A prototype bandpass Sigma-delta modulator employing crystal resonator

Abstract

This paper describes an initial work on a second-order bandpass Sigma-delta modulator employing crystal resonator. The aim of this work is to explore the possibilities of realizing bandpass sigma-delta modulator using non-electronic resonators, such as micro-mechanical resonators. The initial study is based on crystal resonators as they have similar characteristics as the other types of resonator and are readily available. In order to obtain the desired loop transfer function, a compensation circuit is proposed to cancel the anti-resonance in the crystal resonator. The modulator chip is fabricated in a 0.6-μ m CMOS process. The bandpass noise shaping is demonstrated in the experiment with a 1- and 8-MHz crystal resonator, respectively. © 2005 Springer Science + Business Media, Inc.