| 摘要 |
PURPOSE:To enable a cheap ceramic vibrator to be used for a VCO by patrolling color burst through a delay means in a period of time except the color burst is inputted to a phase comparison means, making this patrolling output to be the reference input of the said phase comparison means and extending the pull in range of a PLL circuit. CONSTITUTION:The delay means 7 having the delay time of the integral number folds of a chrominance subcarrier cycle is provided, the color burst is patrolled through the delay means 7 in the period of time except the color burst is inputted to the phase comparison means 3 and this patrolling output is made to be the reference input of the phase comparison means 3. Therefore, frequency is raised by repeating the color burst. Thus, the pull in range of the PLL can be extended. Besides, the cheap ceramic vibrator of which Q is small can be used for the voltage control type oscillator (VCO). |
