Theory of lowpass and bandpass sigma-delta modulation

One-bit oversampled or sigma-delta analogue-to-digital conversion has been the subject of much research attention in recent years, finding use in a wide variety of applications. Theoretical analysis of this conversion method has been complicated by its nonlinear nature, precluding the application of standard linear circuit analysis methods. In recent years a number of researchers have undertaken a study of sigma-delta modulation based on nonlinear methods. This paper provides a summary of the results thus obtained, including results not previously published.