harpoon wrote on Aug 21st, 2011, 9:35am:I would expect a 1 bit quantised to produce harmonic tones as well. Are you sure you are not confusing yourself with first order dsm?
A 1-V 140-
W 88-dB Audio Sigma-Delta Modulator
in 90-nm CMOS Libin Yao, Student Member, IEEE, Michiel S. J. Steyaert, Fellow, IEEE, and Willy Sansen, Fellow, IEEE.....
This is the spectrum of 1 bit 3rd order SDM . Compare it with the above (2 bit SDM) :). Quantizer is not the reason . and the rest of the circuit is IDEAL.