Further results of angle and space diversity measurements on a line-of-sight radio link

An experiment conducted to compare angle and space diversity improvement factors over a 51-km path in the east of England has been in progress since early 1988. Angle diversity has been implemented by using two separate parabolic antennas with angular separation between their bore-sights. Narrow-band fading and channel dispersion with three tones are being monitored, and bit error ratios are also being recorded of 6-GHz 140-Mb/s reduced bandwidth QPSK (quadrature phase shift keying) radio systems operating in a cofrequency cross-polar mode. Measurements have been made with a number of angular offsets. The best results to date show that this technique is not as effective as space diversity on this particular hop. Nevertheless, the improvement offered by angle diversity could be of potential use in situations where the full improvement of space diversity is not necessary or it is difficult to use space diversity because of tower loading or lack-of-space considerations