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本文阐述PAL色度信号的正交变换原理、时域分析、频谱特性和解调技术.它用相延迟时间等于行周期的延迟线和加减电路,对PAL色度信号进行正交变换.正交变换输出半行频色同步信号,可用于调整正交变换器和行轮换开关的识别信号.文中所得结果,经系统实验证明,理论分析和实验完全一致.一、正交变换原理PAL色度信号的正交变换,是把原来由U与V分量组成的PAL色度信号,变成由U与V分量之和与差的新的正交的色度信号.这种变换关系的基础,是假定实际生活中的相邻行的彩色信息近似相等,色度信号的幅度、相位一定.这样采用64微秒延迟梳状滤波器,使原来延迟梳状分离PAL色度信号的延迟行与直通行相位差为180°,变为相位差为90°的正交关系,这样做的结果,同样能平均色度信号在传输过程中引起的相位误差,克服NTSC制的相位敏感性.
This paper describes the principle of orthogonal transform of PAL chrominance signals, time-domain analysis, spectral characteristics and demodulation techniques.It uses the delay line with phase delay equal to the line period and the addition and subtraction circuits to orthogonally transform PAL chrominance signals. Alternating half-line output color-frequency synchronization signal output, can be used to adjust the orthogonal converter and the line switch for the identification signal. The results obtained in the system experiments show that the theoretical analysis and experiment exactly the same. First, the orthogonal transform principle PAL Chromaticity The orthogonal transformation of a signal is a new orthogonal chrominance signal that is made up of a PAL chrominance signal originally composed of U and V components into a sum and a difference of the U and the V components.The basis of this transformation is Assuming that the color information of adjacent lines in real life is approximately equal, the amplitude and phase of the chrominance signal are constant, thus the delay line and the straight line of the original delayed comb-shaped PAL chrominance signal are delayed by the 64 microsecond delay comb filter, The phase difference is 180 ° and becomes a quadrature relationship with 90 ° phase difference. The result of this is that the phase error caused by the transmission of the chrominance signal can also be averaged to overcome the phase sensitivity of the NTSC system.