Selection Diversity Combiner Design for Digital LOS Radios

The use of an offset threshold performance monitor to control selection diversity combining in a digital Line-of-Sight (LOS) radio is explored. A novel hybrid computer simulation is used to synthesize dual independently fading channels, diversity radio receivers, digital performance monitors and a selection diversity switch. Based on simulations and a theoretical analysis, design relationships for various performance monitor and diversity switch parameters are defined. The optimization of these parameters, such as the response bandwidth of the performance monitor and the switch hysteresis, will maximize the diversity improvement obtainable in a selection diversity system. Finally, a diversity switch algorithm is proposed which integrates outputs from offset threshold and diversity receiver Automatic Gain Control (AGC) monitors to assure effective diversity operation under realistic fading conditions.