w1. ch 01 sattelite communication
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6-Nov-13 2
Agenda
Taaruf
Textbooks
Course content
Assessment and Grading
How to communicate
Q&A
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Taaruf
Assoc. Dr. Rashid A. Saeed Room No. : Room 6
HP : 0961343660
E-mail: [email protected] [email protected]
Facebook: Rashid Abdelhaleem Saeed
Lecture time: 4.00 7.00pm
Tutorial:
Consultation hour: per appointment
mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected] -
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Textbook(s)
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Assessment and Grading
Method %
Mid-term Examination 30
Final Examination 40
Assignments/Projects/Presentations 20
Quizzes 10
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Ch 1:Overview of Satellite Systems
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Wireless Classification
Wireless system, definition is connectingbetween two point without the use ofwired connection. This can be
accomplished by: Sonic
Infrared
Optical Radio frequency
acoustic
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Wireless Classificationcontd
Another way to categorize wirelesssystem as:
Point-to-point (PTP)
Remote control, microwave link, etc
Point-to-multipoint (PMP)
AM and FM broadcast radio and TV,
LMDS: uses in TV broadcast and internet access,i.e. WiMAX
Multipoint-to-multipoint (MTM)
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What is the different between point-to-point andpeer to peer
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Wireless Communication Systems Today
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Intelsat 10 at 68.5 E Africa footprint.
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Telestar 12 footprint
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NileSat footprint
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Advantages of Satellites
The advantages of satellite communicationover terrestrial communication are: The coverage area of a satellite greatly
exceeds that of a terrestrial system. Transmission cost of a satellite is independent
of the distance from the center of the coveragearea.
Satellite to Satellite communication is veryprecise.
Higher Bandwidths are available for use.
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Disadvantages of Satellites
Launching satellites into orbit is costly.
Satellite bandwidth is gradually becoming
used up. There is a larger propagation delay in satellite
communication than in terrestrialcommunication.
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Satellite-Related Terms
Earth Stations
antenna systems on or near earth
Uplink transmission from an earth station to a
satellite
Downlink
transmission from a satellite to an earthstation
Transponderelectronics in the satellite that convert
uplink signals to downlink signals
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Satellite System Elements
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Space Segment
Satellite
TT&C Ground Station
Ground Segment
Earth Stations
CoverageRegion
SCC
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Satellite Subsystems
Communications Antennas
Transponders
Common Subsystem (Bus Subsystem) Telemetry/Command (TT&C)
Satellite Control (antenna pointing,attitude)
Propulsion
Electrical Power
Structure
Thermal Control
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Satellite Services
Fixed Service Satellites (FSS) Example: telephone system, Sat to Cable
Broadcast Service Satellites (BSS) Example: Satellite Television/Radio Also called Direct
Broadcast Service (DBS). In Europe called DTH
Mobile Service Satellites (MSS) Include land mobile, maritime mobile, and aeronautical
mobile. Navigational satellite services i.e. GPS
Meteorological satellite services i.e. Weather andrescue service
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Frequency Bands
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F All ti
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Frequency Allocationsfor Satellite Services
To facilitate frequency planning, the worldis divided into three regions:
Region 1: Europe, Africa
Region 2: North and South America andGreenland
Region 3: Asia, Australia, and the southwest
Pacific
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Frequency Bands
Different kinds of satellites use differentfrequency bands. LBand: 1 to 2 GHz, used by MSS
S-Band: 2 to 4 GHz, used by MSS, NASA, deep space research
C-Band: 4 to 8 GHz, used by FSS the "BUD" (Big Ugly Dish)band
X-Band: 8 to 12.5 GHz, used by FSS and in terrestrial imaging,ex: military and meteorological satellites
Ku-Band:12.5 to 18 GHz: used by FSS and BSS (DBS) There are more than 22 FSS Ku band satellites orbiting over North America,each carrying 12 to 48 transponders,
K-Band: 18 to 26.5 GHz: used by FSS and BSS
Ka-Band: 26.5 to 40 GHz: used by FSS
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Space-Earth Frequency Usability
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Atmospheric attenuation effects for Space-to-Earth as a function of frequency (clear air
conditions). (a) Oxygen; (b) Water vapor. [Source: ITU 1988]
22.2GHz (H20)
53.5-65.2 GHz (Oxygen)
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Satellites orbits
Satellite Orbits
GEO
LEO
MEO
HEO
HAPs
LEO 500 -1000 km
GEO 36,000 km
MEO 5,000 15,000 km
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Geostationary Earth Orbit (GEO)
These satellites are in orbit 35,863 km
Objects in Geostationary orbit revolvearound the earth at the same speed as the
earth rotates.
