| 摘要 |
PURPOSE:To prevent the malfunction dependent upon an adjacent disturbing wave in a simple constitution by detecting DC components of frequency discriminator and discriminating whether they are the disturbing wave or not. CONSTITUTION:Receiving signals are subjected to frequency conversion by mixer 3 through HPF 2 and are subjected to IF amplification in 7, and after that, they are subjected to amplitude limiting by limiter 8 and are outputted. In this case, the output of amplifier 7 is detected by 18, and the output is amplified by DC amplifier 16-1; and meanwhile, the output of IF filter 9 is subjected to frequency discrimination in 12 and is led to LPF 19 and has only DC components taken out, and the DC components are subjected to DC amplification by amplifier 16-2. These outputs are inputted to logical operation circuit 20 to drive relay 17 by any of these signals. Then, as regards the output of LPF 19, OV or approximately OV for a desired signal wave and an output proportional to the frequency difference between an adjacent disturbing wave and the desired signal wave for the needless signal wave which is an adjacent disturbing wave are obtained. As a result, the malfunction dependent upon the adjacent disturbing wave can be prevented in a simple constitution. |
