Hi all:
The attached graph is the measurement result of designed 2nd 1bit sigma-delta modulator, It looks that many harmonic tones in the low frequency.
(simulation is 16bit, measurement is almost 10.5bit)
Please help to analystic what's design errors may causing this result.
Thanks a lot.
They are not harmonics but rather low frequency oscillations (maybe common-mode stability?).
I believe your problems are the tall 2nd and 3rd harmonics.