| 摘要 |
PURPOSE:To prevent the deterioration in C/N of an output of a voltage controlled oscillator by obtaining a frequency error signal not including noise in a main signal demoluted and multiplied by two. CONSTITUTION:When the circuit is asynchronous, a frequency error signal superimposed with the main signal demodulated and multiplied by two is obtained at an output of a multiplier 4 multiplying an output P signal of an orthogonal phase detector 1 via a delay circuit 3 and an output Q signal of a detector 1. Further, only the main signal demodulated and multiplied by two is obtained at an output of a multiplier 5 multiplying the P and Q signals. Thus, only the frequency error signal is obtained at the output of a substractor 6 subtracting the outputs of the multipliers 4, 5. When the circuit is synchronous, the main signal demodulated and multiplied by two being the same signal is produced at the output of the multipliers 4, 5 as noise, and the noise is cancelled with each other in the output of the subtractor 6. |
