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https://designers-guide.org/forum/YaBB.pl Design >> Mixed-Signal Design >> Sigma-Delta MOD1: Quantizer gain https://designers-guide.org/forum/YaBB.pl?num=1195293912 Message started by neoflash on Nov 17th, 2007, 2:05am |
Title: Sigma-Delta MOD1: Quantizer gain Post by neoflash on Nov 17th, 2007, 2:05am In text books, the MOD1 z-domain model assumed quantizer gain as 1 for analysis. Is this correct? What if the gain is different from 1, any analysis done there? |
Title: Re: Sigma-Delta MOD1: Quantizer gain Post by vivkr on Nov 19th, 2007, 2:32am Hi neoflash, The quantizer gain can only be assumed to be 1 for multibit quantizers and for reasonably large signal swing at quantizer inputs. As far as I know, the quantizer gain needs to be calculated from the signal statistics for a 1-bit quantizer. And the textbooks also do it this very way. I would recommend that you look at the textbook by Schreier & Temes or the TCAS paper by Baird & Fiez. Regards Vivek |
Title: Re: Sigma-Delta MOD1: Quantizer gain Post by neoflash on Nov 19th, 2007, 6:09am thanks for your reply. Then why in z-model, the gain is assumed to be "1" to get desired NTF and STF? |
Title: Re: Sigma-Delta MOD1: Quantizer gain Post by vivkr on Nov 21st, 2007, 7:34am Which z-model do you mean??? If it assumes a gain of 1, then there is the general assumption that the quantizer is not being overloaded. For a 1-bit quantizer, I would suggest that one still does not set the gain blindly to 1. However, it is probably used because it is easy to set it to 1. The references I mentioned cover the topic in greater detail. Regards Vivek |
Title: Re: Sigma-Delta MOD1: Quantizer gain Post by Berti on Nov 21st, 2007, 10:27pm Hi Neonflash, In the classical model, the quantizer gain has to be 1 when you assume a unity closed-loop gain for the modulator. However, Vivek is right. That gain will change depending on the input signal. Signal-statistics are usually used to calculate the quantizer gain (and to determine stability). Regards |
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