Satellite Space LinkSatellite Space LinkLinkLink--power Budgetpower Budget

Satellite System ParametersSatellite System Parameters11. Effective Isotropic Radiated Power (EIRP). Effective Isotropic Radiated Power (EIRP)

A key parameter in link budget is the A key parameter in link budget is the equivalent/Effective isotropic radiated power:equivalent/Effective isotropic radiated power:

[EIRP]=[Ps]+[G] dBW[EIRP]=[Ps]+[G] dBW[Ps][Ps]-- the power at the antenna input (dBW)the power at the antenna input (dBW)[G] [G] –– Antenna Gain (dB)Antenna Gain (dB)

Satellite System ParametersSatellite System Parameters11. Effective Isotropic Radiated Power (EIRP). Effective Isotropic Radiated Power (EIRP)

For Parabolic Antennas with efficiency For Parabolic Antennas with efficiency ==00..5555--00..73 73 , the gain can be approximated by:, the gain can be approximated by:

G=G=((1010..472 472 ffD)D)22

Where Where ff –– the operating frequency in GHzthe operating frequency in GHzD D –– Ant. Diameter in mAnt. Diameter in m

EIRP ExampleEIRP ExampleA Sat. downlink at A Sat. downlink at 12 12 GHz operates with a transmit GHz operates with a transmit power (Pt) of power (Pt) of 66W and an antenna diameter of W and an antenna diameter of 3 3 m m and efficiency and efficiency 00..5555. Calculate EIRP. Calculate EIRP

Sol.Sol.G=G=((1010..472472fD)fD)22==00..5555x(x(1010..472472xx1212xx33))22==7878..168168[G]=[G]=10 10 Log(Log(7878..168168)=)=4848..9 9 dBdB

[EIRP]=[EIRP]=1010loglog66++4848..99= = 5656..7 7 dBWdBW

Satellite System ParametersSatellite System Parameters22. Free Space Path Loss (Lp). Free Space Path Loss (Lp)

Lp is the loss incurred by an electromagnetic Lp is the loss incurred by an electromagnetic wave as it propagates in a straight line through wave as it propagates in a straight line through vacuum with no absorption or reflection of vacuum with no absorption or reflection of energy from nearby objectsenergy from nearby objects

Lp is frequency dependent (wavelength Lp is frequency dependent (wavelength ) ) and increases with distance and increases with distance r r ::

22

P44L

crfr

Satellite System ParametersSatellite System Parameters

cfrLog

cfrLog 420410]L[

2

P

rLogfLogc

Log 2020420]L[ P

Lp in dB:Lp in dB:

With With c=c=33xx10108 8 m/sm/s, , f f in GHz and in GHz and rr in Km, Lp in Km, Lp in dB:in dB:

KmGHz rLogfLog 20204.92]L[ P

EIRP ExampleEIRP ExampleFind Lp for an uplink operating at Find Lp for an uplink operating at 6 6 GHz with a GHz with a distance r=distance r=4200042000Km. If the ES EIRP is Km. If the ES EIRP is 120 120 dBW, dBW, what will be the RX power in dBm.what will be the RX power in dBm.

Sol.Sol.[Lp]=[Lp]=9292..44+ + 20 20 Log (Log (4200042000) + ) + 20 20 Log(Log(66))[Lp]=[Lp]=200200..4 4 dBdB

[P[PRXRX]=]=120120--200200..44==--8080..4 4 dBW=dBW=--110110..4 4 dBmdBm

Satellite System ParametersSatellite System Parameters33. Additional Atmospheric and Ionospheric . Additional Atmospheric and Ionospheric

Losses (Lu/Ld)Losses (Lu/Ld)

Atmospheric gases result in losses by absorption. Atmospheric gases result in losses by absorption. These losses usually amount to a fraction of a These losses usually amount to a fraction of a dB[AA]. dB[AA].

