| 摘要 |
PURPOSE:To attain the phase detection at the straight line part of the transmission characteristic at all times by blocking the phase difference between an input signal and a reference frequency signal from reaching the singular region of the transmission characteristic of a phase detector. CONSTITUTION:A DC component detection means 120 detects a DC component of the output signal POUT of the phase detector 110 and generates a DC detection signal VD in response to the level. When the DC detection signal level inputted from the DC component detection means 120 exceeds a prescribed threshold level, a phase control means 130 changes the relative phase difference between the reference frequency signal and the input signal by a prescribed quantity thereby detecting the phase at the linear operaton characteristic region of the transmission characteristic of the phase detector 110. The threshold level is selected to a value in the vicinity and not exceeding the upper and lower limits of the DC detection signal outputted from, e.g., the DC component detection means 120. |
