ch3 link analysis

7/30/2019 CH3 Link Analysis

1/31

SatelliteLinkDesi n

R.N.Mutagi

ElectronicsandCommunicationEngineeringDepartmentn us ns u eo ec no ogyan ng neer ng


2/31


3/31

po n source n space

transmitting powerPtwatts

in all the directions, alon 4

radians of a sphere is called

an isotropic radiator

.

The flux density in unit area

(1 m2) at a distance R

me ers rom s source s

2

2W/m

PF t=


4/31

A practical antenna radiates P0watts of total power thepower radiated in unit solid angle in the direction is P().

If this power is transmitted by an ideal isotropic radiator

the power transmitted along unit solid angle would be

P /4W/m2.

The gain of the practical antenna is therefore

directioninantennapracticalbydtransmittePower

directionsameinradiatorisotropicbydtransmittePower

4/

)(

0P

G =


5/31

e power ra a e y an an enna a ong e ore s g

is the maximum


6/31

Antenna gain depends of the ability of the antenna to concentrate

the energy in particular direction

hwavelen tisandareaa erturetheiswhere4

AA

G

=

An effective aperture areaAe = AA, is defined to account for theA

22

4

4 eA

AAG ==

For a circular parabolic dishA=D2/4, where D is diameter

2

2A2

===

G

AA


7/31

sa e e rece v ng s a on as a s an enna w an

aperture area of 7.5 m2. It receives a signal at 4.2GHz. If

the a erture efficienc is assumed to be 70% find the

gain of the antenna. If the service is switched to Ku band

and the new frequency of reception is 11.5 GHz find the.


8/31

=2

G AAntenna gain is given by

We have A=7.5 m2, =0.7 and

=c/f=3x108/4.2x109=0.071m

dBdBG 12.41)12941log(10129410714.0

.7.0

2===

=

For 11.5 GHz the wavelength is =3x108/11.5x109=0.026m

dBidBG 89.49)97594log(1097594

026.0

.7.0

2===

=


9/31

reateanequat ontoca cu atet eantennaga n n w enfrequency

in

GHz

and

diameter

in

meter

are

given

2

=

G A

/

2

=c

DG A

16054.9180lo20lo2094.9lo10

)103log(20)10log(20log20log20log10 89

++++=

+++=

D

fDG AdB

4.20log20log20log10++=

fDA


10/31

or a ransm er ransm ng power t a s w an

antenna gain Gt the EIRP is defined as

ttGPEIRP=

2W/mGP

F tt=


11/31


12/31

4 eA r

effectivearea

si nalwavelen th

2

r =

Foragivenantennathegainishigherfor

higher

frequency

TxPin

EIRP

R

FRx

Pr

Prad

t r

( ) 22 GGPEIRP rtrad

12

22 4444 =

==

RRRrtrader


13/31

- ,

expansion of the spherical wave front as the wave

.

22

44 == fRR c

p

losspathspacefreewhere =Lp

(Hz)frequency

(m)distance

==

f

R

m/s)10(3space-freeinlightofvelocityc8

=

=


14/31

orageostat onarysate teca cu atet e reespace oss n

dBfor

the

signal

received

on

ground

at

frequencies

4GHz

and11GHz

Create

an

equation

for

measuring

free

space

loss

in

dB

when

22

=

=c

Lp


15/31

2 += LGEIRPP

4 = RGGPPrtradr

(dBW)powerreceived=Where Pr

4

2

== R

tt

p

Considering atmospheric attenuation, La, Transmit Antennalosses Lta, receiving antenna losses Lra we can write

dBWrataaprr

LLLLGEIRPP +=


16/31

o ec s a p ys ca empera ure n >o genera e

electrical noise at receiver frequencies. The noise poweris iven b

Pn = N0B = kTnB

n

N0 is noise power spectral density in W/Hz

k is Boltzmanns constant =1.38 x 10-23 J/K

=-228.6 dBW/K/Hz

Tn is system noise temperature in0K(0C+273)

