A Kind Of Sigma-Delta Modulator Applied In Portable Audio System

With the rapidly development of integrated circuits,The Sigma-Delta modulator uses oversamping and noise shaping as its core technology getting more and more widely use.Compared with traditionally Analog-to-Digital converter,The Sigma-Delta modulator has the ability of high speed,high resolution,and low power dissipation.Especially in portable audio application it needs high resolution and low power dissipation,so Sigma-Delta modulator is a best choice.In this project,firstly,analysis the fundamental of Sigma-Delta working principle and its constructing manner,comparing and analyzing the advantages and disadvantages of various kinds of modulator,considering the proposed 14 bit resolution,the selection of important parameter of modulator is completed.The second order 1 bit architecture with oversamping rate 256 times is adopted in this project.Secondly,the behavior model of the selected modulator architecture is simulated in MATLAB.Considering in ideally conditions,with the input signal bandwidth within 20 k Hz the signal-to-noise(SNR)can achieve 101.6d B,after calculation,satisfying the design requirement of 14 bit resolution.Subsequently,the analysis of non-ideality of Sigma-Delta modulator is presented.After behavior simulation,circuit level design and simulation is presented.In this section concerning to what this project is aim to and the non-ideality of active integrator we take passive integrator as our integrator design.At the same time,we also design comparator circuit,delay circuit,two clock phase non-overlap circuit,and so on.And simulate them one by one,ensure they get their desire value.Put them all together and simulate it in Cadence SPECTRE,Finally,the SNR of this Sigma-Delta modulator is 96.2d B with 10 MHz sampling frequency and 20 k Hz input signal bandwidth.The result is in accord with the behavioral simulation and the proposed architecture.