Also, the ionosphere introduces a depolarization Also, the ionosphere introduces a depolarization loss [PL]loss [PL]

Satellite System ParametersSatellite System Parameters44. Feeder and Branching Losses (L. Feeder and Branching Losses (Lbfbf))Losses will occur in the connection between Losses will occur in the connection between waveguides, filters couplers and Branching units waveguides, filters couplers and Branching units

55. Antenna Misalignment Losses (AML) . Antenna Misalignment Losses (AML) Loss that occurs as a result of having the ES and Sat. Loss that occurs as a result of having the ES and Sat. antennas being offantennas being off--axis. For ES, this loss is called axis. For ES, this loss is called antenna pointing loss. antenna pointing loss.

Loss that occurs as a result of having polarization Loss that occurs as a result of having polarization misalignmentmisalignment

66. Polarization Misalignment Losses (PL) . Polarization Misalignment Losses (PL)

Antenna MisalignmentsAntenna Misalignments

Example: TelSat Canada DesignExample: TelSat Canada Design

Satellite System ParametersSatellite System Parameters77. Back. Back--off Loss (Loff Loss (Lbobo=[BO]=[BO]ii/[BO]/[BO]oo))

HPAs used in ES HPAs used in ES transmitters and transmitters and TWTs used in Sat. TWTs used in Sat. transponders are transponders are nonlinear devices: nonlinear devices: their gain (outputtheir gain (output--input) is input) is dependent on the dependent on the input signal. input signal.

Satellite System NoiseSatellite System NoiseThe RX power in a Sat. link is very small (couples of The RX power in a Sat. link is very small (couples of pW)pW) amplification can be used to bring the signal amplification can be used to bring the signal strength up to an acceptable level.strength up to an acceptable level.

The main source of noise is the random thermal The main source of noise is the random thermal motion of electrons + thermalmotion of electrons + thermal--like noise from like noise from antenna radiationantenna radiationThe total noise power can be :The total noise power can be :

NNBKTP NKK--Boltzmans const. = Boltzmans const. = 11..3838xx1010--2323J/KJ/KTTNN--temperature of the environment (K)temperature of the environment (K)BBNN-- Noise Bandwidth (Hz)Noise Bandwidth (Hz)

Satellite System NoiseSatellite System Noise

e2e110,2 KT)T(N antTKG

Another parameter is the noise factor F:Another parameter is the noise factor F:

TeTe-- Equivalent noise temperature (K)Equivalent noise temperature (K)

The Noise Figure NF is:The Noise Figure NF is:

Log(F)10[NF]

For a cascaded amplifier:For a cascaded amplifier:

TT1F e 1)T(FTe )Log(T10][T ee

Satellite System NoiseSatellite System Noise

e2e110,2 KT)T(N antTKG

In general, for a cascaded system N is:In general, for a cascaded system N is:

TeTe-- Equivalent noise temperature (K)Equivalent noise temperature (K)

The Noise Figure NF is:The Noise Figure NF is:

Log(F)10[NF]

For a cascaded amplifier:For a cascaded amplifier:

...GGT

GTTTT

21

e3

1

e2e1ants

Noise ExampleNoise ExampleAn Ant. Has a noise temperature of An Ant. Has a noise temperature of 35 35 K and is K and is matched into a receiver which has a noise matched into a receiver which has a noise temperature of temperature of 100100K. Calculate the noise density K. Calculate the noise density and the noise power with a BW=and the noise power with a BW=3636MHz.MHz.

Sol.Sol.No=KT= (No=KT= (3535++100100)x)x11..3838xx1010--2323==11..8686xx1010--2121 JJPPNN=KTB==KTB=11..8686xx1010--2121xx3636xx101066==00..067 067 pWpW

Noise ExampleNoise ExampleConvert NF of Convert NF of 4 4 & & 44..1 1 dB to Te with K=dB to Te with K=300300K.K.

Sol.Sol.[NF]=[NF]=4 4 dB dB F=F=22..512512[NF]=[NF]=44..1 1 F=F=22..5757

Te=Te=300300((22..512512--11)=)=453453..6 6 KKTe=Te=300300((22..5757--11)=)=471 471 KK

Note that a Note that a 00..1 1 dBdB difference in [NF] led to a difference in [NF] led to a 1717..44oo difference in Tedifference in Te

Antenna NoiseAntenna NoiseRX antennas (ES and Sat.) introduce noise into the RX antennas (ES and Sat.) introduce noise into the system!!!!system!!!!

