| 摘要 |
PURPOSE:To recover and demodulate a desired carrier wave with almost no adjustment by converting a phase detection output signal into a digital signal and applying digital processing to obtain a phase error signal and a frequency error signal. CONSTITUTION:A quadrant decision section 4 replaces a vector position of a phase detection output signal to a specific quadrant to obtain a digital signal equivalent to the processing that a four-phase modulation signal is multiplied by four times and a nonmodulation signal is formed, and the digital signal is converted into an analog signal by a D/A converter 7 to apply phase control of a voltage-controlled oscillator 2. Further, a quadrant deciding output from the said quadrant deciding section 4 and a quadrant deciding output signal before one sample are compared to obtain an output signal corresponding to the differentiated signal, its output signal is averaged by an averaging section 6 to form an analog signal. Thus, the carrier wave is controlled so as to have the same oscillation frequency as the carrier frequency of an inputted four-phase modulation signal as the control voltage for frequency control of the voltage controlled oscillator 2 to recover the desired carrier wave and to demodulate the 4-phase modulation signal. |
