| 摘要 |
PURPOSE:To detect easily jitter by using a PLL circuit which can not follow the fluctuation of a jitter detecting period signal out of plural kinds of period signals constituting a reproducing EFM signal. CONSTITUTION:A reproducing EFM signal is inputted to the PLL circuit through a comparator COMP and a monostable multivibrator MM. The PLL circuit is constituted so as to follow and respond only to an input signal having a longer period than the period of the variation of a jitter variable to be measured. Therefore, a signal including the fluctuation of the phase of the input EFM signal is taken out from the output of a phase comparator PC. An AND circuit AND extracts a specific period signal P3 having a short period, i.e. a signal P3 modulated at its pulse width by the jitter variable, from the signal Pc. The signal Pc is converted into a phase error voltage and then converted into an effective value by an effective value converting circuit EX.
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