| 摘要 |
PROBLEM TO BE SOLVED: To obtain the control method extending a frequency lock width with less noise component by obtaining the difference between a variation signal and plural reference signals with difference phase differences, comparing difference signals in outputs and selecting a difference signal providing a minimum phase difference at all times. SOLUTION: A 2nd reference signal R2 with a phase difference of πfrom the phase of a reference signal R is obtained from a phase variable circuit 10 inputting the reference signal R. The reference signal R and a variation signal V are given to a 1st phase comparator circuit 11, from which signals U1 , D1 are outputted. The 2nd reference signal R2 and the variation signal V are given to a 2nd phase comparator circuit 12, from which signals U2 , D2 are outputted. A selection circuit 13 that selects finally a 1st difference signal or a 2nd difference signal whose phase difference with respect to the reference signal R is within ±2$π gives a switching signal to a changeover circuit 14. The changeover circuit 14 acts like an output means that selects the 1st difference signal or the 2nd difference signal finally. |
