| 摘要 |
PURPOSE:To provide a radio wave state discriminating device for cordless telephone which surely discriminates whether an idle channel exists or not regardless of existence of an abnormal noise. CONSTITUTION:The device is arranged in the master machine of cordless telephone, and the output of a second intermediate frequency amplifier 11 is sent to an RSSI part 21, and an RSSI voltage of the reception signal is generated and is sent to a comparator 22 and is compared with a reference voltage, and the high or low level is outputted in accordance with the comparison result and is given to a decision part 23. Meanwhile, the output of an FM detection part 13 is branched and has the noise component taken out by a band pass filter 24, and this noise component is amplified by a noise amplification part 25, and a noise component voltage (noise squelch output) corresponding to the magnitude of the noise is obtained by an AM detection part 26 and is inputted to the decision part 23. The decision part 23 decides that a carrier exists only when the RSSI output is the high level and the noise squelch output is the low level (an abnormal noise exists but a carrier doesn't exist if they are the high level or the low level together). |
