| 摘要 |
PURPOSE:To ensure the correct discrimination whether the initial tracking is in lockin state or not, by giving a shift of a certain value between the initial phase values during the start of tracking of the 1st and 2nd phase tracking circuits which receive the input signal and track the phase. CONSTITUTION:An initial phase setting circuit 4 sets the 1st and 2nd phase tracking circuits 2 and 3 at the initial phases and 0 respectively when a power supply is applied or the tracking of phase is started. Accordingly the output of a phase difference calculating circuit 5 is set as ¦thetaI-thetaII¦=¦pi-0¦=pi. When the circuits 2 and 3 start the tracking to the signal (phase thetas) which is applied to a signal input terminal 1, both thetaI and thetaII get gradually close to thetas. Accordingly the output of the circuit 5 becomes gradually close to 0 from pi to be set at 0 when thetaI=thetaII=thetas is satisfied. As a result, the initial phase lock-in state can be decided for the phase tracking system by monitoring the level of the output emerging at a phase lock-in signal output terminal 6. |
