Satellite TechnologySatellite Technology

■ Assoc. Prof Dr Syed Idris Syed HassanAssoc. Prof Dr Syed Idris Syed Hassan■ School of Electrical and Electronic EngSchool of Electrical and Electronic Eng■ Universiti Sains MalaysiaUniversiti Sains Malaysia■ Seri Iskandar , 31750 PerakSeri Iskandar , 31750 Perak

ConceptConcept

Transponder

Earth station (site A) Earth station(site B)

IRRADIUM

downlinkdownlink

uplinkuplink

downlinkdownlink

uplinkuplink

ApplicationsApplications

■ Communication Communication (truncking call)(truncking call)

■ TeleconferenceTeleconference■ TelemedicineTelemedicine■ TV BroadcastingTV Broadcasting■ Data communicationData communication■ Telemetry(TEC, Telemetry(TEC,

remote sensing etc)remote sensing etc)

■ Weather telecastWeather telecast■ NavigationNavigation■ GPSGPS■ Security/Calamity Security/Calamity

monitoringmonitoring■ Standard TimeStandard Time■ militarymilitary

Type of SatellitesType of Satellites

■ LEO -Low Earth orbital 100-16,000Km LEO -Low Earth orbital 100-16,000Km (90min to 12hrs orbiting the earth)(90min to 12hrs orbiting the earth)

■ MEO - Medium Earth Orbital MEO - Medium Earth Orbital 16,000-36,000 Km (12 - 24 hrs orbiting 16,000-36,000 Km (12 - 24 hrs orbiting the earth)the earth)

■ GEO - Geosynchronous Earth Orbital - GEO - Geosynchronous Earth Orbital - 36,000 Km ( The satellite appears to be 36,000 Km ( The satellite appears to be stationary over one point on earth)stationary over one point on earth)

Look angle (Elevation)Look angle (Elevation)

)sin()sin()cos()cos()cos(cos

cos21.

tan

sin)(

2/12

seesse

s

e

s

es

LLllLL

r

r

r

rrdei

satelliteandstationearthbetweencedisdwhered

ElCos

+−=

−

+=

=

=

γ

γ

γ

ElEl

continuecontinue

■ Le = Earth station LatitudeLe = Earth station Latitude■ le = Earth station longitudele = Earth station longitude■ Ls = Satellite latitude ( = 0 for GEO)Ls = Satellite latitude ( = 0 for GEO)■ ls = Satellite longitudels = Satellite longitude■ rs = Satellite orbital radius ( ~ 36,000 km for GEO)rs = Satellite orbital radius ( ~ 36,000 km for GEO)■ re = earth radius = 6370 kmre = earth radius = 6370 km

For GEO satelliteFor GEO satellite

Cos Cos L Cos l le s eγ = −( ) ( )

Looking angle(azimuth)Looking angle(azimuth)

■ Consider for GEO onlyConsider for GEO only

( ) ( )( ) ( )α

γ

γ

=− −

− −

= − + +

−2

0 5

1tansin sin

sin sin

. ( )

s s L

s s l l

wheres l l L

e

e s

s e e

NN

SS

ESES

SatSat

EEWW

αα

continuecontinue

■ If Earth station is in the North Latitude ,If Earth station is in the North Latitude ,

the azimuth will be as follow (refer to N)the azimuth will be as follow (refer to N)

Satellite on the Eastof Earth station

Az=180-α

Satellite on the Westof Earth station

Az=180+α

continuecontinue

■ If the Earth station is in the South If the Earth station is in the South latitude , the azimuth will be (refer to N)latitude , the azimuth will be (refer to N)

