| 摘要 |
A radio relay method for digital communication using a heterodyne relay system consisting of terminal stations and relay stations each having radio repeaters using radio frequency of microwave or millimeter wave. The radio repeater usually receives a desired signal as a correct signal for a route to which the terminal and relay stations belong, however, the radio repeater can receive an undesired signal, whose level is beyond the threshold level of a squelch circuit in the radio repeater, produced by interference with an radio signal from an adjacent different route for example. When the desired signal decays due to fading for example and the undesired wave becomes dominant, the terminal station of the route must distinguish which relay station has a trouble. The radio repeater of the present invention detects a received route signal from the received undesired signal; determines whether the received route signal is incorrect for the route, stops a received main signal in the received undesired signal, and sends only a supervisory signal to successive relay stations with a correct route signal generated by the radio repeater, so that the terminal station can detect the route signal and recognize the state of the relay station from the supervisory signal.
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