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在 U 型机与1.27cm 家用录像机中,由于受到记录带宽的限制及时基抖动等因素的影响,需将彩色副载波的频率向低变换至600～700kHz,即通常说的彩色低域变换。在低域变换中产生了一些新的现象。本文对其中的色轴置换现象、彩色带宽压缩现象、相位抖动下降现象和如何决定锁相环中的频率问题进行分析。一、色轴置换现象在下变换色信号频率过程中,本振频率高于电视系统的色信号副载波频率。下边频的色信号在矢量图上产生色轴(红轴与蓝轴)位置对换现象,而色同步向前90°。因为新的色坐标沿着原直角坐标系第一、第三象限45°对角线空间旋转180°,此对角线便成为新老座标的镜面线。为观察矢量图方便起见,笔者以
In the U-shaped machine and 1.27cm home video recorder, due to the limitations of recording bandwidth and timing jitter and other factors, the color sub-carrier frequency to be low to 600 ~ 700kHz, the so-called color low-domain transform. There are some new phenomena in the low-range transform. In this paper, the color axis displacement phenomenon, the phenomenon of color bandwidth compression, the phenomenon of phase jitter reduction and how to determine the frequency of PLL are analyzed. First, the color axis displacement phenomenon In the process of converting the color signal frequency, the local oscillator frequency higher than the television system, the color signal subcarrier frequency. The lower frequency chrominance signal produces a color swatch position (red axis and blue axis) on the vector image, while the color sync forward 90 °. Because the new color coordinates are rotated 180 ° along the 45 ° diagonal space in the first and third quadrants of the original Cartesian coordinate system, this diagonal becomes the mirror line of the old and new coordinates. To facilitate the observation vector, I author