A NEW APPROACH TO SPACE DIVERSITY COMBINING IN MICROWAVE DIGITAL RADIO.

A new approach to dual-channel space diversity combining in microwave digital radio is described here. It features (i) adaptive control of the relative amplitudes and phases of the two branch gains; and (ii) a search strategy, based on noncoherent spectrum measurements at the combiner output, that simultaneously accounts for both dispersion and noise. Simulation and analysis programs have been developed to evaluate the scheme for specified pairs of dual-channel responses. Eight representative response pairs are postulated and results are presented for each. They show that the scheme provides a high degree of channel equalization over bandwidths up to at least 40MHz, yielding detection results very close to those of a theoretically optimal combiner. They also show the considerable benefits of the scheme relative to selection diversity and non-diversity operation. Simulation of this scheme over a large ensemble of dual-channel reponse pairs will be necessary to assess its full potential. Early indications are that the scheme would simplify significantly the requirements of follow-on adaptive equalizers, as would be used in long-haul systems with high-level modulations.