Understanding Digital Signal Processing (2nd Edition) - page 6

Preface

This book is an expansion of the original Understanding Digital Signal Processing textbook published in 1997 and, like the first edition, its goal is to help beginners understand this relatively new technology of digital signal processing (DSP). Additions to this second edition include:

• Expansion and clarification of selected spectrum analysis and digital filtering topics covered in the first edition making that material more valuable to the DSP beginner.

• Expanded coverage of quadrature (complex I/Q) signals. In many cases we used three-dimension time and frequency plots to enhance the description of, and give physical meaning to, these two-dimensional signals.

• With the new emphasis on quadrature signals, material was added describing the Hilbert transform and how it's used in practice to generate quadrature signals.

• Discussions of Frequency Sampling, Interpolated FIR, and CIC filters; giving these important filters greater exposure than they've received in past DSP textbooks .

• A significant expansion of the popular "Digital Signal Processing Tricks" chapter.

• Revision of the terminology making it more consistent with the modern day language of DSP.

It's traditional at this point in the preface of a DSP textbook for the author to tell readers why they should learn DSP. I don't need to tell you how important DSP is in our modern engineering world, you already know that. I'll just say that the future of electronics is DSP, and with this book you will not be left behind.

LEARNING DIGITAL SIGNAL PROCESSING

Learning the fundamentals, and how to speak the language, of digital signal processing does not require profound analytical skills or an extensive background in mathematics. All you need is a little experience with elementary algebra, knowledge of what a sinewave is, this book, and enthusiasm . This may sound hard to believe, particularly if you've just flipped through the pages of this book and seen figures and equations that look rather complicated. The content here, you say, looks suspiciously like the material in technical journals and textbooks that, in the past, have successfully resisted your attempts to understand. Well, this is not just another book on digital signal processing.

This book's goal is to gently provide explanation followed by illustration, not so that you may understand the material, but that you must understand the material. ^{[ ]} Remember the first time you saw two people playing chess? The game probably appeared to be mysterious and confusing. As you now know, no individual chess move is complicated. Given a little patience, the various chess moves are easy to learn. The game's complexity comes from deciding what combinations of moves to make and when to make them. So it is with understanding digital signal processing. First we learn the fundamental rules and processes, and then practice using them in combination.

^{[ ]} "Here we have the opportunity of expounding more clearly what has already been said" (Rene Descartes, 1596–1650).

If learning digital signal processing is so easy, then why does the subject have the reputation of being hard to understand? The answer lies partially in how the material is typically presented in the literature. It's difficult to convey technical information, with its mathematical subtleties, in written form. It's one thing to write equations, but it's another matter altogether to explain what those equations really mean from a practical standpoint, and that's the goal of this book.

Too often, written explanation of digital signal processing theory appears in one of two forms: either mathematical miracles occur and the reader is simply given a short and sweet equation without further explanation, or the reader is engulfed in a flood of complex variable equations and phrases such as "it is obvious that," and "with judicious application of the homogeneity property." In their defense, authors usually do provide the needed information, but too often the reader must figuratively grab a pick and shovel, put on a miner's helmet, and try to dig the information out of a mountain of mathematical expressions. (This book presents the results of several fruitful mining expeditions.) How many times have you followed the derivation of an equation, after which the author states they're going to illustrate that equation with an example—which turns out to be just another equation? Although mathematics is necessary to describe digital signal processing, I've tried to avoid overwhelming the reader with math because a recipe for technical writing that's too rich in equations is hard for the beginner to digest.

The intent of this book is expressed by a popular quote from E.B. White in the introduction of his Elements of Style (Macmillan Publishing, New York, 1959):

"Will (Strunk) felt that the reader was in serious trouble most of the time, a man floundering in a swamp, and that it was the duty of anyone attempting to write English to drain the swamp quickly and get his man up on dry ground, or at least throw him a rope."

I've attempted to avoid the traditional instructor-student relationship, but rather to make reading this book like talking to a friend while walking in the park. I've used just enough mathematics to develop a fundamental understanding of the theory, and then illustrate that theory with practical examples.