Delta sigma ADC (Start from Scratch design)

[dawson]

Okie. let me start with the signal amplitude.

im using simulink sinewave block attach are the details
a amp=2V sinwave= 2*pi*1000 <-- freq = 1khz..


if i weree to perform an FFT i should be seeing 1 straight line at 1khz???

what code to use to do a FFT from the sinewave? and does the stop time take in consider?

 

[Eminent.Engineer]

Hello Dawson,

if i weree to perform an FFT i should be seeing 1 straight line at 1khz???

In my opinion, since you never obtain an impulse in frequency domain for a pure sinusoid, because of implicit windowing that is taking place, i.e., rectangular windowing because you consider sinusoid over limited time. So applying window (hann, hamming etc) to time domain signal decreases the spectral leakage and improves FFT response.

For better understanding of spectral leakage and windowing, "Understanding Digital Signal Processing by Richard Lyons".

Hope this will be helpful.

 

[dawson]

what about analog design.. have you done any simulation of the DSM . here is my design.. but my output seems to be inverted.. anyone know if im doing anything wrong or can explain to me why my waveform is inverted.


my output bit steam when input at Vmax there should be more 1s at the top however my waveform stated otherwise.



my design is a 1st order SDM..

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by the way are you able to show me how you design your LPF and downsampler?? and also how your output waveform look like?? in time /freq domain