| 摘要 |
A frequency demodulator for a frequency shift keyed (FSK) signal which is modulated by two-level digital signals. The demodulator includes a logic circuit and a quadrature detector having a local oscillator frequency which is substantially equal to the center frequency of the received signal to produce a baseband signal in a quadrature phase relationship. The two-level digital signal is recovered as an output of the logic circuits depending upon whether the received FSK signal frequency is higher or lower than the local oscillator frequency. The demodulator solves the problems centered about a need for analog circuits which are undesirable, from an integrated circuit implementation standpoint. The demodulator avoids spike noise which deteriorates the error rate performance which is commonly found in the prior art (e.g. U.S. Pat. No. 4,521,892). |
