A common control broadband combiner for full frequency band non-regenerative repeating digital microwave radio systems

A common control broadband (CCB) combiner is one of the key devices involved in the development of full frequency band non-regenerative repeating digital microwave radio systems. The CCB combiner must combine two received signals at a frequency bandwidth of 280 MHz. To develop such a combiner, broadband signal transmission characteristics caused by multipath fading are analyzed, a multi-ray model is developed, and propagation parameters for paths over the sea, flat plains and mountainous areas are determined. This paper describes such a combiner. By using the above-mentioned model and parameters, the improvement on fading effected by this combiner with an optimum combining method is calculated and confirmed by experiment. The calculation verifies this combiner can be effectively applied to transmissions over flat plains and mountainous areas. The suitability of the combining method and the calculation method used is also demonstrated experimentally.