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https://designers-guide.org/forum/YaBB.pl Design >> Mixed-Signal Design >> Sigma-Delta Mod: Spurious tone https://designers-guide.org/forum/YaBB.pl?num=1195294015 Message started by neoflash on Nov 17th, 2007, 2:06am |
Title: Sigma-Delta Mod: Spurious tone Post by neoflash on Nov 17th, 2007, 2:06am In text book from Temes, 2nd order modulator suffer non-linearity from quantizer and thus contains tone in spectrum. Why 1st order modulator does not suffer same problem and looks spur free? |
Title: Re: Sigma-Delta Mod: Spurious tone Post by Berti on Nov 18th, 2007, 10:32pm Hi Neoflash, which text book are you referring to? Which chapter? Because I think you are confusing different issues. I guess what you mean are idle tones, which might be a problem in single-bit low-order (1st&2nd order) modulator. Please post the full reference of the text book to clarify the question. Regards |
Title: Re: Sigma-Delta Mod: Spurious tone Post by neoflash on Nov 19th, 2007, 6:04am Book named: Delta-Sigma Data Converters. by Temes and Schreier In figure 3.6, we see MOD2 contains spurious tone which does not appear in fig2.20 for mod1. |
Title: Re: Sigma-Delta Mod: Spurious tone Post by Berti on Nov 20th, 2007, 12:01am Hi, the name of the book is "UNDERSTANDING delta-sigma data converters". I think the difference is that in fig 3.6 the spectrum is shown using averaging (uncorrelated noise is reduced and the tones are better visible), while in fig. 2.20 no averaging is used and it is therefore hard to distiguish between noise and tones. But in general a first-order modulator is worse than second-order in terms of tonal behavior. Regards |
Title: Re: Sigma-Delta Mod: Spurious tone Post by neoflash on Nov 20th, 2007, 5:45am Oh, that's good to learn about it. Author emphasized tones in 2nd order MOD, so it is a bit confusing. Thanks for this clarification. |
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