satellite communications

04/18/2304/18/23 EXCEL REVIEW CENTEREXCEL REVIEW CENTER 11


What are satellites?What are satellites?• Satellites are Satellites are

physical objects physical objects that orbit around that orbit around some celestial some celestial body.body.

• Can be by natureCan be by nature ((natural natural satellitesatellite) ) or man-or man-mademade ( (artificialartificial).).


What are some areas where What are some areas where satellites are applicable?satellites are applicable?

• CommunicationsCommunications

• MilitaryMilitary

• Space explorationSpace exploration

• Weather Weather forecastingforecasting

• Scientific researchScientific research

• MeteorologyMeteorology

• NavigationNavigation

• Search & RescueSearch & Rescue


Historical SatellitesHistorical Satellites• Echo Echo satellite satellite

(USA)(USA)

• Early 1960Early 1960

• A passive satelliteA passive satellite

• A 100-ft mylar-A 100-ft mylar-coated balloon coated balloon

• Accomplished the Accomplished the first transatlantic first transatlantic transmissiontransmission


Historical SatellitesHistorical Satellites

• Telstar I & IITelstar I & II (USA) (USA)

• July 10, 1962 & 1963July 10, 1962 & 1963

• An active satelliteAn active satellite

• (I) First to receive & (I) First to receive & transmit transmit simultaneously simultaneously (telephone calls)(telephone calls)

• (II) First to transmit (II) First to transmit live television images live television images between US and Europebetween US and Europe


Other Historical Other Historical SatellitesSatellites• Syncom ISyncom I (1963) (1963)

• Syncom IISyncom II (1963) (1963)

• Syncom IIISyncom III (1964)(1964)

• Intelsat 1Intelsat 1 (Early (Early Bird-1965)Bird-1965)

• MolniyaMolniya (USSR- (USSR-1966)1966)


System Architecture:System Architecture:• A. Space Segment a. Payload – receiving and transmitting antennas b. Platform - subsystems that permit payload to operate Structure, power supply, altitude orbit control, propulsion equipment and TTC (tracking, telemetry and command ) equipment

B. Ground Segment all the earth stations mostly connected to end user’s equipment


Classification of SatellitesClassification of Satellites

• According to the type of transmissionAccording to the type of transmission

• According to its angular velocityAccording to its angular velocity

• According to altitudeAccording to altitude

• According Path taken / OrbitAccording Path taken / Orbit

• According to territorial coverageAccording to territorial coverage

• According to the type of services According to the type of services offeredoffered


According to transmission According to transmission typetype

• Bus – transmit control signal to and Bus – transmit control signal to and from satellitefrom satellite

• Payload – Transmit user information Payload – Transmit user information signal onlysignal only


According to angular According to angular velocityvelocity

• Prograde – satellite angular velocity Prograde – satellite angular velocity is greater than that of the earthis greater than that of the earth

• Retrograde – Satellite angular Retrograde – Satellite angular velocity less than that of the earthvelocity less than that of the earth

• Synchronous – Satellite angular Synchronous – Satellite angular velocity equal to that of the earth velocity equal to that of the earth


• Usually non synchronous satellite can Usually non synchronous satellite can take an elliptical or circular orbit take an elliptical or circular orbit pattern.pattern.

• If the satellite takes an elliptical orbit If the satellite takes an elliptical orbit pattern, the nearest point it makes pattern, the nearest point it makes with the earth is called “ with the earth is called “ perigeeperigee” ” and the farthest distance it makes and the farthest distance it makes with the earth is called an “with the earth is called an “apogeeapogee”.”.


According to altitude According to altitude ( height )( height )

• Low Earth Orbiting ( LEO ) Low Earth Orbiting ( LEO )

• Medium Earth Orbiting ( MEO )Medium Earth Orbiting ( MEO )

• High Altitude or Geostationary Earth High Altitude or Geostationary Earth Orbiting ( GEO ) Orbiting ( GEO )


