Research On Sigma-delta Modulator And Modeling In Simulink

By imploying oversampling and quantimization noise shaping, Sigma-delta converters can achieve a very high-resolution conversion. Sigma-delta converters are robust against analog circuit imperfection and component mismatch, compared with the traditional Nyquist rate converters. Additionally, these converters are well suited for integration on one chip with other digital circuits. Currently, along with the rapid development of system on chip (SOC), Sigma-delta converters have been widely implemented in many fields.In this thesis, the principle of Sigma-delta modulator is presented firstly. Then the non-idealities which affect the performance of Sigma-delta modulator are analyzed, including sampling jitter, nonlinear on-resistance, kT/C noise and operational amplifier limitation (finite DC gain, finite bandwidth, slew rate and saturation). Furthermore, a time-domain nonideal model of second order sigma-delta modulator is given in SIMULINK. The evaluation of each non-ideality which affects the performance of sigma-detla modulator can be made by using this model. Also, an idea of optimum global design is presented by the use of statistical optimization techniques in this thesis.According to the simulation result of the nonideal model, the specification of each analog block used in modulators is presented, and the detailed circuits are designed. By comparing the simulation results between the nonideal model and transistor circuits, the conclusion can be attained that the nonideal model presented in this thesis performs very well, giving a correct guidance on designing transistor circuits to the IC circuit designers.