This means GEO satellites remain in thesame position relative to the surface of
earth. now over 200 active commercial
communications satellites in geostationary
orbit.
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Low Earth Orbit (LEO)
LEO satellites are much closer to the earththan GEO satellites, ranging from 500 to1,500 km above the surface.
LEO satellites dont stay in fixed positionrelative to the surface, and are only visiblefor 15 to 20 minutes each pass.
A network of LEO satellites is necessaryfor LEO satellites to be useful
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LEO (cont.)
Disadvantages A network of LEO satellites is needed, which
can be costly
LEO satellites have to compensate forDoppler shifts cause by their relativemovement.
Atmospheric drag effects LEO satellites,causing gradual orbital deterioration.
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Doppler Shift
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Cospas-Sarsat system
the emergency radio beacons was at a frequencyof 121.5 MHz.
98% of the alerts were false
Due to the interference to this band The 121.5-MHz system relies entirely on the Doppler
shift, the carrier does not carry any identification information.
The power is low, typically a few tenths of a watt, which limits locational accuracy to about 10 to 20 km.
the 121.5-MHz service was terminate onFebruary 1, 2009
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S r h nd R u S t llit
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Search and Rescue SatelliteAided Tracking (SarSat)
Newer system operating at the band 406MHz are being introduced.
accuracy to 3 to 5 km
The 406-MHz carrier is modulated withinformation such as an identifying code,the last known position, and the nature of
the emergency.
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Medium Earth Orbit (MEO)
A MEO satellite is in orbit 8,000 km -18,000 km
MEO satellites are visible for much longerperiods of time than LEO satellites,usually between 2 to 8 hours.
MEO satellites have a larger coverage areathan LEO satellites.
A.k.a. Intermediate Circular Orbits (ICO),
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Highly Elliptical Orbit (HEO)
Known as Molniya Orbit Satellites Used by Russia for decades.
Molniya Orbit is an elliptical orbit. The
satellite remains in a nearly fixed positionrelative to earth for eight hours.
A series of three Molniya satellites can act likea GEO satellite.
Useful in near polar regions.
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Other Orbits (cont.)
High Altitude Platform (HAP) One of the newest ideas in satellite
communication.
A blimp or plane around 20 km above theearthssurface is used as a satellite.
HAPs would have very small coverage area,but would have a comparatively strong
signal. Cheaper to put in position, but would require
a lot of them in a network.
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INTELSAT
Stand for International TelecommunicationsSatellite.
created in 1964 and currently has over 140
member countries
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one 36 MHztransponder is capable
of carrying about9000 voice channels, ortwo analog TV channels,or about eight digitalTV channels.
