Analysis and simulation of a cascaded delta delta–sigma modulator

This paper analyses and simulates a delta delta–sigma modulator, the cascade combination of a delta modulator and a delta–sigma modulator. Using prediction, the delta modulator reduces the dynamic range of a signal prior to quantisation. Using noise shaping, the delta–sigma modulator cancels the error of the delta modulator. Performance is evaluated with input signals from a random noise process, composed of a high dynamic range narrow-band process and a low dynamic range wide-band process. Integrator leakage in the delta modulator and DAC mismatch between the two modulators may complicate implementation. The cascaded modulator outperforms conventional modulators of similar order when there is a degree of correlation between consecutive samples of the input process. q 2001 Elsevier Science B.V. All rights reserved.