关于sigma delta modulator 的噪声搬移作用

bartuc

sigma delta modulator的噪声传递函数有一个noise shaping的现象，把低频（或者通带）噪声推到高频，然后再把高频噪声滤除。

robicyang

SDM的噪声成型是通过过采样将噪声展开到更大的频带内，然后用反馈衰减低频噪声而增强高频噪声从而将噪声从低频搬移到高频，最后再用数字滤波器将高频噪声滤掉，当然数字滤波器不是SDM的内容

mars419

thanks for share

dgylablab

好，谢谢！

wangfei519

感謝大大無私的分享。

vency2008

顶！正在学习中，下载看看。谢谢

mmic1978

   

原帖由 prof3 于 2009-3-7 09:48 发表

                               
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Basically, SDM has a high pass noise shaping in many case of the FNPLL design. You can design a SDM with effective bandwidth lower than the PLL loop bandwidth so that the SDM noise will be removed by ...

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fu20094376

thanks!

waley

那對於 SSC 又要如何考慮?
SDM's OSR/Order/
PLL's bandwidth 要如何決定 ?

prof3

   

原帖由 waley 于 2009-9-13 00:41 发表

                               
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那對於 SSC 又要如何考慮? SDM's OSR/Order/ PLL's bandwidth 要如何決定 ?

For SSC case, However it is a little bit different. The thing is depending on what the profile of SS is. In general, SS frequency must be low enough so that its shape is NOT corrupted by the loop. In case the SS frequency is comparable to PLL BW, there is a must to do something like pre-shaping before entering SDM loop so that the final SS shape still looks ok