### 基本信息

- 原书名：Structure and Interpretation of Signals and Systems
- 原出版社： Addison Wesley/Pearson

### 编辑推荐

Signals and systems；Defining signals and systems；State machines；Complsing state machines；Linear systems；Hybrid systems；Frequency domain；Frequency response；Filtering；The four Fourier transforms；Sampling and reconstruction；Stability；Laplace and Z transforms；Composition and feedback control。

### 内容简介

通信书籍

“这部著作的确展现了信号与系统在当前研究和应用范围内的核心地位。”

——Ravi Mazumdar，普度大学

“Lee和Varaiya在富有建设性的重大课程改革中迈出了大胆的一步。他们采用了革命性的方法，而不是逐步改动，这也正是我们所需要的。”

——Theodore Djaferis，马萨诸塞大学

“这部著作是相关主题中最好的，它在内容和表述风格上都是革命性的。”

——Ratnesh Kumar，肯塔墓队学

本书结合加州大学伯克利分校多年成功授课的经验而编写，对信号与系统进行了深刻与清晰的剖析，力求反映当今数字化世界的成果。所用实例包含声音和图像处理，取代以前的枯燥电路，从而激发读者的兴趣去了解应用背后的理论知识。

本书的配套Web站点(WWW．aw.com／lee_varaiya)包括扩充的实验材料，可帮助读者跨越理论与实践之间的障碍。另外，还提供了更多内容，包括声音和图像交互式操作的Java小程序，帮助读者更加直观地理解书中内容。

本书适合作为电子工程、计算机工程。计算机科学等专业的教材。

### 作译者

Pravin Varaiya于加州大学伯克利分校获得博士学位，目前是该校电子工程与计算机科学系Nortel网络客座教授。因研究控制与通信网络。转置。混合系统等而闻名。他是IEEE会员和美国国家工程学院成员。所得荣誉有Guggenheim Fellowship、Miller Research Professorship、图卢兹国立理工学院的名誉博士头衔以及IEEE控制系统协会的Technical Field奖。

### 目录

1 Signals and systems 1

1.1 Signals 2

1.1.1 Audio signals 3

PROBING FURTHER: Household electrical

power 7

1.1.2 Images 9

1.1.3 Video signals 11

PROBING FURTHER: Color and light 12

1.1.4 Signals representing physical

attributes 15

1.1.5 Sequences 16

1.1.6 Discrete signals and sampling 18

1.2 Systems 23

1.2.1 Systems as functions 24

1.2.2 Telecommunications systems 25

PROBING FURTHER: Wireless

communication 27

PROBING FURTHER:LEO telephony 28

PROBING FURTHER: Encrypted speech 32

### 前言

How else could microelectromechanical systems 0VIEMS) become so important in EE? Is this not mechanical engineering? Or signal processing? Is this not mathematics? Or digital networking? ls this not computer science? How is it that control system techniques are profitably applied to aeronautical systems, structural mechanics, electrical systems, and options pricing?

This book approaches signals and systems from a computational point of view. It is intended for students interested in the modern, highly digital problems of electrical engineering, computer science, and computer engineering. In particular, the approach is applicable to problems in computer networking, wireless communication systems, embedded control, audio and video signal processing,and, of course, circuits.

A more traditional introduction to signals and systems would be biased toward the latter application, circuits. It would focus almost exclusively on linear time-invariant systems, and would develop continuous-time models first, with discrete-time models then treated as an advanced topic. The discipline, after all,grew out of the context of circuit analysis. But it has changed. Even pure EE graduates are more likely to write software than to push electrons, and yet we

still recognize them as electrical engineers.

The approach in this book benefits students by showing from the start that the methods of signals and systems are applicable to software systems, and most interestingly, to systems that mix computers with physical devices such as circuits, mechanical control systems, and physical media. Such systems have become pervasive, and profoundly affect our daily lives.

The shift away from circuits implies some changes in the way the method-ology of signals and systems is presented. While it is still true that a voltage that varies over time is a signal, so is a packet sequence on a network. This text de-fines signals to cover both. While it is still true that an RLC circuit is a system, so is a computer program for decoding Internet audio. This text defines systems to cover both. While for some systems the state is still captured adequately by variables in a differential equation, for many it is now the values in registers and memory of a computer. This text defines state to cover both.

The fundamental limits also change. Although we still face thermal noise and the speed of light, we are likely to encounter other limits--such as complexity, computability, chaos, and, most commonly, limits imposed by other human constructions---before we get to these. A voiceband data modem, for example, uses the telephone network, which was designed to carry voice, and offers as immutable limits such nonphysical constraints as its 3 kHz bandwidth. This has

no intrinsic origin in the physics of the network; it is put there by engineers.

Similarly, computer-based audio systems face latency and jitter imposed by the operating system. This text focuses on composition of systems so that the limits imposed by one system on another can be understood.

The mathematical basis for the discipline also changes. Although we still use calculus and differential equations, we frequently need discrete math, set theory, and mathematical logic. Whereas the mathematics of calculus and differential equations evolved to describe the physical world, the world we face as system designers often has nonphysical properties that are not such a good match for this mathematics. This text bases the entire study on a highly adaptable formalism

rooted in elementary set theory.

Despite these fundamental changes in the medium with which we operate,the methodology of signals and systems remains robust and powerful. It is the methodology, not the medium, that defines the field.

The book is based on a course at Berkeley taught over the past four years to more than 2,000 students in electrical engineering and computer sciences. That experience is reflected in certain distinguished features of this book. First, no background in electrical engineering or computer science is assumed. Readers should have some exposure to calculus, elementary set theory,series, first-order linear differential equations, trigonometry, and elementary complex numbers.

The appendices review set theory and complex numbers, so this background is less essential.

Approach This book is about mathematical modeling and analysis of signals and systems,

applications of these methods, and the connection between mathematical models and computational realizations. We develop three themes. The first theme is the use of sets and functions as a universal language to describe diverse signals and systems. Signals--voice, images, bit sequences--are represented as functions with an appropriate domain and range. Systems are represented as functions whose domain and range are themselves sets of signals. Thus, for exam-

ple, a modem is represented as a function that maps bit sequences into voice-like signals.

The second theme is that complex systems are constructed by connecting simpler subsystems in standard ways--cascade, parallel, and feedback. The connections detennine the behavior of the interconnected system from the behaviors of component subsystems. The connections place consistency requirements on the input and output signals of the systems being connected.

Our third theme is to relate the declarative view (mathematical, "what is")with the imperative view (procedural, "how to"). That is, we associate mathematical analysis of systems with realizations of these systems. This is the heart of engineering. When EE was entirely about circuits, this Was relatively easy,because it was the physics of the circuits that was being described by the mathematics. Today we have to somehow associate the mathematical analysis with