Satellite on the Eastof Earth station

Az=α

Satellite on the Westof Earth station

Az=360-α

ExampleExample

Parameter MEASAT JCSAT Superb C

Longitude 91.5 E 128 E 144 E

EIRP (ku)54MHz 56.5 dBW 42 dBW 50.8 dBW

Beacon signal 6 Ghz ? 12.747ghzIf 1447.5MHz

12.255ghzif 955.0 Mhz

Vedio IF 980-1170 Mhz 950-1400mhz 1090-1433mhz

Looking anglefrom 100E 5N

El=78.05Az=216.5

El=55.9Az=108.4

El=37.7Az=100.3

Link budgetLink budget

Noise Power Budget for 54 MHz channelNoise Power Budget for 54 MHz channel

Boltzmann’s ConstantBoltzmann’s Constant = - 228.6 dBW/K/Hz= - 228.6 dBW/K/Hz

Receiving system noise temp.Receiving system noise temp. = 28.5 dBK= 28.5 dBK

Ku- Band ‘s channel bandwidthKu- Band ‘s channel bandwidth == 77.3 77.3 dBdB

Receiving noise level Receiving noise level - 122.8 - 122.8 dBdB

For C/N about 10 dB to allow rain and other fading For C/N about 10 dB to allow rain and other fading the signal level should be -112.8 dBthe signal level should be -112.8 dB

continuecontinue

( )C N

P G

kTB RG

EIRP

N LG

where

EIRP Equivalent isotropic radiated power P G

N ceived noise level kTB

L Path lossR

G ceiving antenna gain

R dis ce between earth station and satellite

wavelength of operating frequency

t tr

r pathr

t t

r

path

r

/

Re

Re

tan

=

=

= == =

= =

===

λπ

πλ

λ

4

4

2

2

continuecontinue

In decibelIn decibel

[ ] [ ] [ ] [ ]

[ ] [ ] [ ] [ ]

P dB C N dB N EIRP dB G dB L dB

therefore to calculate antenna size we obtain G

G dB P dB L dB EIRP dB

and parabolic size

AG

antenna efficiency

r r r path

r

r r path

r

= + = + −

= + −

=

=

/

λπη

η

2

4

ContinueContinue

■ Parabolic antenna diameterParabolic antenna diameter

π λπη

λ

π ηη

D G

DG

antenna efficiency

r

r

2 2

2

2

4 4

06

=

=

= = .

ContinueContinue

■ MEASATMEASAT

[ ] [ ] [ ]G dB C N dB N EIRP dB L dB

dB dB dB dB

dB

This gain can be achieved u g m diameter dish

r r path= + − +

= − − +=

/

. .

.

sin . ( ) .

10 122 8 56 5 205

35 7

0 75

continuecontinue

■ JCSATJCSAT

[ ] [ ] [ ]G dB C N dB N EIRP dB L dB

dB dB dB dB

dB

This gain can be achieved u g m diameter dish

r r path= + − +

= − − +=

/

.

.

sin . ( ) .

10 122 8 42 205

50 2

3 6

continuecontinue

■ Superbird CSuperbird C

[ ] [ ] [ ]G dB C N dB N EIRP dB L dB

dB dB dB dB

dB

This gain can be achieved u g m diameter dish

r r path= + − +

= − − +=

/

. .

.

sin . ( ) .

10 122 8 50 8 205

414

1 32

Teleconference SystemTeleconference System

LNA/HPALNA/HPATransceiverTransceiverQPSK modQPSK mod& demod& demod

CODECCODEC

1.536Mbps1.536Mbps

TVTVmonitormonitor

IDUIDU ODUODU

Data communicationData communication

LNA/HPALNA/HPATransceiverTransceiverQPSK modQPSK mod& demod& demod

1.536Mbps1.536MbpsPCPC

RouterRouter

&&TranscieverTransciever

IDUIDU ODUODU

Other factors need to considerOther factors need to consider

■ Antenna Antenna ■ Rain attenuationRain attenuation■ Beam FootprintBeam Footprint■ Mismatch lossesMismatch losses■ MisalignmentMisalignment■ Scintillation ~for low elevationScintillation ~for low elevation■ troposphere/atmospheretroposphere/atmosphere■ Bit error rateBit error rate

