CNR CNOR lecture55 satellite technology and prpagation 2024.ppt

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1. Satellite link budget
The performance measures used in a satellite link budget is eitherC/NorC/N
o
Carrier to Noise Ratio (C/N)
The ratio of carrier power P
R to noise power P
N at the receiver input.
it is denoted by C/N(or CNR or P
R / P
N).
In terms of decibels: [C/N] = [P
R] –[P
N]
Carrier to Noise power density Ratio (C/N
o)
The ratio of carrier power P
R to noise power density N
o
it is denoted by C/ N
o(or P
R / N
o) in terms of dB Hz.
Since P
N=N= k T
NB
Nand[N] = [K] +[T
N]+ [B
N]
N
o= KT
N and[No] = [K] +[T
N]

2. The C/No or C/N ratio in terms of EIRP
The received power is given by
[P
R] = [C]=[EIRP]+ [G
R]-[total Losses]
where:[EIRP]iseffectiveisotropicradiatedpower.[G
R]isreceiver
antennagain.[totalLosses]=[FSL]+[RFL]+[AML]+[AA]+[PL]
[P
N] is the noise power
[P
N] =[N]= [K]+[T
N]+[B
N]
Where:T
Nisequivalentnoisetemperature.B
Nisequivalentnoise
bandwidth.KisBoltzmann’sconstant=-228.6decilogsrelativetoone
jouleperKelvin.K=1.38X10^-23J/K
N
o=KT
N is the noise power spectral density.
[N
o]= [K]+[T
N]

3. The down link C/No ratio in terms of EIRP
Thedownlinkofasatelliteinwhichthesatelliteistransmittingthe
signalandtheearthstation(ES)isreceivingit.
Thecarriertonoisepowerdensityratio[C/No]Dindownlinkwhere
subscriptDdenotesthatthedownlinkisbeingconsidered.
Thus[C/N
o]
DEquationbecomes:
[C/N
o]
D= [EIRP]
Dsat-[Total Losses]
D+ [G/T]
D
ES-[K]
where
[EIRP]
Dsatis the satellite effective isotropic radiated power.
[G/T]
D
ES is the earth station(ES) receiver figure of merit .
[Total Losses]
Dis the total losses that include free space loss(FSL) ,
the earth station receiver feeder losses (RFL) and other losses .
K is Boltzmann’s constant is equals -228.6 decilogsrelative to one
joule per Kelvin.

4. The down link C/N ratio in terms of EIRP
The carrier-to-noise ratio, [C/N]
DEquation becomes, assuming the
signal bandwidth B and the noise bandwidth B
N:
[C/N]
D=[EIRP]
Dsat -[total Losses]
D+ [G/T]
D
ES–[K] –[B]
where
B is the signal bandwidth in Hz.

5. Up link budget analysis

6. The Uplink C/No ratio in terms of EIRP
The uplink (UL )in which the earth station(ES) is transmitting the signal
and the satellite is receiving it.
The carrier to noise power density ratio [C/No]u in uplink where
subscript Udenotes uplink. Thus [C/No]
Uequation is as follows:
[C/No]
U= [EIRP]
ES-[total Losses]
U+ [G/T] sat –[K]
where
[EIRP]
ES earth station effective isotropic radiated power
[G/T]
satis satellite receiver figure of merit G/T.
[total Losses]
Uis the total losses that includes free space loss (FSL)
,satellite receiver feeder losses (RFL) and other losses.

7. Saturation flux density (SFD) definition

8. The up link C/No ratio in terms of SFD

9. Effective area versus physical aperture area of the
antenna
•For apertures antennas, such as parabolic reflector types, the effective
area of aperture is related in a direct way to the physical area of aperture.
•If the wave is uniformly illuminate the physical area of aperture, then the
physical area of aperture will be equal to the effective area of aperture.
•If the field of the incoming wave alters the field distribution, thereby
preventing uniform illumination. The effective area of aperture is smaller
than the physical area of aperture by a factor known as the aperture
illumination efficiency.
•A typical value for aperture illumination efficiency is 0.55, although values
as high as 0.73 have been specified.

