Signal Processing and Integrated Circuits

Hussein Baher

• Publisher: Wiley
• Year: 2012
• Print ISBN: 9780470710265
• eBook ISBN: 9781119942689
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Signals & Signal Processing
• Index: Technology & Engineering

This book provides a balanced account of analog, digital and mixed-mode signal processing with applications in telecommunications. Part I Perspective gives an overview of the areas of Systems on a Chip (Soc) and mobile communication which are used to demonstrate the complementary relationship between analog and digital systems. Part II Analog (continuous-time) and Digital Signal Processing contains both fundamental and advanced analysis, and design techniques, of analog and digital systems. This includes analog and digital filter design; fast Fourier transform (FFT) algorithms; stochastic signals; linear estimation and adaptive filters. Part III Analog MOS Integrated Circuits for Signal Processing covers basic MOS transistor operation and fabrication through to the design of complex integrated circuits such as high performance Op Amps, Operational Transconductance Amplifiers (OTA's) and G m -C circuits. Part IV Switched-capacitor and Mixed-mode Signal Processing outlines the design of switched-capacitor filters, and concludes with sigma-delta data converters as an extensive application of analog and digital signal processing

• Contains the fundamentals and advanced techniques of continuous-time and discrete-time signal processing.
• Presents in detail the design of analog MOS integrated circuits for signal processing, with application to the design of switched-capacitor filters.
• Uses the comprehensive design of integrated sigma-delta data converters to illustrate and unify the techniques of signal processing.
• Includes solved examples, end of chapter problems and MATLAB® throughout the book, to help readers understand the mathematical complexities of signal processing.

The treatment of the topic is at the senior undergraduate to graduate and professional levels, with sufficient introductory material for the book to be used as a self-contained reference.

Part I

Perspective

‘Science as it exists at present is partly agreeable, partly disagreeable. It is agreeable through the power which it gives us of manipulating our environment, and to a small but important minority, it is agreeable because it affords intellectual satisfaction. It is disagreeable because, however we may seek to disguise the fact, it assumes a determinism which involves, theoretically, the power of predicting human actions; in this respect, it seems to lessen human power.’

Bertrand Russell ‘Is Science Superstitious?’ (in ‘Sceptical Essays’)

Chapter 1

Analog, Digital and Mixed-mode Signal Processing

1.1 Digital Signal Processing

The widespread use of digital signal processing systems is due to many factors including reliability, reproducibility, high precision, freedom from aging and temperature effects, low cost and efficient computational algorithms. Furthermore, the revolution in the microelectronics field [1–3] has been characterized by a continuous increase in the level of integration leading to complete systems being integrated on a single chip, that is, systems on a chip (SoC) [3–5].

1.2 Moore's Law and the “Cleverness” Factor

The integrated circuit dates back to around 1960. Since then, the number of devices on a chip has increased dramatically in line with an observation [1, 2] predicting a doubling every year. Now, millions of transistors can be manufactured on a single chip allowing phenomenal processing capability. If we define a pixel as the smallest spot on a chip that can be controlled in the fabrication process, then this will determine the contribution of device miniaturization and chip area to the content of the chip. This contribution can be measured by the quantity A/S where A is the chip area and S is the pixel area. As progress continued, it was found that the number of devices on a chip was actually increasing faster than A/S. This additional growth was a result of “clever” techniques of exploiting the space on the chip. These include forming thin-film capacitors on the side holes etched into a chip instead of on the surface, and self-aligned structures where part of the device is used as the mask in the fabrication process. Next came the effect of the wiring on limiting the size of the chip. This, again, has been tackled [1] by the “cleverness” of increasing the number of wire layers.

1.3 System on a Chip

Such a system comprises application specific integrated circuits (ASICs). Examples are the single-chip TV or the single chip camera, and the ever-emerging new generations of integrated telecommunication systems particularly in the mobile communication area. Such systems include analog and digital sections on the same chip where the technology of choice has been CMOS and possibly BiCMOS. Most functions on these chips are implemented using digital signal processing circuits. However, analog circuits are needed as an interface between the system and the real world which is, of course, analog in nature. Figure 1.1 shows a typical SoC containing embedded digital signal processors, embedded memory, reconfigurable logic, and analog circuits to interface with the analog continuous-time world.

