| 摘要 |
PURPOSE:To eliminate a harmonic component of an input completely by providing a filter, a means converting the input into a rectangular wave and a means converting the rectangular wave into a sinusoidal wave to a pre-stage of a demodulation circuit. CONSTITUTION:A limiter 12 receiving an external FSK signal limits an amplitude to a fundamental wave component or below. A BPF 14 passes only frequency components f1, f2 to eliminate the harmonic component. Furthermore, a zero cross comparator 16 converts the result into a square wave. Then an integration circuit 18 integrates an output of the comparator 16 to convert the integrated signal into a triangle wave, it is converted into a sinusoidal wave by a sinusoidal wave. Even when the harmonic component is left after passing through the BPF 14, the zero cross comparator eliminates completely the harmonic component. Furthermore, since the output of the zero cross comparator 16 is converted into a sinusoidal wave by the operation of the integration circuit 18 and the sinusoidal wave circuit, an FSK demodulation circuit 5 receives a substantial FSK signal waveform without harmonic component and noise, in which the signal is accurately demodulated. |
