Upload
shahzad-khalid-ch
View
223
Download
1
Embed Size (px)
Citation preview
8/2/2019 Advance Communication System Lectures Part 1
1/36
8/2/2019 Advance Communication System Lectures Part 1
2/36
Text Book: Electronic Communication Systemby Kennedy and Davis
Reference Text: Modern Digital and AnalogCommunication System by B.P. Lathi
(Soft/photo copy will be provided)
8/2/2019 Advance Communication System Lectures Part 1
3/36
Explain the principles of a communicationsystems
Discuss the nature of information, different typesof signals involved and their characteristics
Make the distinction between Analog and Digitalcommunication systems
Determine the need of modulation anddifferentiate various type of modulation
techniques in time, frequency domain Important steps in analog to digital conversion,
PCM, PAM, PPM etc
8/2/2019 Advance Communication System Lectures Part 1
4/36
Basic Communication System (Chp 1 Kennedy)
Concept of time and frequency domain
Different types of Signals (Chp 2 Reference)
Baseband vs Passband Communication
Modulation and its needs (Chp 1 Kennedy)
8/2/2019 Advance Communication System Lectures Part 1
5/36
5
How do you want to senddata/information tosomeone who is far from
you?
8/2/2019 Advance Communication System Lectures Part 1
6/36
6
Communication : To transfer information from one place toanother
8/2/2019 Advance Communication System Lectures Part 1
7/36
7
1837 Samuel Morse invented telegraph. 1858 First telegraph cable across Atlantic (Canada Ireland) 1876 Alexander Graham Bell invented telephone. 1988 Heinrich Hertz introduce electromagnetic field theory. 1897 Marconi invented wireless telegraph. 1906 Radio communication system was invented. 1923 Television was invented. 1938 Radar and microwave system was invented for World War II. 1950 TDM was invented. 1956 First telephone cable was installed across Atlantic. 1960 Laser was invented 1962 Satellite communication 1969 Internet DARPA 1970 Corning Glass invented optical fiber. 1975 Digital telephone was introduced. 1985 Facsimile machine. 1988 Installation of fiber optic cable across Pacific and Atlantic. 1990 World Wide Web and Digital Communication. 1998 Digital Television.
8/2/2019 Advance Communication System Lectures Part 1
8/368
The Real AimIf the information that you want to send is your voice, how tomake sure that what you are saying is understood by your friend?
Basic Parts of a Communication System
8/2/2019 Advance Communication System Lectures Part 1
9/369
TransmitterTransmissionMedium
ReceiverInputTransducer
OutputTransducer
Noise
wired / wireless
mtx(t)
s(t) r(t)
ptx(t)
n(t)
mrx(t)prx(t)
s(t) Input signal; audio, video, image, data etc.
mtx(t) Modulating signal; input signal that has been converted to electrical
signal.ptx(t) Modulated signal transmit by the transmitter.
n(t) Noise signal.
prx(t) Modulated signal receive by the receiver.
mrx(t) Modulating signal at the receiver.
r(t) Output signal.
8/2/2019 Advance Communication System Lectures Part 1
10/36
8/2/2019 Advance Communication System Lectures Part 1
11/36
11
Input Transducer convert input signal, s(t) in electrical forms. eg:microphone.Transmitter involve modulation process convert modulatingsignal,mtx(t) to modulated signal,ptx(t). And finally transmit thesignal.Transmission medium connecting the transmitter and the receiverthat enable the modulated signal,ptx(t) propagate through themedium.Receiver receive the modulated signal,prx(t) and then convert thesignal to modulating signal,mrx(t) through the process calleddemodulation.Output Transducer convert the modulating signal,mrx(t) to itsoriginal forms (output signal), r(t) that is useful to the users. eg:loud speaker.
8/2/2019 Advance Communication System Lectures Part 1
12/36
12
Twisted pair Unshielded Twisted Pair (UTP) Shielded Twisted Pair (STP)Coaxial
Fiber Optic
Waveguide
8/2/2019 Advance Communication System Lectures Part 1
13/36
100 Mbps is how many bits per sec?Which is bigger:10,000 Mbps, 0.01Tbps or 10Gbps?
Wireless channel capacity:
8/2/2019 Advance Communication System Lectures Part 1
14/36
Data(nonelectrical)
ElectricalWaveform
Without any shift in the range of frequencies of the signalThe signal is in its original form, not changed by modulation.
Basebandis the original information that is to be Sent.
It starts from zero and to some specific frequency
WHAT IS BASEBAND ?
8/2/2019 Advance Communication System Lectures Part 1
15/36
After modulation, the original baseband
signal is moved to a range of frequency whichfar more higher than the baseband signal
So its a range of frequency shifted aftermodulation
8/2/2019 Advance Communication System Lectures Part 1
16/36
MODULATION IS THE PROCESS OFCHANGING SOME PROPERTYOF THEINFORMATION SOURCES INTO SUITABLEFORM FOR TRANSMISSION THROUGH THEPHISICAL MEDIUM/CHANNEL
Process of coverting baseband signal intopassband signal is called modulationIt is performed in the Transmitter bya device calledModulator.
16
8/2/2019 Advance Communication System Lectures Part 1
17/36
Transmitter
Carrier
Information tobe transmitted
(Baseband signal)
Transmitted
signal
Channel
Received
signal
Receiver
Recovery ofinformation
8/2/2019 Advance Communication System Lectures Part 1
18/36
18
8/2/2019 Advance Communication System Lectures Part 1
19/36
Amplitude Modulation (AM)Frequency Modulation (FM)Phase Modulation (PM)
19
8/2/2019 Advance Communication System Lectures Part 1
20/36
20
8/2/2019 Advance Communication System Lectures Part 1
21/36
Channel assignment (various informationsources are not always suitable for directtransmission over a given channel)Efficient Utilization of bandwidth andmultiplexingReduce noise &interferenceReduction in antenna size
21
8/2/2019 Advance Communication System Lectures Part 1
22/36
DEMODULATION IS THE REVERSE PROCESSOF MODULATION BY CONVERTING THEMODULATED INFORMATION SOURCES BACKTO ITS ORIGINAL INFORMATION (ITREMOVES THE INFORMATION FROM THECARRIER SIGNAL).
