dBm0到底是什么意思?

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 楼主| gohunter 发表于 2007-6-24 16:34 | 显示全部楼层 |阅读模式
AN, ce, IO, TE, TI
找了下面的解释,但还是不明白,谁来解解谜底?<br /><br />dBm0&nbsp;is&nbsp;an&nbsp;abbreviation&nbsp;for&nbsp;the&nbsp;power&nbsp;in&nbsp;dBm&nbsp;measured&nbsp;at&nbsp;a&nbsp;zero&nbsp;transmission&nbsp;level&nbsp;point.<br /><br />dBm0&nbsp;is&nbsp;a&nbsp;concept&nbsp;used&nbsp;(amongst&nbsp;other&nbsp;areas)&nbsp;in&nbsp;audio/telephony&nbsp;processing&nbsp;since&nbsp;it&nbsp;allows&nbsp;a&nbsp;smooth&nbsp;integration&nbsp;of&nbsp;analog&nbsp;and&nbsp;digital&nbsp;chains.&nbsp;Noticeably,&nbsp;for&nbsp;A-law&nbsp;and&nbsp;μ-law&nbsp;CODECS&nbsp;the&nbsp;standards&nbsp;defines&nbsp;a&nbsp;sequence&nbsp;which&nbsp;has&nbsp;a&nbsp;0dBm0&nbsp;output.<br /><br />Note1:&nbsp;a&nbsp;consequence&nbsp;for&nbsp;the&nbsp;A-law&nbsp;and&nbsp;μ-law&nbsp;CODECS&nbsp;of&nbsp;the&nbsp;0dBm0&nbsp;definition&nbsp;is&nbsp;that&nbsp;they&nbsp;have&nbsp;a&nbsp;respective&nbsp;3.14dBm0&nbsp;and&nbsp;3.17dBm0&nbsp;maximum&nbsp;output&nbsp;(ratio&nbsp;between&nbsp;the&nbsp;max&nbsp;amplitude&nbsp;of&nbsp;the&nbsp;sinewave&nbsp;and&nbsp;the&nbsp;maximum&nbsp;code).<br /><br />Note2:&nbsp;0dBm0&nbsp;is&nbsp;often&nbsp;replaced&nbsp;by&nbsp;or&nbsp;used&nbsp;instead&nbsp;of&nbsp;digital&nbsp;milliwatt&nbsp;or&nbsp;zero&nbsp;transmission&nbsp;level&nbsp;point.<br />
jimsboy 发表于 2007-6-25 00:14 | 显示全部楼层

1mw的功率

如果是电压就一定要在某个阻抗下.否则无意义
 楼主| gohunter 发表于 2007-6-26 20:18 | 显示全部楼层

在IDT821024的datasheet找到以下定义

0dBm0&nbsp;is&nbsp;defined&nbsp;as&nbsp;0.6832Vrms&nbsp;for&nbsp;A-law&nbsp;and&nbsp;0.6778&nbsp;Vrms&nbsp;for&nbsp;m-law,&nbsp;both&nbsp;for&nbsp;600&nbsp;ohm&nbsp;load.
chunyang 发表于 2007-6-26 21:05 | 显示全部楼层

一般在各种分贝单位中,0是基准

但不同定义的算法和条件不同,楼主其实应该已经知道了,0dBm0指600欧负载下A率有效电压0.6832V及u率有效电压0.6778V为基准参考值,其它值是基准值的相对指标。&nbsp;
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