论文部分内容阅读
宽带放大器(以下简称放大器)性能的优劣能直接影响CATV系统的质量,放大器应在很宽的频带里有很好的交扰调制比和输出电平. 当两个或两个以上电视频道的信号通过放大器时,由于放大器的非线性,一个频道的图像载波会被另一频道的调制波形所调幅.这种情况反应到电视图像上,表现为在接收频道的电视图像上迭加了另一频道的图像,这就是交扰调制干扰.受这种干扰的图像载频没有改变,用滤波器无法滤除.要克服这种干扰,就要减小放大器的输入和输出电平,使放大器工作在线性区.但是,为了提高CATV系统的信噪比和减小重影,就应提高输入和输出电平.因此,要克服交扰调制干扰的根本方法,只能是选用优质放大器. 测试放大器性能的优劣,可以直接测试放大器的线性工作范围,然后等效成交扰调制比,这比直接测试交扰调制比要简单.测试原理如图1所示.
The performance of a wideband amplifier (hereinafter referred to as the amplifier) can directly affect the quality of the CATV system, and the amplifier should have good crosstalk modulation ratio and output level over a wide frequency band. When two or more television channels When the signal passes through the amplifier, the image carrier of one channel is amplitude modulated by the modulation waveform of the other channel due to the non-linearity of the amplifier, which reacts to the television image, appearing as superimposed on the television image of the receiving channel Channel image, this is the crosstalk modulation interference.Is disturbed by the image carrier frequency has not changed, with the filter can not be filtered.To overcome this interference, it is necessary to reduce the amplifier input and output levels, the amplifier work However, in order to improve the signal-to-noise ratio of CATV system and reduce the ghost, we should increase the input and output level.Therefore, to overcome the fundamental method of crosstalk modulation interference, only the selection of high-quality amplifier. Test Amplifier The merits of the performance, you can directly test the linear amplifier operating range, and then the equivalent transaction crosstalk ratio, which is more simple than the direct test crosstalk modulation ratio to be simple. Test principle shown in Figure 1.