Transcript EE521 Analog and Digital Communications

Today some topics will be presented on
the whiteboard. The slides will be
updated on the web site in a few days.
EE521 Analog and
Digital
Communications
James K. Beard, Ph. D.
[email protected]
Tuesday, February 1, 2005
http://astro.temple.edu/~jkbeard/
7/18/2015
Week 2
1
Essentials


Text: Bernard Sklar, Digital Communications,
Second Edition
Prerequisites
 Consent
of Instructor (Dr. Silage)
 SystemView (CD-ROM with text)

Office
 E&A 709
 Hours
TBA, Tuesday afternoons planned
 MWF 10:30 AM to 11:30 AM added
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Week 2
2
Today’s Topics
SystemView
 Signals and Noise
 Detection of Binary Signals
 Inter-symbol interference
 Equalization
 Discussion (as time permits)

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Week 2
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Homework Problem
Sklar Problem 2.4 Page 101
 Given in the files from the CD-ROM

 Basis
of analysis is Fourier series
 Infinite series of pulses in time domain is
infinite series of pulses in frequency domain
(text section 2.4.1.1 pp 63-66)
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Sklar’s Answer
Solution is given as SystemView file
Sum_of_cosines.svu
Number of tokens>10 puts Student version in no-save mode
Fourier transform of train is (Sklar, equations (2.5), (2.6), (2.8)
x(t ) 

   f  k T 
k 
X ( f ) 
1 

TS k 
S

k
f  
TS 

2 
 1  
 2  k  t  
k

    cos 

1
    f  
TS 

 TS  
 TS k 
 TS k  
The issue is that the aux files problem 2.4 appear not to be related to the
textbook problem 2.4.
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The Homework Problem

Basis is



Principle



Natural sampling, 2.4.1.2 pp. 66-68
As opposed to impulse sampling, 2.1.1.1
Sampling replicates system spectra
Distance between replicated spectra is the signal bandwidth
Block diagram of Figure 2.1



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Mixes one of these replicated spectra to baseband
Low pass filters to recover the signal
Problem_2_4.svu
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Formatting and Baseband
Modulation

Topics from Text Chapter 2
 2.5,
Sources of Corruption
 2.6, Pulse Code Modulation
 2.7, Uniform and Non-uniform Quantization
 2.8, Baseband Modulation




Corruption: noise, fading, interference
PCM: Simple digital modulation
Quantization: the ADC and data compression
Baseband modulation: synthesizing the signal
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Sklar Chapter 2
From
other
sources
Information
source
Message
symbols
Source
encode
Format
Essential
Legend:
Optional
Channel
symbols
Encrypt
Channel
encode
Multiplex
Pulse
modulate
gi  t 
ui
Digital
input
mi
Bit
stream
z T 
uˆi
Format
Information
sink
Message
symbols
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Decrypt
Channel
decode
Demultiplex
si  t 
Digital
baseband
waveform
Synchronization
Digital
output
mˆ i
Source
decode
Bandpass
modulate
Detect
Frequency
spread
Digital
bandpass
waveform
X
M
IT
Multiple
access
hc  t 
Channel Channel
impulse
response
r t 
Demodulate &
Sample
Frequency
despread
R
C
V
Multiple
access
To other Channel
destinations symbols
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Spectral Attributes

We are looking for better bandwidth
efficiency
Symbol rate
Bandwidth efficiency 
Bandwidth

Obtained by modulations with
 More
compact spectra
 Less interference between symbols
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M-ary Pulse Modulation

Base modulation types
 Pulse Amplitude
Modulation (PAM)
 Pulse Position Modulation (PPM)
 Pulse Duration Modulation (PDM)

Number of different pulse shapes in a
character is M, hence M-ary modulation
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Baseband Demodulation
and Detection
Signals and noise
 Detection of binary signals in Gaussian
noise
 Inter-symbol interferencie
 Equalization

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Signals and Noise

Base problem is symbol error
 Additive
noise can bridge the difference
between waveforms for different symbols
 Symbol error rate is function of
SNR
 Modulation type


Basic figure of merit is bit energy divided
by noise power spectral density
7/18/2015
Eb
W 
 SNR   
No
R
Week 2
12
Summary
Course overview: we will learn how to
implement critical technologies for digital
communications
 Course is integrated with a follow-on next
semester
 Baseband signals are where we do
modulation == formatting for the channel
 SystemView lets us have most of the
benefits of a lab with minimum time

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Week 2
13
Feedback
Around the room
 Please let me know

 What
your background is
EE
 Design
 SystemView
 Communications

 What
7/18/2015
you expect from this course
Week 2
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Text and Assignment

Text


Benard Sklar, Digital Communicatinons ISBN 0-13-084788-7
SystemView User's Manual, Elanix, Inc



Assignment: Read Text




http://www.elanix.com/
http://www.elanix.com/pdf/SVUGuide.pdf
Chapter 3, 3.1, 3.2, 3.3, 3.4
Load SystemView and examine the samples and demos
Browse appendices of text for review and
supplementary material
Look at TUARC

K3TU, websites


7/18/2015
http://www.temple.edu/ece/tuarc.htm
http://www.temple.edu/k3tu
Week 2
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