Preface xiii
MATLAB, and some both. The repetitive type of problem was avoided. Some of the problems explore issues
not covered in the text but related to it. The MATLAB problems were designed so that a better understanding
of the theoretical concepts is attained by the student working them out.
- We feel two additional features would be beneficial to students. One is the inclusion of quotations and
footnotes to present interesting ideas or historical comments, and the other is the inclusion of sidebars that
attempt to teach historical or technical information that students should be aware of. The theory of signals
and systems clearly connects with mathematics and a great number of mathematicians have contributed to
it. Likewise, there is a large number of engineers who have contributed significantly to the development and
application of signals and systems. All of them need to be recognized for their contributions, and we should
learn from their experiences.
- Finally, other features are: (1) the design of the index of the book so that it can be used by students to find
definitions, symbols, and MATLAB functions used in the text; and (2) a list of references to the material.
CONTENT
The core of the material is presented in the second and third part of the book. The second part of the book
covers the basics of continuous-time signals and systems and illustrates their application. Because the concepts
of signals and systems are relatively new to students, we provide an extensive and complete presentation of these
topics in Chapters 1 and 2. The presentation in Chapter 1 goes from a very general characterization of signals
to very specific classes that will be used in the rest of the book. One of the aims is to familiarize students with
continuous-time as well as discrete-time signals so as to avoid confusion in their processing later on—a common
difficulty encountered by students. Chapter 1 initiates the representation of signals in terms of basic signals that
will be easily processed later with the transform methods. Chapter 2 introduces the general concept of systems,
in particular continuous-time systems. The concepts of linearity, time invariance, causality, and stability are
introduced in this chapter, trying as much as possible to use the students’ background in circuit theory. Using
linearity and time invariance, the computation of the output of a continuous-time system using the convolution
integral is introduced and illustrated with relatively simple examples. More complex examples are treated with
the Laplace transform in the following chapter.
Chapter 3 covers the basics of the Laplace transform and its application in the analysis of continuous-time
signals and systems. It introduces the student to the concept of poles and zeros, damping and frequency, and
their connection with the signal as a function of time. This chapter emphasizes the solution of differential
equations representing linear time-invariant (LTI) systems, paying special attention to transient solutions due
to their importance in control, as well as to steady-state solutions due to their importance in filtering and in
communications. The convolution integral is dealt with in time and using the Laplace transform to emphasize
the operational power of the transform. The important concept of transfer function for LTI systems and the
significance of its poles and zeros are studied in detail. Different approaches are considered in computing the
inverse Laplace transform, including MATLAB methods.
Fourier analysis of continuous-time signals and systems is covered in detail in Chapters 4 and 5. The Fourier
series analysis of periodic signals, covered in Chapter 4, is extended to the analysis of aperiodic signals resulting
in the Fourier transform of Chapter 5. The Fourier transform is useful in representing both periodic and aperi-
odic signals. Special attention is given to the connection of these methods with the Laplace transform so that,
whenever possible, known Laplace transforms can be used to compute the Fourier series coefficients and the
Fourier transform—thus avoiding integration but using the concept of the region of convergence. The concept
of frequency, the response of the system (connected to the location of poles and zeros of the transfer function),
and the steady-state response are emphasized in these chapters.
The ordering of the presentation of the Laplace and the Fourier transformations (similar to the Z-transform
and the Fourier representation of discrete-time signals) is significant for learning and teaching of the material.
