Analysis and simulation of a cascaded delta delta–sigma modulator.pdfVIP

Computer Standards Interfaces 23 Ž2001. 103–110 rlocatercsi Analysis and simulation of a cascaded delta delta–sigma modulator Dileepan Joseph ), Lionel Tarassenko, Steve Collins Engineering Science, UniÕersity of Oxford, Parks Road, Oxford OX1 3PJ, UK Abstract This paper analysis 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. Keywords: Delta; Delta–sigma; Cascaded; Prediction; Noise shaping 1. Introduction ing the modulator complexity and oversampling ra- tio. Several architectures have been developed but The advantages of oversampled modulation for first- and second-order delta–sigma modulators re- analogue-to-digital ŽArD. conversion are well main popular because of their