| 摘要 |
PURPOSE:To detect a pilot signal and a noise individually, by detecting the phase of an input signal by a signal obtained by shifting the phase of the output of the voltage control oscillator of a PLL at 90 deg.. CONSTITUTION:A pilot signal, which is separated from the base band signal by a band pass filter BPF, and a noise near this pilot signal are applied to two phase detectors PD1 and PD2. Signals obtained by shifting the output of a voltage control oscillator VCO for a phase difference of 90 deg. are applied to other inputs of the PD1 and the PD2. The output of the PD2 is fed back to the VCO through a loop filter LPF1 to form a PLL with the pilot signal as a reference. When the pilot signal reaches a certain level or more, the VCO has the phase locked by the pilot signal. Under this state, the DC output of the PD2 is zero, and only noise components are subjected to frequency conversion and are outputted. |
