DETECTING SYSTEM OF INTERFERENCE WAVE

摘要

PURPOSE:To detect a beat due to interference without errors as an electric signal by using the variation of amplitude at the time of no modulation. CONSTITUTION:A receiving signal (in) is applied to an amplifying circuit 1 which can control gain. The 1st level measuring circuit 2 measures the output level of an amplifying circuit 1 and controls so that the output level of the amplifying circuit 1 is fixed in accordance with the measured result. The 2nd level measuring circuit 2 measures the output (the level of a beat waveform) of the 1st level measuring circuit 2 and applies the measured result to a comparator 4, which compares the measured result with a reference value Vc and detects the level fluctuation of a carrier to apply the detected result to a gate circuit 7. On the other hand, the output of the amplifying circuit 1 is demodulated by a PM (or FM) demodulator 5 and the demodulated output is applied to a call detecting circuit 6. A call detection signal is applied to a gate circuit 7, which is closed during calling. Thus the level fluctuation at calling is prevented from error detection meaning level fluctuation due to interference waves, so that precise detection output (out) can be obtained.