在发送端,彩色电视信号经过编码后再传送.在接收端,重现彩色图象时,需将编码信号进行反变换,即所谓解码,解码就是将编码信号逐个解出,还原为三个基色信号电压.作者制作了延时型PAL解码器,这是目前彩色电视机中广泛采用的一种.解码器由亮度通道和色度通道组成.色度通道由4.43MHz带通滤波器、解码集成电路TA7193P、梳状滤波器和矩阵兼末级视放电路组成.在调试过程中,采用了矢量点调整法,它具有简单、快速、直观、精确的优点,并且能把该解码电路调整到最佳状态.所需要的仪器除了一台彩色信号发生器外,还需一台具有x轴输入、少轴输入的通用示波器.矢量调整法的基本要点就是把ν(R-y)加到示波器的y轴,把u(B-y)加到x轴,在x,y平面上观察解码输出.当β,α分别是常数时,示波器看到的画面是矢量点图;当β,α随时间变化时,画面上就出现矢量点轨迹图,其中β和α分别是(R-Y)和(B-Y)轴解调角误差,作者用四矢量法调整梳状滤波器,给出了关于梳状滤波解调误差的分析公式及现象。 At the transmitting end, the color television signal is encoded and then transmitted.On the receiving end, to reproduce the color image, the encoded signal needs to be inverse transformed, that is, the so-called decoding, the decoding is to decode the encoded signals one by one, and restore to three primary colors Signal voltage. The author made a delay type PAL decoder, which is widely used in color TV today. The decoder consists of a luma channel and a chroma channel. The chroma channel consists of a 4.43MHz band-pass filter, decoding integrated Circuit TA7193P, comb filter and the end of the matrix as the last circuit. In the debugging process, using the vector point adjustment method, it has the advantages of simple, fast, intuitive and accurate, and the decoding circuit can be adjusted to the most In addition to a color signal generator, a universal oscilloscope with x-axis input and few axis input is required for the required instruments. The basic point of the vector adjustment method is to add ν (Ry) to the y-axis of the oscilloscope , The u (By) added to the x-axis, in the x, y plane observation decoding output.When β, α are constant, the oscilloscope to see the picture is a vector point map; when β, α changes with time, the screen On the vector point trajectory appears, where β and α are the error angles of (R-Y) and (B-Y) axis demodulation respectively. The author adjusts the comb filter by the four-vector method, and gives the analytical formula and the phenomenon about the demodulation error of the comb filter.