Figure 1.1 System on a chip (SoC)

The design of signal processing systems with low-power requirements is one of the most important areas of research [6, 7] which together with the need for high speed and density of integration have led to great advances in technology and clever circuit design methods [8].

1.4 Analog and Mixed-mode Signal Processing

The trend to replace, for example, analog filters by digital filters is understandable in view of the advantages of digital filters. However, there are some functions on the processor which will always remain analog [4]. These are the following:

a. At the input of the system, signals from a sensor, microphone, antenna or cable must be received, amplified and filtered, that is processed and brought to a level that permits digitization with acceptable signal to noise ratio and low distortion. Here, we need low-noise amplifiers (LNAs), variable gain amplifiers (VGAs), filters, oscillators and mixers. Applications are:

• Data and biomedical instrumentation.
• Sensor interfaces such as airbags and accelerometers.
• Telecommunications receivers such as telephone or cable modems and wireless telephones.

b. At the output of the system the signal is reconverted from digital to analog form and strengthened so that it can drive an external load such as an antenna or a loudspeaker with low distortion. Here we also need buffers, filters, oscillators and mixers. Applications are the following

• Telecommunications transmitters
• Audio and video, such CD, SACD, DVD and Blueray
• Loudspeakers
• TV
• PC monitors
• Hearing aids

c. Mixed-mode circuits are also needed for the interface between the analog and digital parts. These include sample and hold circuits for the sampling of signals, analog to digital (A/D) converters as well as digital to analog converters for signal reconstruction. These are mixed-mode circuits.

d. The integrated circuits discussed above need stable references for their operation which are analog voltage and current sources and crystal oscillators.

Figure 1.2 illustrates the above points with the block diagram of a mobile telephone/Bluetooth receiver section [9]. This highlights the fact that both analog and digital circuits coexist on the same chip employing CMOS technology, and also the interrelationship between analog and digital signal processing.

Figure 1.2 The analog and digital parts of a mobile telephone/Bluetooth receiver section

1.5 Scope

Now, what do we need to know in order to be able to design a system on a chip? Our knowledge must include the following:

1. Methods of description of both analog and digital signals in the time and frequency domains.

2. Methods of description of the systems which process the signals. We need to do this for both analog and digital systems.

3. Design techniques for analog circuits such as amplifiers, integrators, differentiators, and most importantly: filters taking into account the non-ideal effects.

4. Integrated circuit implementations of analog circuits using CMOS technology.

5. Design of digital filters taking into account the finite word-length effects inherent in all digital processors.

6. Random signals require special methods for their description and processing, leading to the subject of adaptive filters. These, together with the related topics of linear prediction, estimation, and system modelling are essential.

7. Modern design techniques of discrete-time filtering using switched-capacitor techniques, since these are particularly amenable to implementation using VLSI techniques.

8. Design of A/D and D/A converters since these act as the interfaces between the digital and analog parts of the system.

Detailed treatment of the above topics is the aim of this book. To facilitate the numerical calculations, and to be able to study the responses of systems and evaluate their performances, we need a powerful software package. MATLAB® is a good choice, and it is used throughout the book.

Part II

Analog (Continuous-time) and Digital Signal Processing

‘It is very desirable in instruction, not merely to persuade the student of the accuracy of important theorems, but to persuade him in the way which itself has, of all possible ways, the most beauty.’

Bertrand Russell ‘The Study of M...

Table of contents

• Cover
• Quotes
• Title Page
• Copyright
• Dedication
• About the Author
• Preface
• Part I: Perspective
• Part II: Analog (Continuous-time) and Digital Signal Processing
• Part III: Analog MOS Integrated Circuits for Signal Processing
• Part IV: Switched-capacitor and Mixed-mode Signal Processing
• Answers to Selected Problems
• Index