| 摘要 |
PURPOSE:To improve linearity of demodulation to facilitate amplitude (sound volume) control, by inputting the frequency-modulated signal and by varying the pulse width of the means, which generates pulses with the repeat corresponding to this input, by the control signal. CONSTITUTION:The sound intermediate frequency signal subjected to FM modulation from input terminal 1 is converted to a pulse signal of pulse width modulation by operational amplifier 7, and monostable multivibrator circuit 8 is triggerred by the rise of this pulse and generates the pulse of a certain pulse width. This pulse width is changed by control power source 85. Thus, low-band components (sound signal) after passage through filter 9 have the amplitude changed by change of the pulse width. Consequently, the sound volume control circuit is unnecessary after filter 9, and it is sufficient if power amplifier 5 and speaker 6 are connected. |
