Design And Realization Of Decimation Filter For 24 Bit ∑-△A/D Converter

With the rapid development of microelectronic technology and the aid of computer technology in IC design and development, the scale and complexity of integrated circuits have been increasing exponentially over the past few decades. Due to its flexibility, high resolution, strong anti-interference and fast increasing processing power, more and more applications are using digital circuits and digital technology. Powerful digital circuits and digital processing technology demand higher performance analog-to-digital converters (ADC), which is the interface between analog and digital worlds. This encouraged research activities on high performance ADCs. Among these high performance ADCs, sigma-delta ADC technology has been proven to be an excellent technology choice for implementing high resolution ADC in large-scale digital CMOS process. Its popularity has made it a critical component in many applications.In this thesis, a brief introduction is given to the application of sigma-delta A/D converters in high-resolution signal processing applications, and the role of decimation filters in sigma-delta A/D converters. The second part explains the basic theory of sigma-delta A/D converters; include the analysis of oversampling and noise shaping technology, followed by a summary of research results in the theory and implementation of digital decimation filters, including comb filters and half-band filter as decimation filters.The sampling frequency of the designed digital decimation filter is 256kHz. The output data rate is 20Hz. The filter's decimation ratio is 12800, with decimation ratio of 3200 realized by the CIC filter and decimation ratio of 4 realized by the half band filter. The CIC filter is implemented using a recursive structure. The half band filter is realized with a transpose structure. Matlab computer software is used in the design and simulations of the filter. The filter is fabricated in CSMC 0.5um CMOS process. The test results verified the filter's functionality. The design goals and targets have been successfully achieved.