Calculation of receiver G/T

9.Calculation of receiver G/T

1.Antenna elevation angle (deg) Antenna elevation effects the antenna noise temperature. Antenna noise temperature decreases with increase of elevation.

2.Antenna noise temp Antenna noise temperature is the sum of all noise sources at the antenna.

3.Increase in Antenna noise due to rain Rain effects the antenna noise temperature. It increases the antenna noise temperature.

4.LNA noise temp LNA means Low Noise Amplifier. LNA noise temperature means noise temperature of LNA.

5.System noise temp (k) It is the sum of all noise temperatures at the receiving antenna

System noise temperature (k) = antenna noise temperature + increase in antenna noise due to rain + LNA noise temperature (k)…………….[13]

Example: Calculate system noise temperature of a satellite having noise temperature 25 K increase in antenna noise due to rain =0 K LNA noise temperature = 50 K
Solution
System noise temperature = antenna noise temperature + increase in antenna noise due to rain + LNA noise temperature
= 25 + 0 + 50 = 75

6.Receiver G/T (dB/k) Receiver G/T is the Figure of merit at the receiver antenna.

Receiver G/T (dB/K) = Receiver Antenna gain – 10 log(system noise temperature) (dB/k) …………………….[14]

Example: Calculate Receiver G/T (dB/K) of a satellite having antenna gain 41.33 , over all receiver noise temperature = 75 K
Receiver G/T (dB/K) = Receiver Antenna gain – 10 log(system noise temperature)
= 41.33- 10 log(75)
=22.579 (dB/K)