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Z domain model for this sigma-delta modulator (Read 3584 times)

neoflash Community Fellow Offline Mixed-Signal Designer Posts: 397	Z domain model for this sigma-delta modulator Jan 21^st, 2009, 4:52am This model is different from traditional modulator. Could any one help derive the Z-domain model for this modulator? I have one in mind but that looks involves a (1-Y) scaler at input. Thus make it looks strange. Hope some people familiar with this could help.
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Berti Community Fellow Offline Posts: 356	Re: Z domain model for this sigma-delta modulator Reply #1 - Jan 21^st, 2009, 10:15pm Hi neonflash, To me it looks that this model consist of discrete-time, continuous-time and non-linear blocks. Besides choosing a linearized model for the quantizer one needs to know how the switches work in order to apply the correct transformation. Regards
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neoflash Community Fellow Offline Mixed-Signal Designer Posts: 397	Re: Z domain model for this sigma-delta modulator Reply #2 - Jan 22^nd, 2009, 5:05am We could treate Integrator as Z^-1/(1-Z^-1)
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ywguo

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Re: Z domain model for this sigma-delta modulator
Reply #3 - Jan 23^rd, 2009, 5:45pm

neoflash,

I guess a and b all independent inputs. Y is the output. As the quantized output Y is not fed back to the input, the quantization noise is not modulated actually. What I have derived is shown below.

Y(Z)=a(Z)(z^-1/(1-z^-1)) + E(Z); if Y(Z-1)<0
Y(Z)=b(Z)(z^-1/(1-z^-1)) + E(Z); if Y(Z-1)>0

Yawei

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neoflash Community Fellow Offline Mixed-Signal Designer Posts: 397	Re: Z domain model for this sigma-delta modulator Reply #4 - Jan 24^th, 2009, 1:33am Then, how we compute the TF for Y, from a and b?
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