To avoid blockinguse offset antenna

no blocking

(6) Depointing error

Antenna gain will be reduced according to deviation from the true angle. Thisis given by

G dB G dBoe

db

( ) ( )= −

12

3

2θθ

where θe is the depointing error.therefore attenuation due to depointing error is

A dB e

dB

( )=

12

3

2θθ

Parabolic antenna feed

Horn a a

Le α b α bE R R

Le E

Ln Ln

E-plane Sectorial horn H-plane sectorial horn

a b

Le α1

α2

Ln

Primidal horn

L Re = 2λ L Rn = 3λ

Directivite gain

(I) E-plane sectorial

( ) ( )D

L L C x S x

xee n=

+322

2 2

πλ

C x t dtx

( ) cos( / )=∫ π20

2

S x t dtx

( ) sin( / )=∫ π20

2 and x= Le / 2λR

(ii) H-plane Sectorial

[ ] [ ]{ }DL R

LC x C x S x S xn

e

n

= − + −4

1 22

1 22π

λ ( ) ( ) ( ) ( )

xR

L

L

Rn

n1

1

2= +

/

/

/

/

λλ

λλ

xR

L

L

Rn

n2

1

2= −

/

/

/

/

λλ

λλ

(iii) Primidal horn

DL L

D Dpe n

e n=πλ2

32

* all the above horn antennas follow the following condition

( )D a D b

2 2 181 2 1 2 0

2 2

2

2

πσ λ π σσ

λ−

−

− − −

=

D is the desired directivitya,b are the dimension of the feeding waveguide

σλ

=Ls

( )L slant length of the horn

R L

s

e

=

= +2 22/

For large horn (assuming 50% efficiency)

Le = 2σλ L

D

Lne

= λπ

2

2

R L b LLe

se

= −

−( ) /

21 4

σ = D / .15 4

Scalar

Using circular waveguide. This type of feed is used for receiving antenna.It consists of 3 - 7 concentric rings of a quarter-wavelength broad.

feed

λ/ 4

Log periodic

Ln L1

α feed

dn

d1

First element

L F1 10 48=. λ where

FL

DL

D=

+1 and λ1

83 10=× fmin

D is the diameter of the first dipole = 2 a1

LD a=λ1

14 a1 is the radius of the first elementOther elements follow

( )aLL

Dn

n=2

; d Ln n= 2σ ; α τ

σ= −

−21

41tan

and τ= =+ +d

d

L

Ln

n

n

n

1 1

Gain(dB) 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0σ 0.139 0.147 0.157 0.163 0.168 0.172 0.174 0.176 0.178τ 0.782 0.822 0.865 0.892 0.916 0.928 0.940 0.950 0.964

Helical antenna(Axial mode)

S

2r d

C = π d α

S

LDesign parameters2

33

2λ λ<<C

where C = π d2

33

2λ λ<<d

5 20o o<<α where α = helix angle

S = C Tan α and L = wire length per turn = C/cos αDirectivity

( )( )D n S C=152

λλ

Rain attenuationRain attenuation

1%1%

0.1%0.1%

0.01%0.01%

% of time exceedance% of time exceedance

2020 4040 6060 8080 100100mm/hrmm/hr

rain raterain rate

ContinueContinue

■ For TV and broadcasting usually the For TV and broadcasting usually the reliability is not very critical , so 99% is reliability is not very critical , so 99% is okay and this equivalent to 1% of okay and this equivalent to 1% of exceedance of timeexceedance of time

■ For data other digital com the reliability For data other digital com the reliability of 99.99% is probably chosen and this of 99.99% is probably chosen and this is equivalent to 0.01% of exceedance of is equivalent to 0.01% of exceedance of time.time.

continuecontinue

Att aR Lbpath= 0 01.

