signal processor

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1.1 What is a Signal
We are all immersed in a sea of signals. All of us from the smallest living
unit, a cell, to the most complex living organism(humans) are all time time
receiving signals and are processing them. Survival of any living organism
depends upon processing the signals appropriately. What is signal? To define
this precisely is a difficult task. Anything which carries information is a signal.
In this course we will learn some of the mathematical representations of
the signals, which has been found very useful in making information processing
systems. Examples of signals are human voice, chirping of birds, smoke
signals, gestures (sign language), fragrances of the flowers. Many of our body
functions are regulated by chemical signals, blind people use sense of touch.
Bees communicate by their dancing pattern.Some examples of modern high
speed signals are the voltage charger in a telephone wire, the electromagnetic
field emanating from a transmitting antenna,variation of light intensity in an
optical fiber. Thus we see that there is an almost endless variety of signals
and a large number of ways in which signals are carried from on place to
another place.


What is signal processing
By processing we mean operating in some fashion on a signal to extract some
useful information. For example when we hear same thing we use our ears
and auditory path ways in the brain to extract the information. The signal
is processed by a system. In the example mentioned above the system is
biological in nature. We can use an electronic system to try to mimic this
behavior. The signal processor may be an electronic system, a mechanical
system or even it might be a computer program.
The word digital in digital signal processing means that the processing is
done either by a digital hardware or by a digital computer.



Analog versus digital signal processing
The signal processing operations involved in many applications like communication
systems, control systems, instrumentation, biomedical signal processing
etc can be implemented in two different ways
(1) Analog or continuous time method and
(2) Digital or discrete time method.
The analog approach to signal processing was dominant for many years. The
analog signal processing uses analog circuit elements such as resistors, capacitors,
transistors, diodes etc. With the advent of digital computer and
later microprocessor, the digital signal processing has become dominant now
a days.