Introduction to Digital
signal processing
PREPARED BY – ANURADHA TANDON
ASSISTANT PROFESSOR,
IC BRANCH, EE DEPARTMENT,
IT, NU
outline
1. Introduction
2. Course content
3. Teaching Methodology
4. Evaluation
5. Let’s get started
1. Introduction
 What is signal?
 What is the difference between signal conditioning and
signal processing?
 Need for signal processing
 Types of processing
 Difference between analog and digital signal processing
 Digital v/s. analog signal processing
What is signal?
Anything which carries information
Examples are –
- speech, is encountered in telephony, radio, and everyday life
- biomedical signals, (heart signals, brain signals)
- Sound and music, as reproduced by the compact disc player
- Video and image,
- Radar signals, which are used to determine the range and
bearing of distant targets
Cont.….
WHAT IS SIGNAL?
In this course we shall adopt the following definition for the
signal:
“a signal is defined as any physical quantity that varies
with time, space or any other independent variable or
variables” (Proakis and Manolakis)
Cont.….
WHAT IS THE DIFFERENCE BETWEEN SIGNAL
CONDITIONING AND SIGNAL PROCESSING?
Input
Measurand
Signal
Signal
Sensing
Electrical
Conditioning
Processing
Element
Output
Element
Element
Fig. 1: Elements of Measurement System
Source: NPTEL lecture notes, EE Department, IIT, Kharagpur
Cont.….
WHAT IS THE DIFFERENCE BETWEEN SIGNAL
CONDITIONING AND SIGNAL PROCESSING?
A signal conditioning element converts one type of
electronic signal into another type of signal.
Its primary use is to convert a signal that may be difficult to
read by conventional instrumentation into a more easily
read format.
Source: NPTEL lecture notes, EE Department, IIT, Kharagpur
Cont.….
WHAT IS THE DIFFERENCE BETWEEN SIGNAL
CONDITIONING AND SIGNAL PROCESSING?
In performing this conversion a number of functions may take
place.
They include:
◦ Amplification
◦ Electrical Isolation
◦ Linearization
◦ Cold junction compensation
◦ Excitation
Source: (http://www.omega.com/prodinfo/SignalConditioners.html)
Cont.….
WHAT IS THE DIFFERENCE BETWEEN SIGNAL
CONDITIONING AND SIGNAL PROCESSING?
Signal processing is the challenge of extracting useful
information from signals or more formally,
Signal processing is the analysis, interpretation, and
manipulation of signals like sound, images, time-varying
measurement values and sensor data etc…
For example biological data such as electrocardiograms,
control system signals, telecommunication transmission
signals such as radio signals, and many others.
Cont.….
Need for signal processing
When a signal is transmitted from one point to another
there is every possibility of contamination /deformation of
the signal by external noise. So to retrieve the original
signal at the receiver suitable filters are to be used, i.e.,
the signal is processed to obtain the pure signal.
Or in general, the processing of the signal helps to estimate
characteristic parameters of the signal and also to
transform the signal in to the desired form.
Types of processing
◦ Transformation
◦ Filtering
◦ Detection
◦ Estimation
◦ Recognition and classification
◦ Coding (compression)
◦ Synthesis and reproduction
◦ Recording, archiving
◦ Analyzing, modeling
Categories of signal processing
Depending on whether the signal is analog or digital, signal
processing is categorized as analog signal processing and digital
signal processing.
So, let’s first understand the analog and the digital signals.
Analog and digital signal
Analog signal processing
Analog signal processing if for signals that have not been digitized,
as in classical radio, telephone, radar, and television systems.
This involves linear electronic circuits such as passive filters, active
filters, additive mixers, integrators and delay lines.
It also involves non-linear circuits such as compander, multiplicators
(frequency mixers and voltage-controlled amplifiers), voltagecontrolled filters, voltage-controlled oscillators and phase-locked
loops.
Digital signal processing
Digital signal processing — for signals that have been digitized,
processing is done by general-purpose computers or by digital
circuits such as ASICs, field-programmable gate arrays or specialized
digital signal processors (DSP chips).
Cont.….
Digital Signal Processing
Digital Signal in
Digital
Processing
Digital Signal out
Operation, Transformation performed
on digital signals (using a computer or
other special-purpose digital hardware)
Cont.….
Digital Signal Processing
But what about analog signals?
ADC
x
Digital sampling of
an analog signal:
A
DSP
Y
DAC
Example of DSP algorithms is
MAC:

ai
i = 1
count
t
Y =
* xi
for (i = 1; i < count; i++){
sum += m[i] * n[i]; }
Cont.….