Antenna Noise is also dependent on the angle Antenna Noise is also dependent on the angle of elevationof elevation

Types: Types: 11) Self Antenna Noise) Self Antenna Noise22) Sky Noise) Sky Noise

Typical Example: Typical Example: 11-- ES Large CES Large C--band = band = 60 60 KK22-- ES Ku (clear sky)= ES Ku (clear sky)= 80 80 K K 33-- Sat. ant. = Sat. ant. = 290 290 K (Why High?!)K (Why High?!)

Antenna NoiseAntenna Noise

Antenna NoiseAntenna Noise

Rain FadingRain Fading

Rain attenuation is more Rain attenuation is more serious at higher frequencies serious at higher frequencies (C, Ku, Ka,….)(C, Ku, Ka,….)

Rain Information are Rain Information are available in the forms of available in the forms of curves and tablescurves and tables

Rain FadingRain Fading

The Effective Noise Temperature of Rain:The Effective Noise Temperature of Rain:

The Total SkyThe Total Sky--noise Temperature: noise Temperature:

rainCSsky TTT

A1-1TT arain

AA-- Rain attenuationRain attenuationTaTa-- Apparent absorber temperatureApparent absorber temperature

ExampleExampleUnder clear sky conditions, [C/N] is Under clear sky conditions, [C/N] is 20 20 dB, the dB, the total effective noise is total effective noise is 400400K. If rain attenuation K. If rain attenuation exceeds exceeds 11..9 9 dB for dB for 00..1 1 % of the time, then % of the time, then calculate the value below which [C/N] falls for calculate the value below which [C/N] falls for 00..11% given Ta=% given Ta=280280K.K.Sol. :Sol. :11..99 11..5555Tant=Tant=280280((11--11//11..5555)=)=9999..2 2 KKTs=[Ts=[499499..22]]--[[400400]=]=00..96 96 dBdB[C/N]=[C/N]=2020--11..99--00..9696==1717..14 14 dBdB

Satellite System ParametersSatellite System Parameters

btb .TPE

88. Transmit Power (Pt) and Bit Energy (Eb). Transmit Power (Pt) and Bit Energy (Eb)

The Energy per bit (EThe Energy per bit (Ebb) having P) having Ptt at saturation at saturation and bit duration of Tand bit duration of Tbb::

b

tb f

PE

In terms of the bit rate fIn terms of the bit rate fbb==11/T/Tbb , E, Eb b is:is:

Satellite System ParametersSatellite System Parameters

[No][C]]NC[

KTC

NC

oo

99. Carrier. Carrier--toto--Noise Density Ratio (C/No)Noise Density Ratio (C/No) C/No is the average wideband carrier powerC/No is the average wideband carrier power--

toto--noise density ratio:noise density ratio:

]fB[]

NC[]

NE[

NfCB

BNf

C

NE

bo

b

bb

b

o

b

1010. Bit Energy. Bit Energy--toto--Noise Density Ratio Noise Density Ratio (E(Ebb/N/Noo)) EEbb/No is a convenient method to compare /No is a convenient method to compare digital systems using different mod. Schemes!:digital systems using different mod. Schemes!:

Satellite System ParametersSatellite System Parameters

e

LNAant

e TGG

TG

1111. Gain. Gain--toto--Equivalent Noise Temperature Equivalent Noise Temperature Ratio (G/Te)Ratio (G/Te)

G/Te is a figure of merit used to represent an G/Te is a figure of merit used to represent an ES or Sat. RX:ES or Sat. RX:

For a transponder GFor a transponder Gantant==12 12 dB, GdB, GLNALNA==10 10 dB and Te=dB and Te=26 26 dBK, then its G/Te figure of merit:dBK, then its G/Te figure of merit:

