tailieunhanh - 05 Analog-to-Digital Conversion Architectures

Digital signal processing methods fundamentally require that signals are quantized at discrete time instances and represented as a sequence ofwords consisting of 1’s and 0’s. | Kosonocky S. Xiao P. Analog-to-Digital Conversion Architectures Digital Signal Processing Handbook Ed. Vijay K. Madisetti and Douglas B. Williams Boca Raton CRC Press LLC 1999 1999 by CRC Press LLC Analog-to-Digital Conversion Architectures Stephen Kosonocky IBM Corporation TJ. Watson Research Center Peter Xiao NeoParadigm Labs Inc. Introduction Fundamentals of A D and D A Conversion Nonideal A D and D A Converters Digital-to-Analog Converter Architecture Analog-to-Digital Converter Architectures Flash A D Successive Approximation A D Converter Pipelined A D Converter Cyclic A D Converter Delta-Sigma Oversampling Converter Delta-Sigma A D Converter Architecture References Introduction Digital signal processing methods fundamentally require that signals are quantized at discrete time instances and represented as a sequence of words consisting of 1 s and 0 s. In nature signals are usually nonquantized and continuously varied with time. Natural signals such as air pressure waves as a result of speech are converted by a transducer to a proportional analog electrical signal. Consequently it is necessary to perform a conversion of the analog electrical signal to a digital representation or vice versa if an analog output is desired. The number of quantization levels used to represent the analog signal and the rate at which it is sampled is a function of the desired accuracy bandwidth that is required and the cost of the system. Figure shows the basic elements of a digital signal processing system. The analog signal is first converted to a discrete time signal by a sample and hold circuit. The FIGURE Digital signal processing system. output of the sample and hold is then applied to an analog-to-digital converter A D circuit where the sampled analog signal is converted to a digitally coded signal. The digital signal is then applied to 1999 by CRC Press LLC the digital signal processing DSP system where the desired DSP algorithm is performed.