文档介绍：数字电视的主要测量技术指标
actively carry out the law on civil air defense education, drawn out of the air defense in Pinglitasks. 5, further standardize internal management, improve staff quality. Adhere to the
actively carry out the law on civil air defense education, drawn out of the air defense in Pingliang city Building under easy fare, daily special inspection and regulation, overfulfilled the province upper and lower knots of up to 500,000 yuan fee collection tasks. 5, further standardize internal management, improve staff quality. Adhere to the
actively carry out the law on civil air defense education, drawn out of the air defense in Pingliang city Building under easy fare, daily special inspection and regulation, overfulfilled the province upper and lower knots of up to 500,000 yuan fee collection tasks. 5, further standardize internal management, improve staff quality. Adhere to the
机顶盒
MER
Pro FEC
BER
Post FEC
BER
64QAM
优良
32dBuv
-8
>-9
正常值
28dBuv
-7
-8
临界值
24dBuv
-6
-7
第二步：当这些指标恶化的时候，应该对其它指标进行详细的测量，判断造成网络质量恶化的原因。因为MER的恶化是最主要的因素，它将直接导致BER的下降并最终影响用户接收机的接收效果。所以因主要测试调制质量参数，找出问题原因。
调制质量参数主要有：调制误差率、载波抑制、幅度不平衡、正交误差、相位抖动，RS解码前误码率等。其中调制误差率反映了调制的总体质量；载波抑制、幅度不平衡等反映调制中可能引起误差的主要原因；RS解码前误码率那么反映了整个信道的可靠性的性能。对数字调制的直接测量是找到信号失真源头的有用工具。调制质量的估价是放在数字解调之后，自适应均衡器附近.
第三步：利用星座图进行逐级排查。
当然我们一般的测试工作只需要做第一步就可以，当网络有问题的时候做第二，三步；而且绝大多数时候我们第二，