The transmission frequency is 6.25GHz and receiving frequency is 4.5 GHz. System noise temperature is 140 K. Find EIRP and G/T ratio.

Subject : Satellite Communication and Network

Topic: Satellite Links

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 = $Gt = \eta (10.472 f D)^2$

Where $\eta$ = antenna radiation efficiency = 0.55 (Assumption)

f = frequency in GHz

D = diameter of antenna in meter

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

$\text{Gt in Decibel} = [Gt] = 10 \ log (58900.900) = 47.70 dB $

$ 2EIRP = \frac{PtGt}{4 \pi r^2} = \frac{100 \times 58900.90 }{4×π×(35786×103)^2} $

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

$2EIRP = 36.6 n W/m^2$

$G/T =Gr/T = \frac{58900.90}{140} = 420.72$

$G/T \text{ in decibel} = [G/T] =10 \ log (420.72) = 26.23 dB$

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 = 6.25 GHz.