网络传输产品中数字高阶QAM调制信号的信号质量瞬时恶化的测试及避免方法

Methods to Test and Prevent the Intermittent Signal Loss of CATV High-order QAM Signal Transmission

网络传输包括HFC(Hybrid Fiber Cable)产品正在往智能化方向发展:远程配置修改参数,自动幅度调整等等。为实现电路参数如放大器的增益、斜率等的调整,数字步进衰减器被广泛地使用。而在现阶段网络改革中,为了实现高数据速率信号的传输,使用越来越高的数字QAM调制阶数,如256QAM,4096QAM等,因此对信噪比(SNR)的要求越来越高。数字衰减器值的变化更容易引起瞬时误码的产生,造成BER恶化,从而引起丢包(Packet Loss),造成电视图像的卡顿等。主要探讨如何测试以及预防高阶数字QAM信号由于数字衰减器的变化造成的瞬间BER恶化以及丢包。

Network Transmission products（including HFC：Hybrid Fiber Cable）are becoming more and more intelligent：remote modification of parameters,automatic amplitude adjustment and so on.Digital step attenuators are widely used for the adjustment of circuit parameters such as amplifier gain,slope,and the like.In the current stage of network reform,higher and higher digital QAM modulation orders,such as 256 QAM and4096 QAM,are used in order to realize the transmission of high data rate signals.Therefore,the requirements for the signal to noise ratio（SNR）become increasingly high.The change of the digital attenuator value is more likely to cause the generation of instantaneous error,resulting in deterioration of the BER and thus causing packet loss and a stuck image of the television.This article mainly discusses how to test and prevent the instantaneous BER deterioration and packet loss caused by the change of the digital attenuator in the high-order digital QAM signal.