From the Inside Flap This textbook presents to undergraduates an introductory explanation of communication systems， with the emphasis on signal design and modulation. The approach is therefore tailored to a careful development of the mathematical principles upon which such systems are based， using examples from a wide variety of current communication systems wherever possible. These range from commercial broadcasting and telephone systems to satellite telemetry and radar. Extended Topical Coverage Material added in this third edition is， primarily， about digital methods and reflects the continually increasing importance of digital signal transmission and modulation in communication systems. New material on the use of fiber optics in communications and the integrated services digital network (ISDN) has been added in Chapter 7， as well as an expended treatment of Nyquist waveform shaping for control of ISI. Optimum filtering methods for use with ISI criteria have been included in Chapter 9. Chapter 10 has an expanded treatment of FSK and both parallel and serial MSK， as well as two new sections on spread spectrum systems. Therefore， the presentation in this last chapter includes digital modulation methods that are currently being investigated for new communication systems designs. Approach and Pedagogical Features Because this textbook is intended for undergraduates， the material is written in as explicit a manner as possible and is clearly and liberally illustrated. Frequent use of example problems (117) and drill problems (133) with answers that， wherever possible， exemplify current practical problems helps to draw the student into an active participation in the learning process. With the example problems worked out in the text， followed by drill problems with answers， this textbook lends itself to self-paced or individualized tutorial instruction. Each chapter ends with a summary section followed by a wide selection of problems so that the instructor can adjust the level considerably by assigning problems appropriate to the level of a specific course. Each of the problems is identified by section number for content; thus students may refer to the appropriate text sections if they encounter difficulties. A major change in this edition is an expanded set of problems for homework assignments at the end of each chapter. The focus of these problems is on analysis， verification， synthesis， extensions， illustrations of practice， and systems design considerations. Because not every problem can incorporate all aspects， there is a wide variety of problems (520 total) in this edition; 60% are new， and nearly 90% are either new or substantially revised from previous editions. It is my hope that these problems will stimulate interest as well as prove very beneficial in understanding the material presented. There are 50 computer problems distributed throughout the book， with the heaviest concentration in Chapter 3 to make use of the DFT and the FFT algorithms. Although programs can be written for many of these problems， they are designed to be run using the engineering software so readily available for personal computers. A unique feature of this third edition is the inclusion of one or two special systems design problems at the end of each chapter. These problems have been taken from practical systems design situations and are intended to not only illustrate the relevance of the material covered but also to give students some concept of what types of problems might arise in engineering work in the area of communication systems. These problems are， by their nature， fairly broad and open-ended; students should learn that in general there is no unique answer but that their work will be judged more on their approach to the problem， taking into account the objectives and using good engineering judgment in the choices made. There is some gradual progression in the level of these problems throughout the book. I recommend that students be encouraged to read the design problems to learn what types of problems some in this area might be working on within just a few years after taking this course. In addition， it is hoped that students will be challenged by such problems and perhaps their interests will be increased in the subject material. Another approach is to have students work in groups on a given design problem， perhaps one of their choosing. In general， there are no unique answers， but some approaches may be better than others， and some may offer better tradeoffs than others. That's what design is all about! Otherwise we are only teaching the mathematics. Audience Basically， the only prerequisites to a course using this textbook are a course in integral calculus and an introductory course in circuit analysis. A course in linear system analysis would be helpful， but it is not essential. Although written primarily for undergraduates in an electrical engineering curriculum， this text could also be used by those in other disciplines， in industry， or in telecommunications practice who are interested in learning， reviewing， and updating their technical background in communication systems. For these groups the chapter arrangements and frequent examples and drill problems make the text appropriate to independent study. Recommended auxiliary reading lists are included in the summary at the end of each chapter. Books in these lists have been carefully selected， and they should be both accessible and readable to undergraduates. They are listed in approximate order of increasing difficulty. References to specific topics are given as footnotes in the text. A majority of the references to periodicals is to the IEEE Communications Magazine， published monthly by the Institute of Electrical and Electronics Engineers and recommended for its excellence in original work， tutorials and survey papers in the area of communication systems. Organization of Text The organization of this textbook is designed to allow maximum flexibility in the choice and presentation of subject matter. If Chapters 2， 3， and 8 constitute review for students， there is sufficient remaining material for a one-semester course. If the material in the early chapters is new to the students， some adjustment may be made by deleting the optional material in each chapter and/or not including the material on probability (Chapter 8). Optional material in each chapter has been designated by a star symbol. Chapter 1 is an introduction to concepts in communication systems and an overview of the book. The Fourier methods of linear systems analysis are reviewed in Chapters 2 and 3， with particular emphasis on what will prove most useful in the succeeding chapters， such as the use of complex notation and interpretations in terms of phasors and spectral representations. These topics are not always brought out in linear systems analysis courses. Material on the numerical computation of Fourier coefficients and the discrete and fast Fourier transforms is widely used for both computational and signal processing applications， and is included as optional material in Chapters 2 and 3. Problems intended to be solved primarily using numerical methods are designed with a prefix check mark in the margin. The