Fall2008 16

B is the system noise bandwidth in Hz


17/31

Ideal IFIdealIdeal RF

Pn

amplifiermixeramp er

Gain

GRF

Gain

G

Gain

GTin

TRF

TM TIF

Gain E uivalent

GRF.GM.GIF ns system

R.N.Mutagi ELN5597 17

)( inRFMIFRFMMIFIFIF TTkBGGGBkTGGBkTGPn +++=


18/31

TTkBkTkTPn +++=

inRFMIF

IFMIF

n

TTG

T

GG

TkBGGG

+++= )(

SIFMIF kBTGGG=

TS isthesingleequivalentnoisetemperatureproducingsame

noisepower

+++= )( inRFMIF

S TTTT

TRFRFM


19/31

an rece ver assu systemsw t o ow ng

specifications

dBGKT MRF

RFin

350

==

==

KTIF

IFM

1000

=

a cu atet e

system

no se

temperature


20/31

+++= )( inRFRF

M

RFM

IFS TT

GT

GGTT dBGKT

dBGKT

MRF

RFin

5.0350

2002350

===

===

KT

dBGKT

IF

IFM

1000

100030500

=

===

5001000 S

1005.210

2002005.0

++=

K5.112=


21/31

andis

defined

as

( )in

NS Si/Ni

Anamplifier

will

add

its

own

noise

and

the

output

S/N

will

be

( )out

NSo o

lowerthaninputS/N

( )AAiiiii NNANNSNS +/

( ) iiAiioo ANANNANASNS +/

,


22/31

e re a on e ween no se gure an no se empera ure

is give by

Where T0

is the reference noise temperature = 290K

0 =d

Example, for an amplifier with noise figure of 3 dB the noise

empera ure s

( ) KTd 29012290 ==


23/31

e carr er o no se ra o a e rece ver npu s

===

S

rtt

S

rtt

T

G

RkB

GP

BkT

RGGP

powerNoise

powerSignal

N

C2

4

4

The terms in first bracket depend on the satellite

parame ers an ose n e secon epen on ereceiving earth station

r Scalled the Figure of Merit of the earth station


24/31

n ear s a on as an an enna o m ame er an

has an efficiency of 65%. The system noise temperatureof 80K. The receive fre uenc is 4GHz. Find the G/T

ratio of the earth station.

DG Ar 256609

104/103

1565.0

2

98

2

=

=

=

TS 80

==

=

Sr


25/31

equation

dBW+= LLLLGEIRPP

sationearthofeirp

=

raaaprr

EIRP

frequencyuplinkatlosspath=

=

p

r

L

lossantennasatellite

lossantennastationearth

==

ra

ta

L

L

lossescatmospheri=aL

( ) ( )


26/31

( ) ( ){ {

UL

M

UL

p

Sat

sr

ESSat

ULLLTGEIRPNC ++= 6.228// 0

43421321

43421

( ) ( ) MpSrUL LLTGEIRPNC ++= 3214341

3214341

6.228// 0ULkULSat

ESSatelliteat

AlltermsareexpressedindB

Thelasttermincludesalltheantennalosses,

atmosphericattenuation

loss

and

also

any

other

marginrequired(likerainfadingmargin)


27/31

e sa e e n cons s s o up n an own n

In a frequency translation type transponder the downlinkis affected b the u link

The total C/N received is given by

111

+

=

DLUL NNN

If (C/N)UL>> (C/N)DL then the link is downlink limited, else

it is uplink limited


28/31

In addition to thermal noise interference si nals within

the band also impair the carrier

The total uplink noise power isth

+= k kuINN

k

11111

+

=

+

=

CCCCC

Similarly for downlink

UUkUUL

11111 CCCCC

Overall satellite link is

=

=

DDk kDDL ININN

1

+

+

+

=

DUDUTotal I

C

I

C

N

C

N

C

N

C


29/31

sate tetransm ts s gna n u an Transmit

frequency

12

GHz

Transmit oweris 160W

gainofsatelliteantennais35dBi ontheboresight.

Receiveantennagainis33dBi .

Thereceivesystemnoisetemperatureis145K Signalbandwidthis20MHz.

Calculate theC/Natthereceiverandthelinkmarginifthe

demodulatorrequiresaminimumC/Nof10dB.


30/31

rataaprr ==

====

4422

=

=fRR

L

lo20lo204

lo20 ++

= RdBL

c

)000,000,36log(20)1012log(206.147103

9 ++=

13.20513.311206.211806.147 =++++=


31/31

= - . - + =- .

N=k(dB)+Ts(dB)+B(dB)= -228.6+10lo 145+10lo 20x106

= -228.6 + 21.61 + 70+3

= -133.99

C/N dB = -116.13 (-133.99) = 17.86 dB

arg n = va a e res o= 17.86 10 = 7.86 dB

ch3 link analysis

Documents