Optimal Design Of Modulators For Oversampled Converters

Oversampled A/D converters have become very popular in recent years. Some of their advantages include relaxed requirements for anti-alias filters, relaxed requirements for component matching, high resolution and compatibility with digital VLSI technology. There is a significant amount of literature discussing the principle, theory and implementation of various oversampled converters. Such converters are likely to continue to proliferate in the foreseeable future. Additionally, more recently there has been great interest in low voltage and low power circuit design. New design techniques have been proposed for both the digital domain and the analog domain. Both trends point to the importance of the low-power design of oversampled A/D converters. Unfortunately, there has been no systematic study of the optimal design of modulators for oversampled converters. Design has generally focused on new architectures with little attention being paid to optimization. The goal of Design of Modulators for Oversampled Converters is to develop a methodology for the optimal design of modulators in oversampled converters. The primary focus of the presentation is on minimizing power consumption and understanding and limiting the nonlinearities that result in such converters. Design of Modulators for Oversampled Converters offers a quantitative justification for the various design tradeoffs and serves as a guide for designing low-power highly linear oversampled converters. Design of Modulators for Oversampled Converters will serve as a valuable guide for circuit design practitioners, university researchers and graduate students who are interested in this fast-moving area.

Switched-Current Design and Implementation of Oversampling A/D Converters discusses the switched-current (SI) technique and its application in oversampling A/D converters design. The SI technique is an analog sampled-data technique that fully exploits the digital CMOS process. Compared with the traditional switched-capacitor (SC) technique, the SI technique has both pros and cons that are highlighted in the book. With the consideration of similarity and difference of SI and SC techniques, oversampling A/D converter architectures are tailored and optimized for SI design and implementation in the book. Switched-Current Design and Implementation of Oversampling A/D Converters emphasizes the practical aspects of SI circuits without tedious mathematical derivations, and is full of circuit design and implementation examples. There are more than 10 different chips included in the book, demonstrating the high-speed (over 100 MHz) and ultra-low-voltage (1.2 V) operation of SI circuits and systems in standard digital CMOS processes. Therefore, the book is of special value as a practical guide for designing SI circuits and SI oversampling A/D converters. Switched-Current Design and Implementation of Oversampling A/D Converters serves as an excellent reference for analog designers, especially A/D converter designers, and is of interest to digital designers for real-time signal processing who need A/D interfaces. The book may also be used as a text for advanced courses on the subject.

This now famous anthology brings together various aspects of oversampling methods and compares and evaluates design approaches. It describes the theoretical analysis of converter performances, the actual design of converters and their simulation, circuit implementations, and applications.

Oversampled Delta-Sigma Modulators: Analysis, Applications, and Novel Topologies presents theorems and their mathematical proofs for the exact analysis of the quantization noise in delta-sigma modulators. Extensive mathematical equations are included throughout the book to analyze both single-stage and multi-stage architectures. It has been proved that appropriately set initial conditions generate tone free output, provided that the modulator order is at least three. These results are applied to the design of a Fractional-N PLL frequency synthesizer to produce spurious free RF waveforms. Furthermore, the book also presents time-interleaved topologies to increase the conversion bandwidth of delta-sigma modulators. The topologies have been generalized for any interleaving number and modulator order. The book is full of design and analysis techniques and contains sufficient detail that enables readers with little background in the subject to easily follow the material in it.

The interest for :I:~ modulation-based NO converters has significantly increased in the last years. The reason for that is twofold. On the one hand, unlike other converters that need accurate building blocks to obtain high res olution, :I:~ converters show low sensitivity to the imperfections of their building blocks. This is achieved through extensive use of digital signal pro cessing - a desirable feature regarding the implementation of NO interfaces in mainstream CMOS technologies which are better suited for implementing fast, dense, digital circuits than accurate analog circuits. On the other hand, the number of applications with industrial interest has also grown. In fact, starting from the earliest in the audio band, today we can find :I:~ converters in a large variety of NO interfaces, ranging from instrumentation to commu nications. These advances have been supported by a number of research works that have lead to a considerably large amount of published papers and books cov ering different sub-topics: from purely theoretical aspects to architecture and circuit optimization. However, so much material is often difficultly digested by those unexperienced designers who have been committed to developing a :I:~ converter, mainly because there is a lack of methodology. In our view, a clear methodology is necessary in :I:~ modulator design because all related tasks are rather hard.

