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要彩色电视机重现正确的色彩,就要求本机副载波与电视台的基准副载波严格同频同相,即实现同步,这必须使锁相器工作在优良状态。当锁相电路发生失锁时,接收到的彩条测试图的白、黄、青、绿、紫、红、蓝、黑八条彩带会出现彩虹现象,或叫彩色百页窗现象。本文用失锁时副载波基准轴与电视机本机解调轴之间的相对旋转理论,对这现象进行分析,并提出解决办法。本文将电视发送台的 B′-Y′副载波命名为 U_s,将R′-Y′副载波命名为±V_s,将蓝色色度信号分量命名为 U_F,将红色色度信号分量命名为±V_F,它们的关系如图1所示。
To color television to reproduce the correct color, it requires the local sub-carrier and television reference sub-carrier strictly in-phase with the frequency, that is to achieve synchronization, which must make the phase-locked state work in good condition. When the phase-locked circuit is out of lock, the rainbow, yellow, blue, green, purple, red, blue and black ribbons received by the color bar test chart will appear rainbow phenomenon or color blind window phenomenon. In this paper, the theory of relative rotation between the reference axis of subcarrier and the demodulator axis of TV set is used to analyze this phenomenon and propose a solution. In this paper, we designate the B’-Y ’subcarrier of the television transmitting station as U_s, name the R’-Y’ subcarrier as ± V_s, name the blue chrominance signal component as U_F, and red chrominance signal component as ± V_F , Their relationship shown in Figure 1.