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2013 Edition, May 2013

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Active, Most Current

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ISBN: 9781119979258
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Product Details:

  • Revision: 2013 Edition, May 2013
  • Published Date: May 2013
  • Status: Active, Most Current
  • Document Language:
  • Published By: John Wiley and Sons (WILEY)
  • Page Count: 426
  • ANSI Approved: No
  • DoD Adopted: No

Description / Abstract:


Sigma-Delta modulators (ΣΔMs) have become one of the best choices for the implementation of analog/digital interfaces integrated in CMOS technologies. Compared to other kinds of analog-to-digital converters (ADCs), ΣΔMs cover the widest conversion region of the resolution-versus-bandwidth plane, being the most efficient solution to digitize very diverse types of signals in an increasing number of application scenarios, which span from high-resolution low-bandwidth data conversion (like digital audio, sensor interfaces, and instrumentation) to ultra-low power biomedical systems and medium-resolution broadband wireless communications. This versatility, together with their robustness and their simplicity in many practical situations, has motivated that more and more engineers today consider ΣΔMs as a first choice for their research projects and their industrial products.

The first idea underlying the operation of ΣΔMs was patented by Cutler in 1960 [1], although its application to the construction of data converters was first reported in the published literature by Inose et al in 1962 [2]. The operation of ΣΔMs is relatively simple to describe, although sometimes difficult to analyze. Essentially, the fundamental principle behind ΣΔMs is based on the combination of two signal processing techniques, namely oversampling and quantization noise shaping. The former consists of taking the signal samples at a higher rate than the one dictated by the Nyquist sampling theorem. These samples are commonly quantized with a large error by using a low-resolution quantizer. The resulting oversampled quantization error is filtered in the modulator feedback loop, so that its frequency spectrum is shaped in such a way that a large portion of its power is pushed out of the signal band, where it is removed by a digital filter. The outcome of the combined action of oversampling and noise shaping allows ΣΔMs to achieve a highprecision digitization by using a low-resolution coarse quantizer. Therefore, unlike other kinds of ADC architectures that require high-precision analog circuits, ΣΔMs trade the accuracy of their analog circuitry by the speed of digital signal processing, thus achieving a higher degree of insensitivity to circuit error mechanisms and potentially benefiting from CMOS technology evolution towards the nanometer scale.