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Output of interest of Sigma delta Modulators (Read 3001 times)

cdbular New Member Offline Posts: 8	Output of interest of Sigma delta Modulators Apr 15^th, 2008, 10:25pm Which signal in sigma delta modulators in general (single bit, mulibit, order N) should be spectrally analyzed (PSD, SNR), the digital output? the integrator output? in order to evaluate converter performance
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Berti Community Fellow Offline Posts: 356	Re: Output of interest of Sigma delta Modulators Reply #1 - Apr 15^th, 2008, 10:35pm Hi, In general you can analyzed any signal But usualy the wanted spectrum is found at the modulator output (ADC : digital out; DAC, digital SDM : after truncation). Regards
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cdbular New Member Offline Posts: 8	Re: Output of interest of Sigma delta Modulators Reply #2 - Apr 16^th, 2008, 7:13am Thanks for you reply berti. But in the case of multibit architechures, how can I analyze the output spectrum?
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Berti

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Re: Output of interest of Sigma delta Modulators
Reply #3 - Apr 16^th, 2008, 10:26pm

I assume you are designing an ADC: Take the output of the quantizer, which is usually termomether-decoded and
perform a FFT on that. (Or take the output after the therm. to binary decoder, if there is one).

Example:

Quatizer (therm.) output : 000 -> binary : 00 -> value : -1
Quatizer (therm.) output : 001 -> binary : 01 -> value : -1/3
Quatizer (therm.) output : 010 -> binary : 10 -> value : 1/3
Quatizer (therm.) output : 100 -> binary : 11 -> value : 1

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