Satellite orbital location Satellite orbital location

- - LEO systemLEO system

- 100-300 mi- 100-300 mi

- 17,500 mph- 17,500 mph

- 1.5 hours- 1.5 hours

- 15 min/orbit- 15 min/orbit

- 1.0 to 2.5 GHz- 1.0 to 2.5 GHz

Ex. Ex. Iridium Satellite Iridium Satellite SystemSystem

- - MEO systemMEO system

- 6,000 – 12,000 - 6,000 – 12,000 mimi

- 9,580 mph- 9,580 mph

- 5 to 12 hours- 5 to 12 hours

- 2 to 4 - 2 to 4 hours/orbithours/orbit

- 1.2 to 1.66 GHz- 1.2 to 1.66 GHz

Ex.Ex. GPS of US GPS of US Defense Defense DepartmentDepartment


Satellite orbital locationSatellite orbital location

- - GEO systemGEO system

- 22,300 mi- 22,300 mi

- 6,879 mph- 6,879 mph

- 24 hours- 24 hours

- 24 hours/orbit- 24 hours/orbit

- 2 to 18 GHz- 2 to 18 GHz

Ex.Ex. INTELSAT INTELSAT systemsystem

Agila II satelliteAgila II satellite

• Arthur C. Clarke Arthur C. Clarke

• Clarke orbit or Clarke orbit or Clarke beltClarke belt

• Synchronous orbitSynchronous orbit


The Geosynchronous The Geosynchronous SatelliteSatellite• AdvantagesAdvantages

- Simpler ground - Simpler ground station trackingstation tracking

- No handover - No handover problemproblem

- Nearly constant - Nearly constant rangerange

- Very small Doppler - Very small Doppler shift in shift in

frequencyfrequency

• DisadvantagesDisadvantages

- Transmission - Transmission delaydelay

- Greater range loss- Greater range loss


According to path or orbital According to path or orbital patternpattern

• Polar orbit – Satellite path revolves Polar orbit – Satellite path revolves around the north and south pole.around the north and south pole.

• Equatorial – Satellite rotates in an Equatorial – Satellite rotates in an orbit above the equator.orbit above the equator.

• Inclined – Satellite has a slanting Inclined – Satellite has a slanting Orbital PatternOrbital Pattern

According to According to stabilization method stabilization method employed:employed:• Spinner SatelliteSpinner Satellite

• Three-Axis Stabilizer SatelliteThree-Axis Stabilizer Satellite



According to territorial According to territorial coveragecoverage• Domestic Satellite ( DOMSAT )Domestic Satellite ( DOMSAT )

services w/in a single countryservices w/in a single country

•Regional SatelliteRegional Satellite

services confined to specific regionsservices confined to specific regions

Ex. Palapa I,II Aguila IIEx. Palapa I,II Aguila II

•Global SatelliteGlobal Satellite

provides services globallyprovides services globally

Ex. INTELSAT (Intl. Satellite Org.)Ex. INTELSAT (Intl. Satellite Org.)

INMARSAT (Intl. Maritime Sat. INMARSAT (Intl. Maritime Sat. Org.)Org.)


Accdg. to the type of services Accdg. to the type of services offered:offered:• Fixed Satellite Service (FSS) – covers Fixed Satellite Service (FSS) – covers

links between satellites and fixed earth links between satellites and fixed earth stationsstations

• Mobile Satellite Service – covers sat. Mobile Satellite Service – covers sat. links to stations that maybe in motion links to stations that maybe in motion (mobile), incl. ships (Maritime Mobile, (mobile), incl. ships (Maritime Mobile, MMSS), (Aeronautical Mobile, AMSS) and MMSS), (Aeronautical Mobile, AMSS) and land vehicles (Land Mobile, LMSS)land vehicles (Land Mobile, LMSS)

• Broadcast Service – incl. TV (DBS-TV) Broadcast Service – incl. TV (DBS-TV) and audio (DBSA)and audio (DBSA)

• Inter Satellite Service – satellite to Inter Satellite Service – satellite to satellite cross-linkssatellite cross-links


Size, Mass and Cost of Size, Mass and Cost of satellitessatellites

SizeSize MassMass CostCost

Large Large satellitesatellite

> 1,000 kg> 1,000 kg > > $$ 100 m 100 m

Small Small satellitesatellite

500 – 1,000 500 – 1,000 kgkg

$$ 50 – 100 m 50 – 100 m

Mini-satelliteMini-satellite 100 – 500 kg100 – 500 kg $$ 5 – 20 m 5 – 20 m

Micro-Micro-satellitesatellite

10 – 100 kg10 – 100 kg $$ 2 – 3 m 2 – 3 m

Nano-Nano-satellitesatellite

< 10 kg< 10 kg < < $$ 1 m 1 m


Closer look at Closer look at Communication Satellite Communication Satellite Operation.Operation.


How we orient our antenna How we orient our antenna to a particular satellite? to a particular satellite?


Antenna OrientationAntenna Orientation

• Find our “ Find our “ look angleslook angles””

• Our look angles is composed of the ff:Our look angles is composed of the ff:

• The angle of elevation – formed The angle of elevation – formed between the plane of the wave radiated between the plane of the wave radiated from the earth station and the horizon.from the earth station and the horizon.

