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引言在CATV系统中,噪波常以电视画面带有均匀分布的“雪花”状干扰出现,严重时甚至使节目无法收看,这时即使将输入电视机的用户电平增至最大也无济于事。这是一种系统的内在干扰,原则上讲任何CATV系统要完全消除这种干扰是不可能的,只能通过各种努力将噪波干扰减弱至不影响收看的程度。在CATV系统内的各种带电阻性的无源器件和各种有源器件都是噪波干扰源。它们所产生的噪波对系统的干扰程度,一方面取决于它们在系统中的设置位置,另一方面取决于它们自身产生的噪波功率大小。一、无源器件中的噪波在CATV系统中,电缆、分支器、分配器、阻抗变换器、衰减器,甚至一切带电阻性,使传输信号产生损失的无源器件都必然产
Introduction In CATV systems, noise often appears as a “snowflake-like” interference in a TV picture with even distribution. Even in severe cases, the program can not be watched. In this case, it will not help to maximize the user level of the input television. This is a systematic internal interference. In principle, it is impossible for any CATV system to eliminate such interference completely. Only through various efforts can the noise interference be reduced to such an extent that it does not affect the viewing. Various resistive passive devices and various active devices in the CATV system are noise sources. The degree to which they interfere with the system depends on the one hand they are placed in the system and on the other hand on the power of the noise they generate. First, the passive components of the noise In the CATV system, cables, splitters, splitters, impedance converters, attenuators, and even all with resistive, so that the transmission signal loss of passive devices are bound to produce