acezhy
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Hi all,
The digital sigma delta modulator is a 3rd order mash 1-1-1 digital modulator and the output range is -3~4. The operation frequency is fs. What I care is the output noise magnitude at N*fs/2. Firstly, I did a transient simulation and do FFT for the sdm output number. By observing the spectrum, the magnitude points at N*fs/2 in decibel has a -20dB/dec slope. On the other hand, however, if I calculate the spectrum in frequency domain in Mathcad. The magnitude values at N*fs/2 have no difference. Could anyone help me explain this? Did I miss something?
Thank you very much! -Ryan
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