][T-][G][G]TG[ eLNAantdB/Ke

G/Te=G/Te=1212++1010--2626==--4 4 dBKdBK--11

Satellite UpLink EquationSatellite UpLink Equation

HPAHPAPt +Pt +LLbobo LLbb

LNALNALbLb G/TeG/Te ...... ……

LLff

PPr=r=EIRPEIRP

LLPP, L, Luu, AML,PL, AML,PL

GGantant

GGsantsant

LLsfsf

e

satbobfLNAsantupESbobfinant

KTLLGGLLLLPG )..(.)().(

NC

o

Satellite UpLink EquationSatellite UpLink Equation

)1().(.).(NC

o KLL

TGGLLLLPG satbobfe

LNAsantupESbobfinant

)(10][][][][]NC[

o

KLogLLTGEIRP upe

0)()( satbosatbf LL

Note: The downlink equation can be easily Note: The downlink equation can be easily maniplulated from the uplink equation (by replacing maniplulated from the uplink equation (by replacing ES by Sat)ES by Sat)

Link Budget ExampleLink Budget ExampleComplete the link budget for a satellite system with the Complete the link budget for a satellite system with the

parameters given in table below.parameters given in table below.

Solution: UplinkSolution: Uplink

** [EIRP]=[P[EIRP]=[PTXTX]+[G]+[Gantant]]--[L[Lbobo]]--[L[Lbfbf]=]=[EIRP]=[EIRP]= 1010Log(Log(20002000)+)+6464--33--44==9090 dBWdBW

** C/NoC/No atat SatSat.:.:C/No=C/KTe=(C/Te)C/No=C/KTe=(C/Te)..((11/K)/K) C/Te=C’C/Te=C’..(G/Te)(G/Te)

** CarrierCarrier densitydensity atat SatSat.. antant..[C’]=[EIRP][C’]=[EIRP]--[Lp][Lp]--[Lu][Lu]==9090--206206..55--00..66==--117117..11 dBWdBW..

C/No=C’C/No=C’..(G/Te)(G/Te)..((11/K)/K) [C/No]=[C’]+[G/Te][C/No]=[C’]+[G/Te]--1010log(log(11//11..3838xx1010--2323)=)= [C/No]=[C/No]=--117117..11--55..33 ––((--228228..66)=)=106106..22

Solution: UplinkSolution: Uplink** Eb/No=(C/Eb/No=(C/ff b)/No=(C/No)b)/No=(C/No) .. ((11//ff b)b) [Eb/No]=[C/No][Eb/No]=[C/No]-- 1010Log(Log(ff b)b) [Eb/No]=[Eb/No]=106106..22 –– 1010 Log(Log(120120xx101066)=)=2525..44 dBdB

** C/NC/N forfor aa minimumminimum bandwidthbandwidthC/N=C/N= (Eb(Eb.. ff bb )/(No)/(No..BB )=(Eb/No)/(B/)=(Eb/No)/(B/ff b)b) [C/N]=[Eb/No][C/N]=[Eb/No] -- [B/[B/ff b]b] [C/N][C/N] == 2525..44-- 1010 Log[(Log[(4040xx101066)/()/(120120xx101066)]=)]=3030..22 dBdB

Solution: Downlink Solution: Downlink

** C/NoC/No atat ESES::C/No=C/KTe=(C/Te)C/No=C/KTe=(C/Te)..((11/K)/K) C/Te=C’C/Te=C’..(G/Te)(G/Te)

** CarrierCarrier densitydensity atat ESES antant..[C’]=[EIRP][C’]=[EIRP]--[Lp][Lp]--[Lu][Lu]==4040..22 --205205..66--00..44==--165165..88 dBWdBW..

