Natural compression and expansion characteristics of asynchronous Sigma-Delta ADC

The paper analyzes the impact of non-linearity of asynchronous Sigma-Delta analog-to-digital converter (ASD-ADC) characteristics on the quantization process. The ASD-ADC is considered as time-interleaved multi-resolution converter that employs two different characteristics for signal processing alternately. As shown in the paper, the classical uniform quantization of the asynchronous Sigma-Delta modulator (ASDM) output signal by time-to-digital converter is ineffective due to the different shapes of ASDM characteristics that provide disparity of converter resolution transformed into the signal value domain. A need to introduce extra compensation techniques to cope with the problem of balancing the ASD-ADC resolution and shaping the signal-to-noise ratio is emphasized.