| 摘要 |
PURPOSE:To apply a device to all systems of NTSC, PAL and SECAM, by using a part of delay lines in common. CONSTITUTION:Relation between horizontal scanning frequency fh and chrominnance subcarrier frequency fsc of a PAL system is 1/4 line off-set of fsc=(n-1/4) fh+25Hz, and on the other hand, it is 1/2 line off-set in case of an NTSC system. Accordingly, when fsc of the NTSC system is converted to that which is equal to fsc of the PAL system, the extent of delay of a delay line 10 is made 1H-1/4lambda, (lambda=1/fsc) by disregarding a component of 25Hz. Since a chrominance subcarrier is 180 deg. out of phase at input/output sides of the delay line 10, a chrominance signal can be obtained from a subtracter 24. When the extent of delay of a delay line 11 is made 1H-1/4lambda, a total extent of delay of the delay lines 10, 11 becomes 2H-1/2lambda the chrominance subcarrier becomes in phase at an input side of the delay line 10 and an output side of the delay line 11, and a chrominance signal can be obtained from an adder 12. |
