Space Correlations of 35‐GHz Transmissions Over a 28‐km Path

Abstract

Experiments have been carried out in order to measure the spatial and temporal nature of amplitude fluctuations observed on a 35 GHz, 28‐km line‐of‐sight transmission path. The fluctuations are typically 1 dB in amplitude, with spectral widths of up to 1 Hz, and apparently drift horizontally past the several receiving antennas. The velocity of this drift, as determined by cross‐correlation analysis of the fluctuations at several points, correlates well with the spectral width of the fluctuations, and is also correlated with observed windspeeds, indicating that the observed drift of the amplitude fluctuations is the result of the gross motions of the atmosphere. No corresponding drift was observed for vertical antenna separation. The spatial scale length of the fluctuations remained approximately the same for all conditions encountered, in both the horizontal and vertical planes. It is concluded that the temporal characteristics of the received signal are largely the result of the horizontal drift of a relatively fixed spatial distribution of amplitude, rather than of temporal changes in this distribution.