| 摘要 |
In a digital mobile communication system wherein one communication channel is used by a plurality of system users by time sharing, the communication channel being used in a certain zone is switched to a predetermined other communication channel when the user moves from the communication zone to another neighboring zone, and RSSI levels of the predetermined communication channels in the neighboring zones are monitored by using an empty slot of the communication channel preparing for the channel switching during the communication of the user in the channel, a monitor circuit for the RSSI level of the system includes two band pass filters having a narrow frequency band width and a wide frequency band width connected in parallel with a switch that activates only one of them. In the receiving slot, the filter having a narrow frequency band width is used and in the empty slot, the frequency of the first local oscillator is changed to the monitor channel and the filter having a wide frequency band width is used, so that the RSSI level can be detected within the empty slot.
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