| 摘要 |
PURPOSE:To output a pseudo locking detection signal by applying synchronous detection to a signal with a frequency component appearing at the output of a multiplier multiplying the multiplication output of Ich and the multiplication output of Qch of a COSTAS loop type demodulator demodulating a phase- modulated carrier at the pseudo lock of the COSTAS loop type demodulator. CONSTITUTION:When a COSTAS loop type demodulator 20 is locked normally, since the level of an output signal S8 of a multiplier 25 of the COSTAS loop type demodulator 20 is nearly zero, the value of the detected signal S10 is nearly zero. On the other hand, when the carrier frequency of an input modulation signal S5 is shifted by the integer multiple of the bit rate of the data transmission in the increasing direction more than the oscillated frequency of a VCO 27 of the COSTAS loop type demodulator 20 and the pseudo lock state takes place, the level of the detected signal S10 reaches a prescribed level TH or above. Thus, the pseudo locking state of the COSTAS loop type demodulator is detected. |
