| 摘要 |
PURPOSE:To improve the demodulation stability by providing a 1st demodulation circuit section demodulating an FSK signal based on a modulation signal with a higher frequency and a 2nd demodulation circuit section demodulating an FSK signal based on a modulation signal with a lower frequency to the demodulator. CONSTITUTION:A modulation wave whose frequencies are modulated as fo+f and fo-f is sent from an intermediate frequency amplifier 1 to a 1st demodulation circuit section 6 and a 2nd demodulation circuit section 7, in which the wave is fed respectively to respective FM detection sections 6a, 7a. Then the detector 6a sends a detection signal of a voltage Vo+V when the frequency is fo+f and sends a detection signal of a voltage Vo when the frequency is fo-f. The signal is sent to a comparator section 6c via an LPF 6b. In this case, a voltage change in the sent detection signal is V(=(Vo+ V)-Vo), resulting in being decreased. Moreover, the detector 7a sends a detection signal of a voltage Vo when the frequency is fo+f and sends a detection signal of a voltage Vo-V when the frequency is fo-f. Thus, a very stable digital signal is sent from a comparator section 7c to a data decoder 8 similarly to the case above. |