C/No=C’C/No=C’..(G/Te)(G/Te)..((11/K)/K) [C/No]=[C’]+[G/Te][C/No]=[C’]+[G/Te]--1010log(log(11//11..3838xx1010--2323)=)= [C/No]=[C/No]= --165165..88 ++ 3737..77 ++228228..66==100100..55 dBdB

** [EIRP][EIRP]satsat=[P=[PTXTX]+[G]+[Gantant]]--[L[Lbobo]]--[L[Lbfbf]=]=[EIRP]=[EIRP]= 1010++3030..88--00..11--00..55==4040..22 dBWdBW

Solution: DownlinkSolution: Downlink** Eb/No=(C/Eb/No=(C/ff b)/No=(C/No)b)/No=(C/No) .. ((11//ff b)b) [Eb/No]=[C/No][Eb/No]=[C/No]-- 1010Log(Log(ff b)b) [Eb/No]=[Eb/No]=100100..55 –– 1010 Log(Log(120120xx101066)=)=1919..77 dBdB

** C/NC/N forfor aa minimumminimum bandwidthbandwidthC/N=C/N= (Eb(Eb.. ff bb )/(No)/(No..BB )=(Eb/No)/(B/)=(Eb/No)/(B/ff b)b) [C/N]=[Eb/No][C/N]=[Eb/No] -- [B/[B/ff b]b] [C/N][C/N] == 1919..77 -- 1010 Log[Log[11//33]=]=2424..55 dBdB

Solution: Combined Link BudgetSolution: Combined Link Budget

** TheThe overalloverall energyenergy ofof bitbit--toto--noisenoise densitydensity ratioratio:: [Eb/No][Eb/No]overalloverall=A/B=A/B

A=(Eb/No)A=(Eb/No)upup.. (Eb/No)(Eb/No)downdown

B=B= (Eb/No)(Eb/No)upup ++ (Eb/No)(Eb/No)downdown

A=(A=(346346..77))..((9393..33)) && B=B=346346..77++9393..33(Eb/No)(Eb/No)overalloverall=A/B==A/B=7373..55[Eb/No][Eb/No]overalloverall==1010 Log(Log(7373..55)=)=1818..77 dBdB

Uplink Downlink

1. ES TX output power at saturation, 2000 W 1. Sat. TX output power at saturation, 10 W

2. ES back-off Loss, 3 dB 2. Sat. back-off Loss, 0.1 dB

3. ES branching and feeder losses, 4 dB 3. Sat. branching and feeder losses, 0.5 dB

4. ES antenna gain, 64 dB 4. Sat. antenna gain, 30.8 dB

5. Additional Uplink atmospheric Losses, 0.6 dB 5. Additional Downlink atmospheric Losses, 0.4 dB

6. Satellite RX (G/Te ) ratio (GTR), -5.3 dbK-1 6. ES RX antenna gain , 62 dB37.7

7. Satellite branching and feeder Losses, 0dB 7. ES branching and feeder Losses, 0dB

8. Bit Rate, 120 Mbps 8. ES equivalent noise temperature, 270 K

9. Modulation Scheme, 8PSK 9. ES G/Te, 37.7 dbK-1

10. Free Space Path Loss at 14 GHz, 206.5 dB 10. Free Space Path Loss at 12 GHz, 205.6 dB

Uplink Downlink

1. ES TX output power at saturation, 2000 W

1. Sat. TX output power at saturation, 10dB W

2. ES back-off Loss, 3 dB 2. Sat. back-off Loss, 0.1 dB

3. ES branching and feeder losses, 4 dB

3. Sat. branching and feeder losses, 0.5 dB

4. ES antenna gain, 64 dB 4. Sat. antenna gain, 30.8 dB

5. Additional Uplink atmospheric Losses, 0.6 dB

5. Additional Downlink atmospheric Losses, 0.4 dB

6. Satellite RX (G/Te ) ratio (GTR), -5.3 dbK-1

6. ES RX antenna gain , 62 dB

7. Satellite branching and feeder Losses, 0dB

7. ES branching and feeder Losses, 0dB

8. Bit Rate, 120 Mbps 8. ES equivalent noise temperature, 270 K

9. Modulation Scheme, 8PSK 9. ES G/Te, 37.7 dbK-1

10. Free Space Path Loss at 14 GHz, 206.5 dB

10. Free Space Path Loss at 12 GHz, 205.6 dB