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Link BudgetCalculation

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Introduction

A satellite communication link is defined as anEarth station - satellite - Earth stationconnection.

The Earth station - satellite segment is calledthe uplink.

The satellite - Earth station segment is calledthe downlink.

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Introduction

The Earth station design consists of theTransmission Link Design (Link Budget) andthe Transmission System Design.

Link Budgetestablishes the resources neededfor a given service to achieve the performanceobjectives.

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Link Budget Calculation between

the VINASAT satellite and

the Earth Station at Tam Ky, QuangNam

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LinkParameters

* Operation Bandwidth

Link design at Ku-Band, using frequency of14GHz for the uplink and 11GHz for thedownlink.

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LinkParameters

* Earth Station

- Located at 15,20N latitude and 108,30Elongitude.

- The diameter of the antenna (D) is 13m, theaperture efficiency () is 65%

- Transmission power of Earth Station is 300W.

- Earth station antenna height of 7m above sealevel.

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LinkParameters

* Satellite

- Located at 1320E longtitude.

- EIRPs = 50dBW.- Transponder Bandwidth is 36MHz.

- Receiver noise figure F = 4dB.

- Receiver figure of merit(G/T)s = 1dB/

0K

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LinkParameters

* Other suppositions

- Feeder loss LF = 1dB

- Polarization mismatch loss LPOL = 0.5dB

- Antenna misalignment loss 0.9dB

- Rain loss figure = 3.96dB/km, rain height hR =3.208Km

- Tropospheric loss figure 0.02dB/Km- Ambient temperature TX = 300

0K

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Link Budget

- Slant range distance is

where+ Earth station latitude at Tam Ky = 15.20 N+ Ls = 132

0E , Le = 108.30N

Difference in longitude between the earthstation and the satellite is

Le = 1320 108.30 = 23,70

0 = 27.920

e0 Lcos.coscos

)cosrR2Rr(d 0e2

e

2

884.07.23cos2.15coscos00

0

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Link Budget

Distance between VINASAT satellite and Earthstation at Tam Ky is

d=36629.4 km

- Elevation angle of satellite from the Earth station e

where Re = 6378 [km]r = 35768 + 6378 = 42146 [km]

tge = 1.565 e = 57.420

0

e0

esin

r

Rcos

tg

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Link Budget

- Azimuth of the satellite a

A = -59.150

a = 1800 (59.150) = 239.150

- Earth station transmit antenna gain

where = 0.65 ; D = 20m ; fU= 14GHz ; c=3.108m/s

GTe =67.473 [dB]

674.1)2.15sin(

7.23tg

)sin(

LtgtgA

0

0e

2

UTec

Dflog10G

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Uplink Budget

- Earth station transmit power (300W) in dB is

PTe = 24.77 [dBW]

- Equivalent Isotropic Radiated Power of thetransmitting Earth station is

EIRPe = GTe+ PTe = 92.244 [dBW]

- Uplink total loss is

LU = LSPU + LFU + LOU

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Uplink Budget

+ Free-space loss is

+ Rain loss is (LR)U = U.LS [dB]

where LS is the effective path length of the signal

through the rain

At 15,20

N latitude, rain height (adapted from CCIRRecommendation 564) is

hR = 3+ 0.028 =3,028 [km]

hS = 7m = 0,007km ; sine = sin57.420

[dB]206,641)clg(20)df4lg(20L USPU

e

SR

Ssin

hhL

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Uplink Budget

Ls = 3.585kmU = 3.96dB/km

Uplink rain loss is (LR)U= 14.197dB+ Antenna misalignment losses are

LTe = 0.9dB ; LRs = 0.9dB

+ Polarization mismatch loss isLPOL = 0.5dB

+ Loss due to troposphericeffects is

Ltr=0.02 x 15 = 0.3[dB/Km]

(assuming troposphere height at Tam Ky is 15km)

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Uplink Budget

Hence, uplink total loss is

LU = LSPU + LFU + LOU= LSPU + LFU + (LRU + LTe + LRs + LPOL + Ltr)

= 206.641 + 1 + (14.197 + 0.9 + 0.9 + 0.5 + 0.3)= 224.438 [dB]

- Satellite receiver noise temperature

vi F = 4dB ; T0 = 2900K

TRS = 4380K

010

F

RS T)110(T

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Uplink Budget

- Uplink noise temperature is TU = TRS + TAS

where TRS = 4380K ; TAS = 290

0K

TU

= 4380 + 2900 = 7280K

- Satellite receive antenna gain is

GRS= (G/T)S + 10lgTU [dB]

where (G/T)S = 1 dB/0K

GRS= 1 + 10lg728 = 29.62 [dB]

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Uplink Budget

- Satellite received carrier power is

CRS = EIRPe LU + GRS= - 102.574 [dBW]

- Uplink noise power is NU = 10lgkTUB

where k is Boltzmanns constant (1,38.10-23 [J/K])TU equivalent noise temperature (728

0K)

B is the noise bandwidth of the carrier 36MHz

NU = - 124.4 [dBW]

- Uplink carrier-to-noise ratio

(C/N)U = - 102.574 + 124.4 = 21.826 [dBW]

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Downlink budget

- Downlink total loss LD

+ Free-space loss is

(Ltd)D= 20lg(4fDd) 20lgc

= 20lg(4x11.109x36629.4x103)-20lg3.108

= 204.55 dB

+ Downlink rain loss is (LR)D= 14.197dB

+ Polarization mismatch loss is LPOL= 0.5 dB

+ Antenna misalignment losses are

LTs = 0.9 dB ; LRe = 0.9 dB

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Downlink budget

Downlink total loss is

LD = (Ltd)D + (LR)D + LPOL+ LTs + LRe= 204.55 + 14.197 + 0.5 + 0.9 + 0.9

= 221.05 dB

- Earth station receive antenna gain is

where = 0.65; D = 20m; fD= 11GHz; c=3.108m/s

GRe =65.38 dB

2

D

Re c

Df

log10G

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Downlink budget

* Downlink noise calculation

- Space noise temperature is TS = 52.760K

- Rain noise temperature TMWave attenuation caused by rain is

dB3.261010L 42.110/)L(MDR

K275)3.26

11(286)L

11(TT

M

mM

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Downlink budget

- Noise temperature introduced by the loss of thefeeder line is

- Receiver noise temperature TR ~T1 ,where T1 isnoise temperature of the first module of earth stationreceiverLets give TR = 150

oK

- System noise temperature

= 4720

K

K678.77)110(300)1L(TT 1.0F0F

150259.1

678.77

259.1

27576.52T

L

T

L

TTT R

F

F

F

ASsys

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Downlink budget

- System noise power

- Downlink carrier-to-noise ratio (C/N)D

Blog10Tlog10klog10N syssys 61036log10472log106,228

dBW3.126

38.65221.0550GLEIRPC ReDsRe

dBW67,105

dBW63.203.12667.105NC)N/C( sysRED