OVERWATER LINE-OF-SIGHT FADE MEASUREMENTS AT 37 GZH

The short-term fading on an overwater line-of-sight path at 37 GHz was characterized. Fade depths of 8 db were typical, although fade depths from 3 db to 14 db were observed (measured between the median and the 98% value of the distribution). The fading generally displayed a fast and a slow component with typical average values of about 0.5 fade per second and 1.5 fades per minute. The corresponding average fade durations were 1 sec and 20 sec, respectively. The importance of the specular reflection from the water surface was clearly evident in the results. The typical value of the specular reflection coefficient was about 0.7, but the extreme values varied from almost 0 to 1. The reflection coefficient of the diffusely scattered component showed less variation and was typically about 0.25. The use of a 15-db fade margin would be sufficient to maintain the received signal above a desired threshold for at least 98% of the time for every sample of data examined. For effective time diversity operation, a time delay of about 10 sec would likewise be sufficient for every sample examined. (Author)