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本文着重讨论以2fs(?)作为取样频率对PAL制彩色电视信号取样时的一些新问题。文中论述了前置梳状滤波器和取样相位间的关系,认为在取样环路中设有前置梳状滤波器,可允许取样相位有较大的偏差,否则取样相位偏差引起的色度信号失真,是PAL制式补偿不了的。文中指出,在取样之后,色同步信号变成隔行传送,但在经过梳状滤波器以后可得到恢复。文中分析了取样保持电路,认为设保持电路不会造成图象质量恶化。此外,还讨论了延迟线的延时精度对图象质量的影响。最后给出了对PAL制信号进行亚取样等实验的结果。
This article focuses on some of the new problems when sampling a PAL color television signal with 2fs (?) As the sampling frequency. In this paper, the relationship between the pre-comb filter and the sampling phase is discussed. It is considered that the pre-comb filter is provided in the sampling loop, which can allow a large deviation of the sampling phase. Otherwise, the chrominance signal caused by the sampling phase deviation Distortion, PAL can not be compensated. The article pointed out that after the sampling, the color burst into interlaced transmission, but after the comb filter can be restored. In this paper, the sample-and-hold circuit is analyzed, and it is assumed that the holding circuit does not deteriorate the image quality. In addition, the effect of delay line delay accuracy on image quality is also discussed. Finally, the sub-sampling results of the PAL signal are given.