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[SOLVED] modeling DS ADC problem: different result using delsig and SDToolbox

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mingpangzi

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Hi,

I am modeling a 4th order 1-bit quantizer DS ADC with OSR of 64. The architecture I used is "CIFF".
1. First, I start with the tool "delsig" from matlab toolbox, using dsexample1. It works quite nice. The estimated SNR is about 104dB. And I calculated the co-efficient with scaling: a,g,b,c. The spectrum seems OK.
delsig_spectrum.png

2. The I used the SDToolbox which is a simulink model. The co-efficient I used is from the delsig. I try to verify it. However, I didn't see any noise shaping in the spectrum. Thus, the SNR is bad, only 16dB. However, the output is still stable.

simulink_model.png
View attachment spectrum_sdtoolbox.bmp
View attachment integrator_output.bmp

If some one knows why, I will be very appreciated!
Thanks!
 

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