This is the Term paper on analogue and digital signal

1. INTRODUCTION TO INFORMATION THEORY
AND APPLICATIONS
2014
LOVELY
PROFESSIONAL
UNIVERSITY
SUBMITTED BY SUBMITTED TO
NAME :- BIKASH THAPA
ROLL NO :- A55
SECTION :- 1407
GROUP :- 1
COURSE :- BSC.IT
REG NO :- 11413230
“TRANSFORMING EDUCATION TRASNSFORMING INDIA”

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2
Acknowledgement
It was really an awesome experience to be a participant in writing term
paper. I really enjoyed using my own earned skilled and experience in
the class as well as book study to accomplish the term paper topic. As
can as I can do I have done my all the best and I am hoping it will bring
satisfactory result.
In the course of being involved in writing term
paper, I got lots of help and support from my teachers, colleagues and all
my friends. So I can’t remain without thanking them for their seen and
unseen help so I would like to thanks all of them. I also owe to those
authors whose books proved to be a milestone to me to accomplish the
term paper.
At last I like to thanks my parents for their great support to
complete my term paper and let me to study BSc.IT (information
technology) in Lovely Professional University.
Bikash Thapa

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Table of Contents
1.1 Analog signal ...........................................................................................5
1.2 Digital signal............................................................................................9
1.3 Difference between digital and analog signal.....................................12
Abstract

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ANALOG AND DIGITAL SIGNAL

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Signal:
A signal is defined as a function of one or more variables
which conveys information on the nature of a physical phenomenon. The
value of the function can be a real valued scalar quantity, a complex
valued quantity, or perhaps a vector.
System:
A system is defined as an entity that manipulates one or
more signals to accomplish a function, thereby yielding new signals.
Continuous-time signal:
A signal x (t) is said to be a continuous time
signal if it is defined for all time t.
Discrete-time signal:
A discrete time signal x [nT] has values
specified only at discrete points in time.
Signal processing:
A system characterized by the type of
operation that it performs on the signal. For example, if the operation is
linear, the system is called linear. If the operation is non-linear, the
system is said to be non-linear, and so forth. Such operations are usually
referred to as “Signal Processing”
1.1 Analog signal
An analog or analogue signal is any continuous signal for

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which the time varying feature (variable) of the signal is a representation
of some other time varying quantity, i.e., analog to another time varying
signal. For example, in an analog audio signal, the
instantaneous voltage of the signal varies continuously with
the pressure of the sound waves. It differs from a digital signal, in which
a continuous quantity is represented by a discrete function which can
only take on one of a finite number of values. The term analog signal
usually refers to electrical signals; however, mechanical, hydraulic, and
other systems may also convey analog signals.
An analog signal uses some property of the medium to convey the
signal's information. For example, an aneroid barometer uses rotary
position as the signal to convey pressure information. In an electrical
signal, the voltage, current, or frequency of the signal may be varied to
represent the information.
Any information may be conveyed by an analog signal; often such a
signal is a measured response to changes in physical phenomena, such
as sound, light, temperature, position, or pressure. The physical variable
is converted to an analog signal by a transducer. For example, in sound
recording, fluctuations in air pressure (that is to say, sound) strike the
diaphragm of a microphone which induces corresponding fluctuations in
the current produced by a coil in an electromagnetic microphone, or the
voltage produced by a condenser microphone. The voltage or the current
is said to be an "analog" of the sound.
An analog signal has a theoretically infinite resolution. In practice an
analog signal is subject to electronic noise and distortion introduced
by communication channels and signal processing operations, which can
progressively degrade the signal-to-noise ratio. In contrast, digital
signals have a finite resolution. Converting an analog signal to digital
form introduces a constant low-level noise called quantization noise into
the signal which determines the noise floor, but once in digital form the
signal can in general be processed or transmitted without introducing
additional noise or distortion. Therefore as analog signal processing
systems become more complex, they may ultimately degrade signal

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resolution to such an extent that their performance is surpassed by digital
systems. This explains the widespread use of digital signals in
preference to analog in modern technology. In analog systems, it is
difficult to detect when such degradation occurs. However, in digital
systems, degradation can not only be detected but can be corrected as
well.
Example of Analog Signals:
 An analog signal can be any time-varying signal.
 Minimum and maximum values can be either positive or negative.
 They can be periodic (repeating) or non-periodic.
 Sine waves and square waves are two common analog signals.
 Note that this square wave is not a digital signal because its
minimum value is negative.
 Video and Audio
Fig: analog signal
Analog transmission:

