the same cumulative percentage of time was obtained and compared to the theoretical curves of various raindrop distributions such as Laws and Parsons. We found some discrepancies on both the high rain rates, exceeding 50 mm/h, and low rain rates. The former was thought to be due to a mismatch between the rain gauge integration time and the path attenuation time constant. From the coincidence of the autocorrelation functions of both the rain rate and path attenuation, we were able to determine the best fit integration time. The latter was due to the loss of the radome in the rain. The circuit outage of the short path millimeter wave radio link was strongly affected by the heavy rains which exceeded 60 or 100 mm/h in thunderstorms, fronts, and typhoons, and was characterized by bursts of rain. Based on the 1 min rain rate records for five years, 1975-1979, we found the heavy rain statistics obeyed Poisson's distribution. Finally, we introduced a propagation test of 40 GHz through fire flames and found the losses to be low.