Satellite Link Budget
Satellite Link Budget
Q.1) An earth station
antenna has a diameter of 30m has an overall efficiency of 68% and is used to
receive a signal at 4150MHz. At this frequency system noise temperature is 79K
when antenna points at the satellite at the elevation angle of 280.
What is earth station G/T under these conditions? If heavy rain causes the sky
temperature to increase so that the system noise temperature rises to 88K, what
is the new G/T value?
Q.2) Define following terms
i) Kepler’s First Law
ii) Kepler’s Second Law
iii) Geostationary Earth
Orbit
iv) Polar Orbit
v) Low Earth Orbit
Q.3) At input of receiver
received carrier power is 400pW and system noise temperature is 450K. Calculate
carrier to noise ratio. For a bandwidth of 36MHz calculate carrier to noise
density ratio in dBHz.
Q.4) A satellite freq of
11.7GHz is used by satellite located at altitude of 38000km from earth station.
The satellite output power is 200mW and feeds an antenna with 18.9db gain. The
earth station antenna has aperture area of 3.6575 m2 and aperture
efficiency of 50%. Assume overall noise temperature of system to be 1250K.
Calculate EIRP, Gr, path loss and received power.
Q.5) The space shuttle orbits at an altitude of 250 km above the earth’s
surface. The mean earth radius is approximately 6378.14km. Calculate period of
shuttle orbit when the altitude is 250km and orbit is circular.
ยต=3.986 × 105
Q.6) For a satellite system the carrier is
transmitted to satellite, amplified and re-transmitted. Determine received
carrier to noise ratio at ground receiver using following parameters
Uplink EIRP = 90 dB
Uplink loss= -200dB
Satellite noise figure = 5 db
Satellite gain G = 100dB
Uplink Sky temperature = 3000k
Satellite G/T = -40dB
Satellite BW= 1MHz
Downlink Loss = -190 dB
Receiver G/T = 50 dB
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