• Azimuth – Horizontal pointing angle of Azimuth – Horizontal pointing angle of the antenna.the antenna.


Spatial SeparationSpatial Separation

• Angular separation between satellite Angular separation between satellite in space operating at or near the in space operating at or near the same frequency.same frequency.


Picture picture…….Picture picture…….


Variables that influenced spatial Variables that influenced spatial separationseparation

• Bandwidth and side lobe of radiationBandwidth and side lobe of radiation

• RF carrier frequencyRF carrier frequency

• Encoding or modulation usedEncoding or modulation used

• Acceptable limits of interferenceAcceptable limits of interference

• Transmit carrier powerTransmit carrier power


Radiation PatternRadiation Pattern

• The radiation Pattern ( Footprint ) – is The radiation Pattern ( Footprint ) – is the geographical representation of the geographical representation of the satellite antenna radiation the satellite antenna radiation pattern.pattern.


3 categories of Satellite 3 categories of Satellite FootprintFootprint

• Earth – Radiation pattern having a Earth – Radiation pattern having a beamwidth of approximately 17beamwidth of approximately 17oo and and include coverage of approximately one include coverage of approximately one third of the earth’s surface.third of the earth’s surface.

• Zonal – coverage includes an area less Zonal – coverage includes an area less than one third of earth surfacethan one third of earth surface

• Spot – spot beams concentrate the Spot – spot beams concentrate the radiated power in a very small geographic radiated power in a very small geographic area area


Satellite orbital dynamicsSatellite orbital dynamics

•Orbital dynamicsOrbital dynamics – refers to the – refers to the forces that keep the satellite in forces that keep the satellite in orbit and the physical and orbit and the physical and mathematical laws that it follows.mathematical laws that it follows.


Fc

Fg

v Satellite orbit

Earth’s equator

Geocenter ofearth

c gF F

11

km km

4 x 10v ,m / s

R +h

2 23

2

gT Rh R ,km

4


Sample Problem 1Sample Problem 1

Determine the height of a certain Determine the height of a certain satellite in orbit with a sidereal satellite in orbit with a sidereal period of 30 hours.period of 30 hours.

A. 42, 628 miA. 42, 628 mi

B. 42, 628 km B. 42, 628 km

C. 43, 275 miC. 43, 275 mi

D. 43, 275 kmD. 43, 275 km

2 23

2

gT Rh R ,km

4


Satellite RangeSatellite Range

d

2 2 2d R h R cos R sin



What is the maximum acceptable What is the maximum acceptable satellite range for a geosynchronous satellite range for a geosynchronous satellite?satellite?

A. 41,191 kmA. 41,191 km

B. 40,200 kmB. 40,200 km

C. 41,191 miC. 41,191 mi

D. 40,200 mi D. 40,200 mi



Frequency AllocationFrequency Allocation

• Common frequenciesCommon frequencies– 6/4 GHz6/4 GHz– 14/12 GHz14/12 GHz

• UplinkUplink ( (first numberfirst number))

• DownlinkDownlink ( (22ndnd number number))


Microwave frequency Microwave frequency bandsbands

Band designation Frequency range (GHz)

L 1-2

S 2-4

C 4-8X 8-12

Ku 12-18K 18-27

Ka 27-40

Millimeter 40-300

Submillimeter >300


Frequency bands used Frequency bands used in satellite in satellite communicationscommunications

Frequency Band

225 - 390 MHz P

350 - 530 MHz J

1530 - 2700 MHz L

2500 - 2700 MHz S

3400 - 6425 MHz C7250 - 8400 MHz X

10.95 - 14.5 GHz Ku17.7 - 21.2 GHz Kc

27.5 - 31 GHz K

36 - 46 GHz Q

46 - 56 GHz V

56 - 100 GHz W


Actual satellite Actual satellite frequenciesfrequencies

•Commercial C-band6/4 GHz 5.925 – 6.425 GHz Uplink

3.7 – 4.2 GHz Downlink

•Military C-band8/7 GHz 7.9 – 8.4 GHz Uplink

7.25 – 7.75 GHz Downlink


The Block diagram The Block diagram sections….sections….


