| 摘要 |
PURPOSE:To reduce the data jitter while extending the lead-in range of the frequency by comparing the phase to ensure locking to the same phase after detecting the coincidence through a comparison between the input frequency and the self oscillation frequency. CONSTITUTION:Voltage control oscillator circuit 3 is clamped to the minumum of the using frequency range until time T1, and lamp waveform (c) is generated through lamp-up circuit 5 when lead-in order signal (b) of the variable frequency oscillator is applied via input data (a) at time T1. With the votage rise of waveform (c), frequency fv of circuit 3 is raised up to be equal to input data frequency f1. Then signal (d) is produced at frequency comparison circuit 4 to set switch circuit 6 to the opposite side. As a result, the phase lock loop is formed: phase comparator 1 filter 2 circuit 3 comparator 1. In this way, the lead-in circuit is made in the 2-stage structure, thus ensuring formation of a variable frequency oscillator featuring a wide range of the lead-in frequency as well as the reduced output jitter. |
