A new combiner for multi-antenna diversity in multi-carrier microwave radio systems

A novel combiner for multiantenna diversity in a multicarrier digital microwave radio is described. To improve the control accuracy and dynamic response to fading, an individual in-phase space diversity (SD) combine method and a digitally controlled phase detecting method is proposed. The required phase control speed becomes about 1000°/sec assuming a two-ray fading model, and the proposed combiner can follow such a high-speed fading. The circuit can also be made up of LSIs. In a field examination of 256QAM (quadrature amplitude modulation) transmission, an individual in-phase SD was evaluated and showed remarkable improvement in reducing outages caused by multipath fading