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 Transmit analog signals without regard to content.
 Attenuation limits length of transmission link
 Cascaded amplifiers boost signals energy for longer distances but
cause distortion
 Analog data can tolerate distortion.
 Introduces errors in digital data.
Pros and Cons of Analog Signals:
Advantages:
 Major advantages of the analog signal is infinite amount of data.
 Density is much higher.
 Easy processing.
Disadvantages:
 Unwanted noise in recording.
 If we transmit data at long distance then unwanted disturbance is
there.
 Generation loss is also a big cons of analog signals.
Applications of analog signal are:

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 Thermometer
 Photocopiers
Old land-line telephones
Audio tapes
VCRs (same as TV)
1.2 Digital signal
A digital signal is a physical signal that is a representation of a
sequence of discrete values. The term digital signal can refer to either of
the following:
1. any continuous-time waveform signal used in digital
communication, representing a bit stream or other sequence
of discrete values
2. a pulse train signal that switches between a discrete number of
voltage levels or levels of light intensity, also known as a line
coded signal or baseband transmission, for example a signal found
in digital electronics or in serial communications, or a pulse code
modulation (PCM) representation of a digitized analog signal.
A signal that is generated by means of a digital modulation method
(digital pass band transmission), to be transferred between modems, is in
the first case considered as a digital signal, and in the second case as
converted to an analog signal. In computer architecture and
other digital systems, a waveform that switches between two voltage
levels representing the two states of a Boolean value (0 and 1) is referred
to as a digital signal, even though it is an analog voltage waveform,
since it is interpreted in terms of only two levels.

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Example of Digital signal:
 Digital signal are commonly referred to as square waves or clock
signals.
 Their minimum value must be 0 volts, and their maximum value
must be 5 volts.
 They can be periodic (repeating) or non-periodic.
 The time the signal is high (tH) can vary anywhere from 1% of the
period to 99% of the period.
 Text and Integers.
Digital Signal Transmission:
 Concerned with the content of the signal.
 Attenuation endangers integrity of data.
 Digital signal
Repeaters achieve greater distance.
Repeaters recover the signal and retransmit.
Pros and Cons of Digital Signal

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Advantages:
 Because of their digital nature they can travel faster in over digital
lines.
 Ability to transfer more data as compared to analog.
Disadvantages:
 Greater bandwidth is essential.
 Systems and processing is more complex.
Applications of Digital Signal are:
 PCs, PDAs
 Mobile Phones.
Difference in working:
 The working of the digital signals are more reliable and accurate
because they use the digital media or the numeric method where as
analog signals are based on the small fluctuations.
 Digital signals are used to play that information which is came
from re-sampling, whereas analog are known for playing recorded
data.
 Digital signals have priority over analog signals because with the
help of digital signals users have ability to change the visual and
the audio or re-record it but with analog signals you can do such
parameters.

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1.3 Difference between digital and analog signal
Analog signal
1. It produces a continuous signal.
2. Signal that is continuous in a time
and can assume an infinite number
of values in a given range.
3. It is denoted by sine wave.
4. Analog hardware is not flexible.
5. It Store data in the form of wave
signal.
6. Analog instrument consume more
power.
7. It is of low cost and portable.
For e.g.:- thermometer.
Wave form in analog signal
Digital signal
1. It produce a discrete signal
2. Signal that is continuous in a
time and assumes only a
limited number of values.
3. It is denoted by square wave.
4. Digital hardware is flexible in
implementation
5. It store data in the form of
binary bit.
6. Digital instrument consume
less power.
7. It is expensive and not easily
portable.
For e.g.: computers.
Wave form in digital
signal

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Reference books
1. Digital Signal Processing By.
Sen M. Kuo & Woon-Seng Gan
2. Digital Signal Processing a Practical Approach. By
Emmanuel C. Ifeachor & Barrie W. Jervis
3. Digital Signal Processing Principles, Algorithms and Applications
By:
John G.Proakis & Dimitris G.Manolakis