material in Chapters 4-7 is an introduction to the principles of communication systems. Chapter 4 covers the topics of correlation， power spectral density and thermal noise. It leads directly into the design of systems based on noise considerations. In fact， one can begin talking about satellite communication systems design considerations already in Chapter 4. Chapters 5-7 cover the topics of amplitude， angle and pulse modulation. This organization of material has been influenced by my teaching this material at the undergraduate level. Students wish to see applications of the mathematical material. To sustain student interest， the more abstract concepts are interspersed with more practical sections that show how the concepts are being used. Thus the presentation begins with an elementary discussion of noise and quickly gets into communication systems， then proceeds through amplitude， angle， and pulse modulation. This avoids having one or two chapters devoted entirely to signal-to-noise calculations - a topic that if prolonged fails to retain student interest at the undergraduate level. The first part of this book does not assume a knowledge of probability theory. Presentation of the basic material without probability helps to keep the emphasis on signal design and modulation. This treatment ends with Chapter 7， and a course taught from a deterministic point of view could end here， or could conclude with some of the material in Chapter 10. For those students for whom the first few chapters are review， there is time in a semester to take up the material in the last three chapters. If students， in addition， have had prior background in probability theory， Chapter 8 can be omitted or used for review. There is ample material in Chapters 9 and 10， in addition to Chapters 4-7， for a one-semester course if the optional sections are covered in each chapter. Chapter 8 is an introduction to the subject of probability and random processes and is presented in such a way that students progress rapidly to the probability-density function and its use in the analysis of communication systems. Chapter 9 builds on this knowledge toward an introduction of such topics as quantization noise and probability of error in baseband transmission. Sections on partial-response signaling， equalization， M-ary signaling， power spectral densities of data waveforms， and coding for reliable communication can be covered if there is time. Chapter 10 is a fairly complete discussion of digital modulation methods， beginning with amplitude-， frequency，- and phase-shift keying and progresses to modern methods of M-ary digital modulation such as quadrature phase-shift keying， minimum-shift keying， and amplitude-phase keying. New sections have been added on spread spectrum systems. The chapter concludes with geometric representations of digital waveforms and an introduction to maximum likelihood detection. After completing Chapter 10 the student will， it is hoped， be interested in taking an advanced course in communication theory that will employ more statistical concepts. The appendixes from the second edition are included in this third edition because instructors found they were useful and readily available references sources. The appendixes on commercial radio and television transmissions have been revised somewhat because of student interest in these topics， and pedagogically， add breadth in background. New sections on stereo television and high definition television have been added. The material in Chapters 4-9 (to Section 9.7)， plus the first four sections of Chapter 10 (but omitting starred sections) has been used for a one-semester course at the University of Wisconsin-Madison at the junior/senior level in electrical engineering. Many of the students in this course are not intending to major in communications but take the course for breadth and because it is recommended for such areas as signal processing， photonics， etc. The remaining material in Chapters 9 and 10 is covered in a succeeding course in communications for majors. Another variation might be to summarize some of the material (e.g.， the signal-to-noise sections) in Chapters 4-7 so that more attention can be given to the material in Chapters 9 and 10. If all the material in the textbook is covered， there is ample material for a two-quarter sequence. Acknowledgments I am indebted to many for their advice and assistance in this third edition. Suggestions and criticisms by reviewers for Addison-Wesley have been most helpful. In particular， I wish to thank Professor S. Hossein Mousavinezhad， Western Michigan University， for his helpful comments， and suggestions for problems in Chapter 9. The comments and reviews of Professors Joseph L. LoCicero， Illinois Institute of Technology， Sunwon Park， Texas A & I University， and Wesley W. Shelton， Jr.， Florida Institute of Technology， were instructive and useful. I express my thanks to Don Fowley and Tom Robbins at Addison-Wesley for their support and encouragement to write this third edition. I appreciate the comments and suggestions made by graduate students that have improved the accuracy and clarity of the text， and for working through some advanced versions of my design problems. Also， I wish to thank Professors W. P. Birkemeier， J.A. Buckew， and B.E.A. Saleh of the University of Wisconsin， and Mr. W.C. Luplow， Executive Director of Electronic Systems R&D， Zenith Electronics Corp.， for their comments and suggestions on specific portions of the text changes and additions. The encouragement of Professor J.L. Shohet， Chairman of the Department of Electrical and Computer Engineering， is sincerely appreciated. My appreciation is extended also to those who were so helpful in two previous editions of this textbook. Finally I express my thanks for the constructive feedback and support of my students. Your comments and fresh insights continue to amaze me， and make teaching so enjoyable. Madison， Wisconsin F.G.S. December 1989Solutions to most problems designed as computer problems have been run on a personal computer using the student version of MathCAD (available from the publisher). --This text refers to the Paperback edition. From the Back Cover This text presents a throrough introduction to communication systems， with and emphasis on engineering aspects of signal waveform design and modulation. Its presentation skillfully connects development of mathematical principles to examples from current operating communication systems. Most importantly， explanations and exercises are carefully motivated with practical applications. Features Explanations of practical communication systems presented in the context of theory. Over 300 excellent illustrations help students visualize difficult concepts and demonstrate practical applications. Over 120 worked-out examples promote mastery of new concepts， plus over 130 drill problems with answers extend these principles. A wide variety of problems， all new to this edition -- including realistic applications， computer-based problems， and design problems. Coverage of current topics of interest， such as fiber optics， spread spectrum systems and Integrated Digital Services Networks. --This text refers to the Paperback edition.