High-Precision ?-? Modulator Design For ECG Signal Acquisition

With the development of IC industry to which has been paid more attention recently in China,more and more resources are put into this industry and much more people are engaged in it.IC industry combined with medical industry is a hot topic and ECG monitoring system has become a new research direction.But the research of ECG monitoring system is not matured and there is no specific chip for it in China.This project has designed a high-precision ?-? modulator for front-end ECG signal sampling system based on ECG monitoring system.The data processing flow is that the analog ECG signal is converted into digital signal by ?-? modulator which is,then,sent to DSP for subsequent data processing.Firstly,this dissertation describes the ECG monitoring system,and decided the specifications of analog to digital converter which is the main design in this dissertation according to applying background of analog to digital converter.Comparing the distinction of different analog to digital converters and analyzing their features,the ?-? modulator is considered the best choice for realizing high-precision.Then some of the common used structures of ?-? modulator have been introduced,and the structure of CIFB has been selected after comparing the common used structure.Secondly,this paper studies the system model of ?-? modulator which is a valid method for the determination of the system parameters,such as the number of stages for?-? modulator and the parameter of every stage according to requirement for sampling precision.On this basis,the Matlab simulation software and the root locus method are used to get the parameters' range of the system for stability,and then adjust the coefficient to meet the system requirements.Then consider the non-ideal factors which may arise in the process of implementation the actual circuit,simplified the model of non-ideal ?-?modulator through manual analysis and calculation of different types of non-ideal factors.Take the whole system simulation after the establishment of a non-ideal ?-? modulator model and the simulation result shows that the SNR and ENOB of the ?-? modulator are 103.7dB and 16.94 bits respectively.Then,circuits design is showed in this paper.The system parameters obtained by system modeling of ?-? modulator are very useful to guide the circuit design.In the circuit design process,it is effective to optimize the circuit design process and reduce the number of iterations by using GMID circuit design method.And the chopper structure is applied in the circuits which can improve the performance of ?-? modulator through eliminating the offset voltage and low frequency amplifier noise.SMIC 0.18um technology and 1.8V supply voltage are applied in the circuits design and the circuit's simulation result shows that the SNR and ENOB of the ?-? modulator are 103.3dB and 16.87 bits respectively.Finally,this paper introduces the layout design and the test scheme.The layout of each module circuit is designed,after that the DRC,LVS verification and post simulation are taken as the same as the whole circuits.The post-layout simulation result shows that the SNR and ENOB of the ?-? modulator are 99.6dB and 16.26 bits respectively.