For 99.99% reliability, the attenuation is calculated asFor 99.99% reliability, the attenuation is calculated as

where a and b are constants relied on frequencywhere a and b are constants relied on frequency

RR0.01 0.01 rain rate at 0.01% of exceedance of timerain rate at 0.01% of exceedance of time

LLpath path is slant path where signal passed the rainis slant path where signal passed the rain

Slant pathSlant path

LLpathpath

RainRainheightheight~3km~3km

Footprints

Gs

Single beam θ3dB r=35,775 Km(3dB contour)

10o N footprint

d R=6378Km

10o S 20

d/2 = R sin 20 = 6378 X 0.3420 = 2181.4 Km

θ3dB = 2( ) = 2 ( ) = 2(arctan(0.060976))arctan arctan.

,

d

r2 21814

35 775

= 2 X 3.49o = 6.98o

( )G dBs =

× = =48360 0 65

6 98645 281

2.

..

For 12 Ghz ----> λ = 0.025 m

D mdB

= = × =70 70 0 025

6 980 251

3

λθ

.

..

Footprint can be stated in EIRP or power density flux (PDF) contours of3dB, 5dB etc.

eg

PDF (dBW/m2)=EIRP(dB) - Lp (dB)

where Lp is the propagation path loss (i.e ( )λπ42

r )

3dB contour

EIRP = Pt Gt = 56.5 dB therefore power transmitted=56.5 -28.1=26.4dBW

PFD = 56.5 - 205.1 = -148.6 dBW/m2

5dB contour

PDF= -148.6-2 = 150.6 dBW/m2

θ λ5

91 91 0 025

0 2519 06dB

o

D= = × =.

..

Elliptically shape beam

Usually using elliptically shape reflector

D2

D1

θ1

θ2

G dB31 2

48360= ηθθ

D11

70= λθ

D22

70= λθ

θ λ5

11

91dB D

= and θ λ5

22

91dB D

=

Array antennasAntenna array may consists of arrangement of dipoles , slots or patches insuch that a directive beam is formed.

θ d sinθ

1 d 2 3 N ( )( )E E e e eo

jkd j kd j N kd=+ + + +− − −−1 2 1sin sin sin. . . . . . .. . .θ θ θ

=

E N

No sin /

sin /

ϕϕ

2

2 where ϕ θ=kd sin

Radiation pattern (beam)main beam

θ λ3

102dB Nd=

in degrees

sidelobes

Changing the direction of the beam electronically

using phase shifter(parallel arangement)

θo

θο 2θο 3θο 4θο ....................Νθο

E EN

No

o

o=

−

−

sin

sin

ϕϕ

ϕϕ2

2 where ϕ θo okd=sin and d < 0.5 λ

θ λθ3

102dB

oNd≈

cos

(serial arrangement)

θο θο θο θο ....... .............θο

Using delay line

The serial phse shifter arrangement can be replaced by delay line in suchthat

ϕ θo okd kL= =sin where L is the electrical length of the delay line.

Implementation of multiple beam

1 2 3

amplifier amplifier amplifier

-ϕ1 ϕο +ϕ1 ϕο ϕο ϕο −ϕ1 ϕο +ϕ1

sum sum sum

beam 1 beam 2 beam 3eg. f = 12 Ghz then λ = 0.025 m , N = 20 d = 0.006mθο =0

θ λθ3

0102 102 0 025

20 0 006 021dB

oNd≈ = ×

×=

cos

.

. cos

θο=20

θ3102 0 025

20 0 006 2022 6dB

o≈ ××

=.

. cos.

θο=40

θ3102 0 025

20 0 006 4027 6dB

o≈ ××

=.

. cos.

Beam forming Network

Butler beam forming

1 2 3 4 5 6 7 8

-45o -45o -45o -45o

-67.5o -22.5o -22.5o -67.5o

1R 4L 3R 2L 2R 3L 4R 1L

Directional coupler/power divider

Right beam 1 2 0.707 / 90o

1V / 0o 0.707V / 0o

Left beam 4 3 0.707 V / 0o

1V / 0o 0.707V / 90o