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DOMSAT
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Direct broadcasting satellite system
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Characteristics of a few
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Characteristics of a fewcommunications satellites in use
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Satellite Application
Satellite Internet
Satellite Mobile
Satellite Radio
Satellite TV
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Satellite Internet
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Satellite Internet
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Satellite Internet
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Satellite Mobile
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Problems
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TRANSCEIVER DESIGN
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l bl k
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Typical receiver blocks
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Antenna
BBIFRF
(LNB) low-noise block converter
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Transponder
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D l i
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Duplexing
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RF i i h l
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RF communication channel
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P i Eff
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Propagation Effects
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RF T i Gl
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RF Transceiver at Glance
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Digital Communication System
RECEIVER
RFChannel
Output
Data
SourceDecoding
Channel
Decoder
Demodulator
SourceData
SourceCoding
ChannelCoding
Modulator
TRANSMITTER
Di it l T & R
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Digital Tx & Rx
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FM transceiver vs. Mobile
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Transceiver
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Disciplines required in RF system
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Disciplines required in RF systemdesign
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RF Ci it D i H
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RF Circuit Design Hexagon
Several trade-offs in
RF design In digital design only
one main trade-offbetween speed and
power
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Ulti t bj ti
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Ultimate objective
Single-chip transceiver Minimum external components
Inductors and capacitors integrated onchip
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A t
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Antenna
Convert RF signal toelectromagnetic waves and viceversa Same antenna is used for Tx and Rx
by using reciprocal feature
Antenna characteristics:
Operating frequency range
Size
Pattern coverage
Radiation pattern of antenna is aplot of the txed or Rxed signalstrength versus position aroundthe antenna
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Dipl ing Filt r
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Diplexing Filter
isolation Tx and Rx channels, to avoid interference Isolation between Tx and Rx should be about 120dB
Bandpass filterer at the input of the Rx can be used to attenuatethe transmitter signals.
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Same antenna should be used for Txand Rx
Duplexing filter should be used to
separate Tx from Rx signals, and
Provide attenuation between Tx and Rx
signals
Transmit/Receive (T/R) switch can be used in
half-duplex wireless systems
Antennae 2
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Antennae2
Antenna size decreases with the increasein frequency
=c/f
The gain of the antenna is proportional toits cross-sectional area divided by 2
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Filters
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Filters
To reject unwanted signals Important parameters:
Cut-off frequency
Insertion loss
Out-of-band attenuation rate Another important factor is integrability with other
circuit components Difficult to integrate high performance bandpass filters in IC
forms Has high insertion loss and low out-of-band attenuation rate
So, it uses off-chip filters located on the circuit board rather thanfully integrated filter
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All outside even they may being produced from different materials
Filter 2
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Filter2
From 800MHz to 4GHz Most of the BPF made with dielectric resonators which has small
size and high Q and reasonable IL
At IF (below 100MHZ)
BPF made by using Quartz or surface acoustic wave (SAW) devices
SAW filters have very sharp cutoff, but has high IL (20dB)
At higher MW and mmW
BPF uses waveguide resonators
LPFs have less stringent requirements than BPF: usually
are made of simple LC networks
Parallel coupled lines, or
Transmission line stubs
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Amplifier
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Amplifier
There are three main categories of amplifier usedin wireless:
Low noise amplifier (LNA)
Power amplifier (PA)
IF amplifier
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Amplifier 2
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Amplifier2
Importance specifications for Amplifiers: Power Gain (in dB)
Noise Figure (NF)
Intercept point (IP)
Transistor amplifier is non-linear devices
Saturation Saturation happen because the output voltage of an amplifier
cantexceed the bias voltage level.
Saturation is usually only an issue with PAs
Harmonic distortion usually is very low, however at cube of the input signal is
increases.
In practice it is important to keep distortion levels as low as 50-80dB below the output level.
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Amplifier 3
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Amplifier..3
Si transistors is inexpensive and havefrequencies up to several GHz
Previously Gallium Arsenide (GaAs) transistors
were required for frequencies at above 1GHz, However, GaAs processing is very expensive and
incompatible with silicon-based IC fabrication.
Another promising technology is silicon
germanium (SiGe), Which can be used at higher frequencies than silicon
and lower cost than GaAs,
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Mixer
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Mixer
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Oscillator
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Oscillator
Is required in the Rx and Tx to provide frequencyconversion
Typical Tx and Rx each may use as many as 4-6oscillators
RF oscillators Hartley, Colpitts oscillators
Use transistor with LC network (to control the frequency ofoscillation)
Better frequency control is uses quartz crystal in place of LCresonators (Pierce Oscillator)
In crystal oscillators is difficult to tune the frequency
PLL (frequency synthesizer) can be used for accurateoutput frequency
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Oscillator 2
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Oscillator2
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Hartley Oscillator Colpitts Oscillator
Pierce Oscillator Clapp oscillator
Transceiver Architecture for
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ground station
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Thank you