Hi
  I am trying to find out how to measure the SNDR of a sigma delta modulator (SDM) ? Suppose your base band is up to B.  After B Hz the output spectrum of SDM starts to rise. Suppose you apply the tone of BHz there would be harmonics (2B , 3B ...) . How would you measure/simulate ? Would not these be buried in the noise? And if they stick out then their level would be already gained up (?) because of the gain of SDM at frequenecies outside B.
 So how exactly would you characterize the SDM distortion? Is the choice of input tone at B Hz is correct? or should I apply the tone such that the harmonics still fall in the base band?

Cheers  :)