| 摘要 |
PROBLEM TO BE SOLVED: To use the frequency of an optical integer-multiple compared with the frequency of a reference clock signal by preparing a digital VCO having an addition number variable counter circuit and a circuit which generates a synchronous reproduction clock signal, based on the output pulse signal of the VCO. SOLUTION: A phase comparator 2 outputs a signal, in accordance with the difference between the phase ϕin of an input pulse signal fin and the phase ϕout of a synchronous reproduction clock signal. The signal outputted from the comparator 2 is equal to 1 and 0, when the phase ϕin is larger and smaller than the phase ϕout, respectively. An LPF counter 4 performs the up-counting and down-counting operations, when the output of the compactor 2 is equal to 1 and 0 respectively and then outputs a carrying signal CA and a borrow signal BO when the count value is larger than the 1st set value and smaller than the 2nd set value, respectively. A digital VCO outputs a pulse signal fc±Δf of the frequency, according to the set addition number. Then a 1/N counter 8 outputs a reproduction clock signal, based on the signal fc±Δf. |
