Patent ID: 7693246

Claim:
A frequency control device comprising: an oscillation circuit outputting a clock having a frequency corresponding to a control signal; a converter sampling an analog input signal having a predetermined pattern based on the clock and converting the signal to a digital signal; and a frequency detection device detecting an object to be a sync pattern from a changing trend of the digital signal, generating a frequency information for controlling a reproduction clock based on the detected object to be the sync pattern, and outputting the frequency information as the control signal to the oscillation circuit, wherein the frequency detection device comprises a peak bottom value detection unit detecting a peak value and a bottom value from an input digital signal, a setting unit setting a predetermined hysteresis with respect to the detected peak value and bottom value, a comparison judgment unit comparing the hysteresis values of the peak value and the bottom value with the input digital signal, detecting a pattern having a long inversion interval, judging whether or not a pattern having a long inversion interval at an opposite side to the peak or the bottom is continued, and determining a case where the pattern having the long inversion interval is continued as an object to be a frame sync pattern, and a measurement unit counting a number of judging clocks of the object to be the frame sync pattern during determining the object to be the frame sync pattern, and measuring the number of clocks as a length of the object to be the frame sync pattern.