Use of zero-forcing equalization for space diversity combining in microwave digital radio

One of the primary causes of performance degradation in microwave digital radio is frequency selective fading caused by multipath propagation. For an M-QAM radio system, dual space diversity and adaptive zero-forcing equalization countermeasures can be employed in two configurations. In an optimal-selection diversity structure, after equalization of the two diversity channels, the better one is selected while in a post-combining equalization structure the channels are combined prior to equalization. By analytic techniques and Monte Carlo simulation we determine that for the same transmit power the improvement attained is greater with the post-combining equalization structure. Also, we show that the seven tap post-combining equalization structure can outperform the conventional optimal selection-diversity structure even when infinite taps are used.