Mumbai University > EXTC > Sem 8 > Satellite Communication and Networks

Marks: 10M

An earth station employs a power amplifier providing an output power of 100W and an antenna of 5m diameter for both transmission and reception. The transmission frequency is 6.25 GHz and receiving frequency is 4.5GHz. System noise temperature is 140K. Find EIRP and G/T ratio.

Data:

Output power Pt =100 W

Diameter of transmitter antenna =5m

Diameter of receiver antenna =5m

Transmission frequency = 6.25GHz

System noise temeperature =140 K

To find: EIRP (Equivalent/Effective Isotropic Radiated Power), G/T Ratio

Solution:

Gain of transmitter antenna = Gt = η (10.472 f D)2

Where η =antenna radiation efficiency = 0.55 (Assumption)

f= frequency in GHz

D = diameter of antenna in meter

Gt = 0.55 (10.472 × 6.25 × 5)2 = 58900.90

Gt in Decibel =[Gt] =10 log (58900.900 =47.70 dB)

$2EIRP = PtGt / 4πr^2$

$= 100 × 58900.90/[4 × π × (35786 × 10^3)^2]$

{Assumption r =35786 km = height of geostationary satellite}

= 36.6 nW/m2

G/T = Gr/T = 58900.90/140 = 420.72

G/T in decibel = [G/T] =10 log (420.72) = 26.23 dB

Note: In this numerical the receiving frequency 4.5 GHz is mentioned but G/T ratio is always calculated at satellite antenna where the received frequency is same as transmitting frequency = 6.25GHz.