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Introduction
ADC ES & BM MUET 1
Course Description
• Title of Subject : Analog & Digital Communication
• Disciplines : Electronic Engineering
• Term : (6th Term)
• Effective : 09ES-Batch and onwards
• Pre-requisites : - Co-requisite: -
• Assessment :
• Sessional Work: 20% Written Examination: 80%
• Marks : Theory: 100 Practical: 50
• Credit Hours : 4 2
• Minimum Contact
• Hours : 52 26
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Sessional Work
• ?? Quizzes
• ?? Assignments
• 2 Class tests
(Aims & objectives of this course + recommended books available on the website: http://www.muet.edu.pk/departments/electronics-engineering/course-outline)
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About me
Khuhed Memon
(Lecturer Dept of ES & BM MUET)
• MS Signal Processing (Nanyang Technological University, Singapore)
• BE Electronics (Pakistan Navy Engineering College, National University of Sciences & Technology, Pakistan)
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Class style
Interactive:
Discussions + questions in class, email, office…..
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Contact Info:
• Office: LEADERS @ IT Building
• E-mail: [email protected]
*best way to communicate : e-mail
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Enjoy the course
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This lecture
• Concept of Signal Processing• Introduction to Signals• Classification of Signals• Basic elements of SP System• Analog to Digital Conversion
– Sampling – Quantization
• Nyquist Theorem• Applications of Signal Processing
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Signal Processing
• Representation, transformation, manipulation of signals and the information they contain.
• Classification:
Depends upon the type of signal to be processed.
• Analog Signal Processing
• Digital Signal Processing
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Signal Processing
• Analog SP
Continuous time signals are processed.
• Digital SP
Discrete - time discrete - valued signals processed by digital computers or other data processing machines.
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Signal??
• Any indication / information
• A change in which some information is residing
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Classification of Signals
• Continuous-time / Discrete-time Signals
• Continuous-valued / Discrete-valued Signals
• Deterministic / Random Signals
• One-dimensional / Multi-dimensional Signals
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Fundamental SP system
• Most signals – Analog in nature.
• Analog to Digital Converter is used as an interface between analog signal and Digital Signal Processor.
A/D Converter D/A ConverterDigital Signal
Processor
Analog
Input Signal
Analog
Output Signal
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A-D Conversion
1. Sampling• First step in going from analog to digital.• In signal processing, sampling is the
reduction of a continuous signal to a discrete signal. A common example is the conversion of a sound wave (a continuous-time signal) to a sequence of samples (a discrete-time signal).
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Sampling
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Nyquist Theorem
• In order the samples represent correctly the analog signal, the sampling frequency must be greater than twice the maximum frequency of the analog signal:
• fs≥2FM
• The limiting frequency 2FM is called Nyquist rate.
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Aliasing (Time Domain)
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Aliasing (Frequency Domain)
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Methods of avoiding Aliasing
• To avoid aliasing, there are two approaches: One is to raise the sampling frequency to satisfy the sampling theorem.The other is to filter off the unnecessary high-frequency components from the continuous-time signal. We limit the signal frequency by an effective low-pass filter, called anti-aliasing prefilter, so that the highest frequency left in the signal is less than half of the intended sampling rate.
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General DSP System
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Quantization
• Slide 143 CCN module 2• MIT OCW
Companding or Non-linear Encoding
• Companding = compressing + expanding
• Why companding?
• Quantization levels not evenly spaced
• Reduces overall signal distortion
• Can also be done by companding
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Applications of SP
• RADAR• SONAR• Medical• Image Processing
– Pattern recognition– Edge detection
• Audio Signal Processing– Speech generation– Speech recognition– Speaker identification
• Telecommunications– Multiplexing– Compression– Echo control