It is performed in the Receiver bya device calledDemodulator.22
8/2/2019 Advance Communication System Lectures Part 1
23/36
IT CONSISTS OF ALL FREQUENCIESCONTAINED IN THE WAVEFORM ANDTHEIR RESPECTIVE AMPLITUDE IN THEFREQUENCY DOMAIN.
23
8/2/2019 Advance Communication System Lectures Part 1
24/36
24
100MH
z
WaveguideCoaxial CableTwisted PairCable
Infrared
Visible
Ultraviolet
Optical Fiber
ExtraHigh
Frequency
EHF
SuperHigh
Frequency
SHF
UltraHigh
Frequency
UHF
VeryHigh
Frequency
VHF
High
Frequency
HF
Medium
Frequency
MF
Low
Frequency
LFVery
Low
Frequency
VLF
Audio
Line-of-sightradio
Skywaveradio
Groundwaveradio
Wavelength
Frequencydesignations
Transmissionmedia
Propagationmodes
Representativeapplications
Frequency
Laser beam
100km 10km 1km 100m 10m 1m 10cm 1cm 10-6m
Tele
phone
Tele
graph
Mobilradio
VHFTVandFM
Mobiland
Aeronautical
UHFTV
CBradio
Ama
teurradio
AMbroadcasting
Aerona
utical
Submarinecable
Navigation
Transoc
eanicradio
Broadband
PCS
Wirelesscommunication
Cellular,Pager
Satellite-satellite
Microwaverelay
Earth-satellite
Radar
Widebanddata
1kHz
10kHz
100kHz
1MHz
10MHz
1GHz
10GHz
1G0Hz
1014Hz
1015Hz
8/2/2019 Advance Communication System Lectures Part 1
25/36
8/2/2019 Advance Communication System Lectures Part 1
26/36
IT IS THE DIFFERENCE BETWEEN THEHIGHEST FREQUENCIES AND THE LOWESTFREQUENCIES OF THE INPUT SIGNALFREQUENCIES (fB = 2fm ). The bandwidth of a communication signal bandwidth of the information signal.
26
8/2/2019 Advance Communication System Lectures Part 1
27/36
If human voice frequencies containsignals between 300 Hz and 3000 Hz,
a voice frequency channel should havebandwidth equal or greater than 2700Hz. a communication channel cannot propagate asignal that contains a frequency that ischanging at a rate greater than the ChannelBandwidth.
27
8/2/2019 Advance Communication System Lectures Part 1
28/36
Lecture 27 28
Signal
SourceModulator
Power
Amplifier
Antenna
8/2/2019 Advance Communication System Lectures Part 1
29/36
Block diagram In Modulator the audio modulates the RF
amplitude
ModulatorLow-pass
filter
AFamplifier
Microphone
RF
oscillator
Power
amplifier
8/2/2019 Advance Communication System Lectures Part 1
30/36
Lecture 27 30
The modulator converts the frequency of theinput signal from the audio range (0-5kHz) tothe carrier frequency of the station (i.e..
605kHz-615kHz)
frequency5kHz
Frequency domainrepresentation of input
Frequency domainrepresentation of output
frequency610kHz
8/2/2019 Advance Communication System Lectures Part 1
31/36
Lecture 27 31
RF
Amplifier
IF
Mixer
IF
Amplifier
Envelope
Detector
Audio
Amplifier
Antenna
Speaker
8/2/2019 Advance Communication System Lectures Part 1
32/36
8/2/2019 Advance Communication System Lectures Part 1
33/36
A signal g(t) in the intervalt1tt1+T0 can be represented by
1
000 )sin()cos()(n
nn tnbtnaatg 011 Tttt
01
1
)(1
0
0
Tt
t
dttgT
a
01
1
)cos()(2
0
0
Tt
t
n dttntgT
a
01
1
)sin()(2
0
0
Tt
t
n dttntgT
b T0 = 2 /0
8/2/2019 Advance Communication System Lectures Part 1
34/36
Or, in the compact form
Ifg(t) is even then bn = 0 for all n
Ifg(t) is odd then an=0 for all n.
1
00 )cos()(
n
nn tnCCtg
;22
nnn baC
n
nn
a
b1tan
011 Tttt
C0 = a0 ;
8/2/2019 Advance Communication System Lectures Part 1
35/36
The frequency 0= 2/T0 is called thefundamental frequency and the multiple of thisfrequency n0 is called the nth harmonic.
FS ofg(t) is equal to g(t) over the interval t1tt1+T0 only.
The FS for all tis a periodic function of periodT0 in which the segment ofg(t) over the intervalt1tt1+T0 repeats periodically.
If the function g(t) itself is periodic with periodT0 then the FS represents g(t) for all t.
8/2/2019 Advance Communication System Lectures Part 1
36/36
Dn is related to Cn and n as
| Dn | is called the amplitude spectrum of the signal.
Dn is called the phase spectrum of the signal.They provide a frequency-domainrepresentation of the
signal.
)0(
000)(
nn
tjn
n
n
tjn
n eDDeDtg
dtetg
T
DT
tjn
n
0
0)(1
0
nnn CDD2
1||||
011Tttt
nnnDD