adc lecture 1

Introduction

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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 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: OIC Basic Electronics Lab

E-mail: khuhedkk@hotmail.com

*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:

fs2FM

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