Design And Research Of Σ-△ Adc's Digital Decimation Filter

Based on the advantages of high-resolution,good linearity and easy to integrated with digital system,∑-△ADC is being widely applied in the audio and electron measurement fields. As an important and necessary component of∑-△ADC, digital decimation filter is the key design of high performance∑-△ADC.With basic principle and structure of∑-△ADC, this paper presents significant research on the design theory and methods, and proposes a 5-stage multi-sample-rate digital decimation filter: Cascaded Integrator Comb(CIC) Filter+CIC Compensator+2-stage Halfband Decimator+DC Compensator.The proposed design introduced CSD coding, MAG , RAG, Distributed Arithmetic and synchronous pipeline to optimize the decimation filter module, to simplify the functional structure, to promote the filtering efficiency, to boost the working speed, to improve the performance and to reduce the implementation needed hardware resources.The implemented device's typical parameters are 18-bits resolution, 256 downsampling ratio, 44kHz bandwidth, 98dB dynamic range, 96dB SNR and 0.05dB passband ripple.Having been velidated by effecitive and low-cost FPGA simulation and Simulink's behavior verification, the whole design has relized a proper trade-off on working speed, power dissipation and hardware resources, the function and performance come up to the expected requirements.