Satellite System Link ModelsSatellite System Link Models

• An uplink sectionAn uplink section

• A satellite transponderA satellite transponder

• A downlink sectionA downlink section


The Uplink ModelThe Uplink Model

Modulator(FM, PSK, or

QAM)BPF Mixer BPF HPA

MWGenerator

6 or 14 GHz

Basebandin (FDM orPCM/TDM)

Up-converter

To satellitetransponder


The satellite transponderThe satellite transponder

BPFLow-noiseamplifier

(LNA)Mixer BPF

Low-poweramplifier

TWT

MW shiftoscillator

2 GHz

Frequency translator

To earthstation4 or 12

GHz

From earthstation6 or 14

GHz


The Downlink ModelThe Downlink Model

Baseband out(FDM or PCM/

TDM)

BPF LNA Mixer BPFDemodulator(FM, PSK, or

QAM)

MWGenerator

4 or 12 GHz

Down-converter

From satellitetransponder


Systems Parameters….Systems Parameters….

Amo na ni ang libog sa Amo na ni ang libog sa problema……problema……


System parametersSystem parameters

• Effective Isotropic Radiated Power (EIRP)Effective Isotropic Radiated Power (EIRP)

r tEIRP P G

r(dBW ) t(dBW ) (dB)P P Losses

dBW r dBW t dBEIRP P G


System parametersSystem parameters• Transmit power and bit energyTransmit power and bit energy

tb t b

b

PE P T

f

Where Eb = energy per bit

Pt = transmitter output power

Tb = Period ( time ) of one bit

fb = frequency of the bit



• Equivalent Noise TemperatureEquivalent Noise Temperature

e oT T NF 1 Where Te = equivalent noise temperature ( kelvin )

To = Temperature of environment ( kelvin )

NF = Noise figure


System parametersSystem parameters• Noise DensityNoise Density

o eN

N kTBW

Where No = noise density

N = noise power

BW = Bandwidth

k = Boltzmann’s constant ( 1.38 x 10 -23 j/k )

Te = equivalent noise temperature



• Carrier-to-Noise Density RatioCarrier-to-Noise Density Ratio

o e

C C

N kT

Carrier to noise density ratio – is the average wideband carrier noise density ratio. The wide band carrier power is the combined power of the carrier and its associated side bands.



• Energy-of-Bit-to-Noise Density Ratio Energy-of-Bit-to-Noise Density Ratio

b b

o b

CE f CBW

NN NfBW


System parametersSystem parameters• Gain-to-Equivalent Noise Gain-to-Equivalent Noise

Temperature RatioTemperature Ratio

r

e e

G G LNAG

T T

This is a figure of merit used to represent the quality of a satellite or earth station receiver.

Where

Gr = gain of the receiver antenna

G( LNA ) = gain of the satellite / earth station low noise amplifier

Te = equivalent noise temperature ( Kelvin )


System link System link equations……..equations……..

Applying what we have Applying what we have learned into the system…..learned into the system…..


Over all signal linkages Over all signal linkages profileprofile


System link equationsSystem link equations

• Uplink EquationsUplink Equations


System link equationsSystem link equations

• Downlink equationsDownlink equations


Let us see how much did Let us see how much did we remember about the we remember about the lesson…..lesson…..


Problem solving ….Problem solving ….


Sample Problem 3Sample Problem 3What is the free space loss What is the free space loss between an earth station and a between an earth station and a GEO satellite when the elevation GEO satellite when the elevation angle is 30angle is 30 and the uplink and the uplink frequency is 5 GHz.frequency is 5 GHz.

A. 198.13 dB A. 198.13 dB

B. 198.13 dBmB. 198.13 dBm

C. 200.08 dBC. 200.08 dB

D. 200.08 dBmD. 200.08 dBm

92 4 20 20P GHz kmL . log f logd



April 2004 Board ExamApril 2004 Board ExamCalculate the free space loss Calculate the free space loss between a satellite transmitter between a satellite transmitter and a satellite receiver at a and a satellite receiver at a distance of 25,000 km using 6 distance of 25,000 km using 6 GHz.GHz.

A. 103.6 dBA. 103.6 dB

B. 102 dBB. 102 dB

C. 196 dBC. 196 dB

D. 96.4 dBD. 96.4 dB

92 4 20 20P GHz kmL . log f logd


April 2004 Board ExamApril 2004 Board ExamAn uplink transmitter of a satellite system An uplink transmitter of a satellite system operates at 6 GHz with a transmitter power operates at 6 GHz with a transmitter power of 12 kW and an antenna gain of 50 dBi. The of 12 kW and an antenna gain of 50 dBi. The receiver on a geostationary satellite has an receiver on a geostationary satellite has an antenna gain of 40 dBi. The elevation angle antenna gain of 40 dBi. The elevation angle to the satellite from the ground is 45 to the satellite from the ground is 45 degrees, calculate the receive signal degrees, calculate the receive signal strength at the satellite. (height of satellite strength at the satellite. (height of satellite above equator is 36,000 km, earth radius = above equator is 36,000 km, earth radius = 6400 km).6400 km).A. 38.7 dBmA. 38.7 dBmB. 70.8 dBmB. 70.8 dBmC. -70.8 dBmC. -70.8 dBmD. -38.7 dBmD. -38.7 dBm

dBm T dBmRSL P Total gain Total loss

310

1 10T(W )

