Selectively Faded Nondiversity and Space Diversity Narrowband Microwave Radio Channels

The spectral characteristics of nondiversity and space diversity narrowband radio channels subject to multipath fading were estimated from a detailed sampling of channel loss variations as measured on two vertically separated antennas. The data base for this analysis was obtained during a 93-day experiment in which the amplitudes of a set of coherent tones spanning a band of 33.55 MHz and centered at 6034.2 MHz were continuously monitored. The most significant observations were: (i) For the nondiversity channel, the frequency selectivity of the received transmission loss generally exceeded linear and quadratic components (in frequency) of amplitude distortion for fade depths greater than 30 dB. (ii) For the diversity channel constructed by switching between a pair of narrowband channels received on two vertically spaced antennas, the frequency selectivity of the transmission loss was significantly reduced.