| 摘要 |
PURPOSE:To simplify the titled circuit by providing a means injecting a low frequency signal to a phase locked loop through a low pass filter and a means introducing an output of a voltage controlled oscillator to extract the said low frequency signal and the deciding extracted signal level so as to detect the phase locking. CONSTITUTION:A phase comparator 1, an LPF 2 and a voltage controlled oscillator 3 constitute a phase locked loop type angular demodulator. An output of a low frequency oscillator 11 is inserted to a phase locked loop from the LPF 2. An output of the oscillator 3 is inputted to a frequency discriminator 12 and its output is inputted to a level detection discriminator 14 via an LPF 13. A low frequency is injected to the phase locked loop so as to act itself like a kind of external signal and the output of the oscillator 3 is subject to frequency discrimination so as to extract the said low frequency signal in this way and the level is decided by a level detection decides 14 to monitor the phase locked state. |
