Coherent non-regenerative repeater digital microwave radio system field test

The first field test results of a coherent nonregenerative repeater digital microwave radio (CNR-DMR) system are presented. Among the cumulative degradation factors in fading state on nonregenerative repeating, self interference caused by passing adjacent channels (S-IPAC) and cross polarization interference are the main factors. The S-IPAC becomes intersymbol interference and cumulative cross polarization interference is changed to diverse multipath interference, since a coherent relationship between transmitter and receiver devices or between vertical and horizontal devices is maintained constant. These interference signals can be easily removed by equipping the terminal station with a decision feedback equalizer and a transversal filter type diverse cross polarization interference canceller. From the compensating effect obtained in the field test by using two nonregenerative repeaters with the equalizer and the canceller, it is clarified that the transmission quality of the CNR-DMR system is just as high as that of a regenerative repeater system