Design Of Modulator And Its Extraction Filter For 16-bitsigma Delta ADC

In the current society that emphasizes more and more on personalization,the comfort of sensory experience is increasingly valued.The public’s demand in the audio field is gradually increasing,pursuing better signal-to-noise ratio and higher dynamic range to meet the user’s high quality music appreciation experience.In order to study the analog-to-digital converter suitable for high quality audio chips,a 16-bit Sigma Delta modulator and its digital extraction filter are designed in this paper.The main research contents are as follows:1.A Sigma Delta modulator with a single-loop,2nd-order,1-bit quantization feedback structure is proposed.Firstly,according to the design requirement of audio signal bandwidth and signal-to-noise ratio greater than 98 d B,the structure of the modulator with 256 times oversampling,2nd order with 1bit quantization is determined through theoretical analysis and in-depth study.Secondly,Simulink design of the modulator under ideal conditions was completed based on the MATLAB SD Toolbox.The advantages of the single-loop,discrete time and feedback structure used in this paper were comprehensively analyzed,and some possible non-ideal factors in the actual circuit were systematically discussed.Finally,according to the parameters and structure of the modulator system model,the circuit design of the modulator and the layout design of the key circuits are completed.The simulation results of the modulator circuit show that the output signal-to-noise distortion ratio is 103 d B and the effective bit count is 16.81 bits.2.A three-stage cascaded digital filter structure of CIC filter,compensation filter and half-band filter is proposed.Based on MATLAB filter Designer platform to complete the design and simulation of the three filters.In this paper,the following improvements are made:firstly,the extractor in the CIC filter is put into the differential filter to reduce the delay and power consumption;secondly,for the design of the compensation filter,the single input signal path is decomposed into two branches by using the multiple decomposition technique in order to reduce the hardware resource consumption;finally,the coefficient symmetry principle of the finite pulse filter is used to combine the same tap coefficients in the halfband filter to reduce the amount of operations.Compared with the conventional filter structure,the filter designed in this paper has the advantages of simple circuit structure and low power consumption under the premise of completing 256-fold drop sampling and filtering3.In this paper,the circuit design of the Sigma Delta modulator circuit is completed based on SMIC 0.18 um process,and the design and simulation of the downsampling filter are completed based on MATLAB platform.The modulator circuit and the extracted filter are simulated as a whole,and the output signal-to-noise distortion ratio is 100.9d B and the effective bit count is 16.47 bits,which meets the design requirements.