A Design Of Sigma-delta ADC Modulator

Analog to digital converter (ADC) as an interface connected to the analog circuit anddigital circuit, has an important position in the field of high speed digital communications,and high precision sensor signal detection. At present, the ADC determines wholeperformance of the system, The sigma-delta ADC sacrifices speed but in exchange for theadvantage of accuracy,and the performance requirements of the circuit has beensignificantly reduced, The sigma-delta ADC is an effective way to achieve high precision.Sigma-delta ADC is widely used in mobile radio frequency (RF), all kinds of digital audioproducts such as MP3, CD, The resolution can achieve more than16bit. The advantage ofthe sigma-delta modulator is that it puts noise signal frequency to the high frequencyband,and increase the signal-to-noise ratio of the system effectively.The structure reducesthe circuit design time. The advantages are the main reasons for the modulator becomingthe research hotspot in recent years.This thesis describes the theory and design method of sigma-delta modulator. The16bits sigma-delta modulator is designed. Firstly, the initial structure of modulator should bedetermined through the theoretical analysis, and the Matlab simulink are applied toconfirm the structure meeting the design requirements. the quantity of simulation analysisis accomplished to determine the third-order CIFB ring structure,and a sampling rate of256is applied to the input signal sampling requirements.The noise transfer function of themodulator can be generated with the SDToolbox.At the same time,the zeros and poles ofthe nosie transfer and feedforward feedback factor,are optimized to get the parameters ofeach module of the modulator. Finally,according to the indexes of bandgap voltagereference,fully differential operational amplifier, comparator, switch capacitor structuredesign optimization and simulation, circuit design have been accomplished.