Distortion mechanisms in 1-bit Sigma-Delta modulators

Abstract—One bit sigma-delta modulators (SDM) are used to convert analog signals to digital signals using a feedback loop. This feedback loop consists of a 1 bit quantizer and a frequency selective filter. The feedback loop however, does not attenuate memoryless distortion that occurs before the filter like a classical feedback loop would do. The reason for this is the binary nature of the feedback signal. Introducing a reconstruction filter in the feedback path can solve this problem. By lowering the cutoff frequency, better suppression of the memoryless distortion is obtained. Lowering the cutoff frequency too much can cause the system to not be able to suppress the distortion anymore, because the quantizer of the SDM will start to clip.