| 摘要 |
PURPOSE:To pass through an input synchronizing signal only and to reject other noises, by providing a gate circuit which is open through the estimation of leading of an input synchronizing signal at the input of a PLL circuit, in a synchronizing shape circuit using PLL. CONSTITUTION:An input synchronizing signal (a) passes through a gate circuit 1 and becomes a rectangular wave c through being shaped at the 1st monostable multivibrator and is transmitted to a PLL circuit 9. An output synchronizing signal d based on the wave c is obtained from a delay circuit. An output e of a voltage controlled oscillator 4 is shaped to gate pulses f, g at the 2nd monostable multivibrator 6 and applied to the gate circuit 1 via an OR circuit 7, and since the-gate circuit 1 is set through the estimation of leading of the signal (a), noises mixed in other periods can be rejected. If the PLL circuit is unlocked, since the output of the phase comparator 3 is applied to the OR circuit via an integration circuit 8, the gate 1 is kept set independently of the output f of the 2nd monostable multivibrator 6. |