Among analog-to-digital converters, the delta-sigma modulator has cornered the market on high to very high resolution converters at moderate speeds, with typical applications such as digital audio and instrumentation. Interest has recently increased in delta-sigma circuits built with a continuous-time loop filter rather than the more common switched-capacitor approach. Continuous-time delta-sigma modulators offer less noisy virtual ground nodes at the input, inherent protection against signal aliasing, and the potential to use a physical rather than an electrical integrator in the first stage for novel applications like accelerometers and magnetic flux sensors. More significantly, they relax settling time restrictions so that modulator clock rates can be raised. This opens the possibility of wideband (1 MHz or more) converters, possibly for use in radio applications at an intermediate frequency so that one or more stages of mixing might be done in the digital domain. Continuous-Time Delta-Sigma Modulators for High-Speed A/D Conversion: Theory, Practice and Fundamental Performance Limits covers all aspects of continuous-time delta-sigma modulator design, with particular emphasis on design for high clock speeds. The authors explain the ideal design of such modulators in terms of the well-understood discrete-time modulator design problem and provide design examples in Matlab. They also cover commonly-encountered non-idealities in continuous-time modulators and how they degrade performance, plus a wealth of material on the main problems (feedback path delays, clock jitter, and quantizer metastability) in very high-speed designs and how to avoid them. They also give a concrete design procedure for a real high-speed circuit which illustrates the tradeoffs in the selection of key parameters. Detailed circuit diagrams, simulation results and test results for an integrated continuous-time 4 GHz band-pass modulator for A/D conversion of 1 GHz analog signals are also presented. Continuous-Time Delta-Sigma Modulators for High-Speed A/D Conversion: Theory, Practice and Fundamental Performance Limits concludes with some promising modulator architectures and a list of the challenges that remain in this exciting field.

A comprehensive overview of Sigma-Delta Analog-to-Digital Converters (ADCs) and a practical guide to their design in nano-scale CMOS for optimal performance. This book presents a systematic and comprehensive compilation of sigma-delta converter operating principles, the new advances in architectures and circuits, design methodologies and practical considerations − going from system-level specifications to silicon integration, packaging and measurements, with emphasis on nanometer CMOS implementation. The book emphasizes practical design issues – from high-level behavioural modelling in MATLAB/SIMULINK, to circuit-level implementation in Cadence Design FrameWork II. As well as being a comprehensive reference to the theory, the book is also unique in that it gives special importance on practical issues, giving a detailed description of the different steps that constitute the whole design flow of sigma-delta ADCs. The book begins with an introductory survey of sigma-delta modulators, their fundamentals architectures and synthesis methods covered in Chapter 1. In Chapter 2, the effect of main circuit error mechanisms is analysed, providing the necessary understanding of the main practical issues affecting the performance of sigma-delta modulators. The knowledge derived from the first two chapters is presented in the book as an essential part of the systematic top-down/bottom-up synthesis methodology of sigma-delta modulators described in Chapter 3, where a time-domain behavioural simulator named SIMSIDES is described and applied to the high-level design and verification of sigma-delta ADCs. Chapter 4 moves farther down from system-level to the circuit and physical level, providing a number of design recommendations and practical recipes to complete the design flow of sigma-delta modulators. To conclude the book, Chapter 5 gives an overview of the state-of-the-art sigma-delta ADCs, which are exhaustively analysed in order to extract practical design guidelines and to identify the incoming trends, design challenges as well as practical solutions proposed by cutting-edge designs. Offers a complete survey of sigma-delta modulator architectures from fundamentals to state-of-the art topologies, considering both switched-capacitor and continuous-time circuit implementations Gives a systematic analysis and practical design guide of sigma-delta modulators, from a top-down/bottom-up perspective, including mathematical models and analytical procedures, behavioural modeling in MATLAB/SIMULINK, macromodeling, and circuit-level implementation in Cadence Design FrameWork II, chip prototyping, and experimental characterization. Systematic compilation of cutting-edge sigma-delta modulators Complete description of SIMSIDES, a time-domain behavioural simulator implemented in MATLAB/SIMULINK Plenty of examples, case studies, and simulation test benches, covering the different stages of the design flow of sigma-delta modulators A number of electronic resources, including SIMSIDES, the statistical data used in the state-of-the-art survey, as well as many design examples and test benches are hosted on a companion website Essential reading for Researchers and electronics engineering practitioners interested in the design of high-performance data converters integrated in nanometer CMOS technologies; mixed-signal designers.

This book presents the study, design, modulation, optimization and implementation of low power, passive DT-ΣΔMs for use in audio applications. The high gain and bandwidth amplifier normally used for integration in ΣΔ modulation, is replaced by passive, switched-capacitor branches working under the Ultra Incomplete Settling (UIS) condition, leading to a reduction of the consumed power. The authors describe a design process that uses high level models and an optimization process based in genetic algorithms to achieve the desired performance.