2 Practical MATLAB® Applications for Engineers
To a physician, it may be
- An electrocardiogram (EKG)
- An electroencephalogram (EEG)
- A sonogram
For a telecommunication engineer, it
may be - Audio sound wave (human voice or music)
- Video (TV, HDTV, teleconference, etc.)
- Computer data
- Modulated-waves (amplitude modulation [AM],
frequency modulation [FM], phase modula-
tion [PM], quadrature amplitude modulation
[QAM], etc.) - Multiplexed waves (time division multiplex-
ing [TDM], statistical time division multiplex-
ing [STDM], frequency division multiplexing
[FDM], etc.)
From a block box diagram point of view, signals constitute inputs to a system, and their
responses referred to as outputs. Since many of the measuring, recording, tracking, and
processing instruments of signal activities are electrical or electronic devices, scientists
and engineers usually convert any type of physical variations into an electrical signal.
Electrical signals can be classifi ed using a variety of criteria. Some of the signal’s clas-
sifi cation criteria are
a. Signals may be functions of one or more than one independent variable generated
by a single source or multiple sources.
b. Signals may be single or multidimensional.
c. Signals may be orthogonal or nonorthogonal, periodic or nonperiodic, even, odd,
or present a particular symmetry.
d. Signals may be deterministic or nondeterministic (probabilistic).
e. Signals may be analog or discrete.
f. Signals may be narrow or wide band.
g. Signals may be power or energy signals.
In any case, signals are produced as a result of a process defi ned by a mathematical relation
usually in the form of an equation, an algorithm, a model, a table, a plot, or a given rule.
A one-dimensional (1-D) signal is given by a mathematical expression consisting of one
independent variable, for example, audio. A 2-D signal is a function of two independent
variables, for example, a black and white picture. A full motion black and white video can
be viewed as a 3-D signal, consisting of pictures (2-D) that are transmitted or processed at
a particular rate. The dimension of a video signal can be increased by adding color (red,
green, and blue), luminance, etc.
Deterministic and probabilistic signals is another broad way to classify signals. Deter-
ministic signals are those signals where each value is unique, while nondeterministic
signals are those whose values are not specifi ed. They may be random or defi ned by statis-
tical values such as noise. In this book, the majority of the signals are restricted to 1-D and
2-D, limited to one independent variable usually either time (t) or frequency (f or w), and