Digital And analog Processing system
example
x(n) and y(n)
are discrete
signals
v(t) and vo(t)
are continuous
signals
What is Special about Signal Processing
Applications?
Large number of samples being continuously fed to the system
(samples or blocks).
Repetitive Operations:
◦ The same operation being applied to different set of samples
◦ Parallel processing
Vector and Matrix Operations
Real time operations
Digital v/s. analog signal processing
Discussion on Advantages of DSP
• Accuracy:
The analog circuits are prone to temperature and
external effects, but the digital filters have no such problems.
• Flexibility:
Reconfiguration of analog filters is very complex
whereas the digital filters can be reconfigured easily by changing
the program coefficients.
• Storage: Digital signals can be easily stored on any magnetic media
or optical media are using semiconductor chips.
CONT….
Discussion on Advantages of DSP
• Easy operation: Even complex mathematical operations can be
performed easily using computers, which is not the case with
analog processing.
• Multiplexing: Digital signal processing provides the way for
Integrated service digital network (ISDN) where digitized signals can
be multiplexed with other digital data and transmitted through the
same channel.
DSPing: Aim & Tools
Application Areas
Image Processing
Instrumentation/Control Speech/Audio
Military
Pattern recognition
spectrum analysis
speech recognition
secure communications
Robotic vision
noise reduction
speech synthesis
radar processing
Image enhancement
data compression
text to speech
sonar processing
Facsimile
position and rate
digital audio
missile guidance
animation
control
equalization
Application Areas
Telecommunications
Biomedical
Consumer applications
Echo cancellation
patient monitoring
cellular mobile phones
Adaptive equalization
scanners
UMTS
ADPCM trans-coders
EEG brain mappers
digital television
Spread spectrum
ECG Analysis
digital cameras
Video conferencing
X-Ray storage/enhancement
internet phone etc.
DSP Techniques that will be Covered in
the Course
 Digital filtering for cleaning a signal from noise
 Discrete Fourier transforms for finding a particular frequency
component
 Correlation techniques to find a signal buried in noise
 Communications especially for filtering out noise
Course Content
Signals & systems:
Introduction, classification of signals, Classification of discrete time signals and
systems (energy signal & power signals), (periodic & nonperiodic), (even & odd
signal), static & dynamic system, shift variant & invariant systems, linear & nonlinear, causal & noncausal, stable & unstable systems, non-recursive & recursive,
FIR & IIR systems, linear convolution, cross correlation & auto correlation.
Analysis of signals:
Fourier transform of discrete time signals, FT of standard signal & properties of
FT, IFT Discrete Fourier Transform, Definition of DFT & IDFT, DFT of standard
signals, properties of DFT, applications of DFT, FFT Algorithms, Introduction,
properties of Wn, classification, Radix-2, FFT algorithm, Circular convolution
CONT……..
Course Content
Analysis of LTI systems:
ADC, sampling process, anti filter, quantization, Z- transform, properties of ZTransform, Inverse ZTransform, Response of LT in Z domain with pole-zero
representation, Stability & causality in terms of Z-transform.
Digital filters:
Difference between analog & digital filters, types of Digital filters, Design of FIR
filters, Design of IIR filters, In comparison of IIR & FIR filters.
CONT……..
Reference Books
1. Digital Signal Processing : Principles, Algorithms and Applications
by J.G. Proakis and D.G. Manolakis
2. Digital Signal Processing by S. Salivahanan, A. Vallavaraj & C.
Gnanapriya
Teaching Scheme
4 credit course
3 lectures/ week
2 hours lab/ week
2 class tests
1 mid-semester examination
Evaluation
• Term Paper is to be written as a part of special assignment (in group
of 2 students only)
•Term paper topics will be uploaded by August 15, 2014 on the
course blog
• The weightage of each component will be uploaded on the course
website soon.
• The course blog is 2ic401at.wordpress.com
• You will receive the invitation to follow the blog very soon.
References
www.ti.com
www.analog.com
www.dspguru.com
www.mathworks.com
www.dsptutor.freeuk.com
www.dspguide.com
www.elsevier.com/locate/dsp (On line journal)
 dsp.rice.edu (rice university)
 www.youtube.com (lecture on DSP)
Lecture notes of Dr.Y. Narasimha Murthy Ph.D, Reader, Department of Physics & Electronics
CONT……
Concluding Remarks
The woods are lovely, dark and deep,
But I have promises to keep,
And miles to go before I sleep,
And miles to go before I sleep.
---- Robert Frost
GOOD LUCK!