T(dBm)

PP log

x W


Sample Problem 4Sample Problem 4Determine the transmission delay Determine the transmission delay when a signal is transmitted by an when a signal is transmitted by an earth station to a geosynchronous earth station to a geosynchronous satellite and then received by the satellite and then received by the same earth station.same earth station.

A. 239 A. 239 ss

B. 239 sB. 239 s

C. 239 ms C. 239 ms

D. 239 nsD. 239 ns

total distanceX 'mission delay

velocity


Sample Problem 5Sample Problem 5Satellite communication link between Satellite communication link between Tanay Earth Station, Philippines and Tanay Earth Station, Philippines and Mt. Fucino Earth Station, Italy, is to be Mt. Fucino Earth Station, Italy, is to be established. The uplink frequency of established. The uplink frequency of Tanay Earth Station is 6175 MHz, what Tanay Earth Station is 6175 MHz, what is the downlink frequency of Mt. is the downlink frequency of Mt. Fucino Earth Station if the osc shift is Fucino Earth Station if the osc shift is 2.225Ghz?2.225Ghz?

A. 3950 GHzA. 3950 GHz

B. 3950 PHzB. 3950 PHz

C. 3950 MHz C. 3950 MHz

D. 3.950 MHz D. 3.950 MHz

d u of f f



What is the uplink frequency What is the uplink frequency when the downlink frequency when the downlink frequency is 4.1 GHz?is 4.1 GHz?

A. 6.325 MHzA. 6.325 MHz

B. 6.325 GHzB. 6.325 GHz

C. 6.325 THzC. 6.325 THz

D. 6.325 PHzD. 6.325 PHz

u d of f f


Sample Problem 7Sample Problem 7An earth station satellite transmitter An earth station satellite transmitter has an HPA with a rated saturated has an HPA with a rated saturated output power of 10,000 W. The back-output power of 10,000 W. The back-off ratio is 6 dB, the branching loss is off ratio is 6 dB, the branching loss is 2 dB, the feeder loss is 4 dB and the 2 dB, the feeder loss is 4 dB and the antenna gain is 40 dB. Determine the antenna gain is 40 dB. Determine the EIRP.EIRP.

A. 68 dBW A. 68 dBW

B. 68 dBB. 68 dB

C. 68 dBm C. 68 dBm

D. 68 dBrnD. 68 dBrn

r(dBW ) t(dB)dBWEIRP P G

r(dBW ) t(dBW ) (dB)P P Total losses


Sample Problem 8Sample Problem 8Determine the carrier-to-noise Determine the carrier-to-noise density ratio for a receiver with density ratio for a receiver with a –70 dBW input carrier power, a –70 dBW input carrier power, an equivalent noise temperature an equivalent noise temperature of 180 K, and a bandwidth of 20 of 180 K, and a bandwidth of 20 MHz.MHz.

A. 136.05 dBmA. 136.05 dBm

B. 137.03 dBB. 137.03 dB

C. 136.05 dB C. 136.05 dB

D. 137.03 dBmD. 137.03 dBm


Sample Problem 9Sample Problem 9Determine the total noise power Determine the total noise power for a receiver with an input for a receiver with an input bandwidth of 20 MHz and an bandwidth of 20 MHz and an equivalent noise temperature of equivalent noise temperature of 600 K.600 K.

A. 16.56 pWA. 16.56 pW

B. 16.56 B. 16.56 WW

C. 16.56 nWC. 16.56 nW

D. 165.6 fWD. 165.6 fW


Sample Problem 10Sample Problem 10Determine the energy of bit-to-Determine the energy of bit-to-noise density ratio when the noise density ratio when the receiver input carrier power is –receiver input carrier power is –100 dBW, the receiver input 100 dBW, the receiver input noise temperature is 290 K, and noise temperature is 290 K, and a 60-Mbps transmission rate is a 60-Mbps transmission rate is used.used.A. 26.2 dBmA. 26.2 dBmB. 26.2 dB B. 26.2 dB C. 25.3 dBm C. 25.3 dBm

D. 25.3 dB D. 25.3 dB


End of the reviewEnd of the review

satellite communications

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