在有线电视的双向改造过程中，克服漏斗噪声一直是难点。笔者从漏斗噪声的形成入手，分析其产生的来源、形成机理、分布规律、各自的频谱分布特点等，目的是为了找到降低漏斗噪声的途径。侵入早噪声对双向有线电视网的影响最大，其大部分来自于用户室内。CableModen数量的增加不会显著增大漏斗噪声的幅度。在室外线路中，电缆接头是噪声产生与侵入的主要根源，很容易威胁到整个上行通道的安全。

The funneling effect of noise is the main difficulty in two way CATV modification works. This paper discusses the source of noise and interference, the mechanism to form noise funneling, the regularities of distribution, the characteristics of the spectrum, etc. The purpose is to find the way of reducing funnel noise. The invading noise has the greatest effect on the upstream of two way CATV system, which mainly comes from the indoor of the users. The increase of the number of cable modem will not obviously make greater funneling noise. The cable connectors are the main source of producing and invading noise in outdoor cable network, which is a threat to the safty of the whole upstream channel.

TN943.6 TN941.2