10. The up link C/No ratio in terms of SFD

11. The up link C/N ratio in terms of SFD

12. Combined Uplink and Downlink carrier to noise (C/N)Ratio

13. Combined Uplink and Downlink carrier to noise (C/N)Ratio
The noise power per unit bandwidth by P
NU
The average carrier at the same point by P
RU
The carrier to noise ratio on the uplink is
(C/No)
U= (P
RU/P
NU).
The carrier power at the end of the space link is P
R
which is also the received carrier power for the downlink and is equal
to times the carrier power input at the satellite, where is the
system power gain from satellite input to earth station input.

14. Combined Uplink and Downlink carrier to noise (C/N)Ratio
•The carrier to noise power spectral density (C/N
o) ratio for the
downlink not counting the P
NUcontribution, is P
R/P
ND, .
•The combined carrier to noise power spectral density (C/N
o)ratio at
the ground receiver isP
R/(P
NU+ P
ND).

15. Combined Uplink and Downlink carrier to noise (C/N)Ratio
The uplink value by (N
o/C)
U
The downlink value by (N
o/C)
D
The combined noise power density to carrier ratio value by N
o/C
N
o/C = P
N/ P
R
= P
NU+ P
ND/ P
R
= P
NU/P
R+ P
ND/P
R
(N
o/C)
combined= (No/C)
U+ (No/C)
D

16. Combined Uplink and Downlink carrier to noise (C/N)Ratio
If the inter modulation is (C/No)
IMis taken into consideration
Equation becomes
(No/C)
combined= (No/C)
U+ (No/C)
D+ (No/C)
IM
Steps for calculation of [C/No]
combined
•Given [C/No]
U, [C/No]
Dand [C/No]
IM
•Calculate: (No/C)
U=10^-[C/N]
U
(No/C)
D=10^-[C/N]
D
(No/C)
IM=10^-[C/N]
IM.
•(No/C)
combined= (No/C)
U+ (No/C)
D+ (No/C)
IM
•[C/No]
combined= -10 log (No/C)
combined

17. Combined Uplink and Downlink carrier to noise (C/N)Ratio

18. Back off [BO]

19. Back off [BO]
Input back off [BO]
i
Whenanumberofcarriersarepresentsimultaneouslyina
travellingwavetubepoweramplifier(TWTPA),theoperating
pointmustbebackedofftoalinearportionofthetransfer
characteristictoreducetheeffectsofintermodulationdistortion.
multiplecarrieroperationoccursinfrequencydivisionmultiple
accesses(FDMA).
The back off must be taken into account in the link budget
calculations.

20. Back off [BO]
Input back off [BO]
i
Input back off in multiple carrier (MC) operation, referred to the single
carrier (SC) saturation level. The earth station EIRP is reduced by back off
(BO), resulting uplink value
[EIRP]
U= [EIRP
s]
U–[IBO]
Although some control of the input to the transponder power amplifier is
possible via telemetry tracking and control (TT&C) station.
input back off is achieved through reduction of the [EIRP] of the earth
stations accessing the transponder.
Thus, equation becomes
[C/N
O]
U=[ ] +[A
O] -[BO]
i-[RFL] + [G/T]
U–[K]

21. Back off [BO]
Output back off [BO]
o
Whereinputbackoffisemployed,acorrespondingoutputbackoffinthe
satelliteeffectiveisotropicradiatedpower(EIRP).Outputback-offisnot
linearlyrelatedtoinputbackoff.theoutputbackoffis5dBbelowthe
extrapolatedlinearportion.
The relationship between input and output back off is as follows:
[BO]
o= [BO]
i-5 dB.
If the satellite EIRP for saturation conditions is specified as [EIRP
S]
D. Then
[EIRP]
D= [EIRP
S]
D-[BO]
o
Thus, equation becomes
[C/N
O]
D=[EIRP
S]
D-[BO]
o-[total Losses]
D+ [G/T]
D–[K]