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小数分频技术可用作同步脉冲的产生,以及各种小数分频和倍频的实现,也可以在合成信号源中作为频率基准。在625行的 PAL 制彩电系统中,为使行频信号(2LF)与它的副载波信号(SC)同步,行频信号最好由副载波信号分离而得。现在我们就以行频信号如何从副载波信号中分离出来,讲述小数分频技术的作用和原理。因为副载波信号频率和行频信号频率各为f_(SC)=4433618.75Hz=11×25×25×644.89Hzf_(2LF)=31250Hz=25×25×25×2Hz所以f_(SC)/(11×25×25×644.89)=f_(2LF)/(2×25×25×25) (1)这样f_(2LF)=(5×1000)/(11×64489)f_(SC) (2)从式(2)可以看到,副载频通过64489分频、11分频、1000倍频、5倍频就成了行频。但实际上副载波信号经64489分频后得到68.75Hz。这样低的频率信
The fractional frequency division technique can be used as a synchronization pulse generation, as well as a variety of fractional and octave implementations, or as a frequency reference in a composite signal source. In a 625-line PAL color system, the horizontal frequency signal is preferably separated from the subcarrier signal in order to synchronize the line frequency signal (2LF) with its subcarrier signal (SC). Now we will be on the line frequency signal from the subcarrier signal separation, about the role of fractional crossover technology and principles. Since the subcarrier signal frequency and the horizontal frequency signal frequency are each f SC = 4433618.75 Hz = 11 25 25 25 64.89 Hzf 2LF = 31250 Hz = 25 25 25 25 Hz, f SC / 11 25 × 25 × 644.89 = f 2LF / 2 × 25 × 25 × 25 f 2LF = 5 × 1000/11 × 64489 f SC From the equation (2) As you can see, the subcarrier frequency is 64489, 11th, 1000 times, and 5 times the frequency. But in fact the subcarrier signal is divided by 64489 68.75Hz. Such a low frequency letter