| 摘要 |
PURPOSE:To detect accurate radio wave interference by adding an amplitude fluctuation component to a signal being the result of squaring an FM modulation signal and detecting the amplitude fluctuation component of the addition output so as to eliminate an error due to the signal component by FM-AM conversion. CONSTITUTION:An output from an antenna 10 is fed to a frequency conversion circuit 14, where the signal is converted into an intermediate frequency signal, which is fed to a limiter amplifier 18 and a logarithmic detector 20. Then the intermediate frequency signal subject to amplitude limit by the limiter amplifier 18 is fed to an FM demodulator 22 to apply FM modulation. A demodulated output signal of the FM demodulator 22 is fed to a square circuit 26, where the signal is squared, and the output of the square circuit 26 and the output signal of the logarithmic detector 20 are fed to an adder circuit 24, where they are added. The added output of the circuit 24 is fed to a level detector 30 via a high pass filter 28 to detect the output of the high pass filter 28. Thus, the amplitude fluctuation component caused by the FM-AM conversion is eliminated to obtain the radio wave interference accurately. |
