| 摘要 |
PURPOSE:To improve the S/N by constituting the titled circuit by an envelope detector extracting a detection output from a common emitter connecting an envelope detection capacitor and a waveform shaping device waveform-shaping the output of the detector. CONSTITUTION:An amplitude modulation wave superimposed with a noise component N1 on one base and only the noise component N2 is inputted to the remaining base and when a control signal is an amplitude modulation wave corresponding to 0, the input noise is subject to envelope detection by a diode and a capacitor C1 between the base and emitter of transistors(TRs) Q1, Q2, added at the emitter simultaneously and the noise component (N1+N2) is extracted. When the control signal is an amplitude modulation wave corresponding to 1, however, the modulation wave is subject to envelope detection by the diode and the noise component N2 entering the remaining base is shut off because the diode is reverse-biased and not outputted to the emitter. Thus, in case of the amplitude modulation wave where the control signal is 1, the noise component N1 inputted to the other base is not added and the S/N of demodulation signal is improved. |
