These are various parameters to be taken into consideration in satellite communication

1. EARTH STATION
PARAMATERS
JENIL.J

2. What is Earth Station?
 Any transmitting or receiving system which sends or
receives signal to and from satellite
 Earth station is a vital element in any satellite
communication network.
 The function of an earth station is to receive information
from or transmit information to, the satellite network in the
most cost-effective and reliable manner while retaining the
desired signal quality.
 The design of earth station configuration depends upon
many factors and its location

3. Earth Station Subsystems
 Transmitter
 Receiver
 Antenna
 Tracking Equipment

5. ES Parameters:
• Transmitter power
• Choice of frequency
• Gain of antenna
• Antenna efficiency
• Antenna pointing accuracy
• Noise temperature
• Local conditions such as wind, weather etc,
• Polarization
• Propagation losses

6. G/T Ratio:
 G/T is Gain / Noise Temperature
 G/T = Antenna Gain (dB) - System Noise Temperature (dB) [10
Log(Tsys/1°K )]
 Signal at the receiving antenna is increased by the antenna gain
 Subtract out the System Noise Temperature
 Result is signal level with respect to Thermal noise

7. Calculating G/T:
 TSYS = TA + TLNA
 TA is the antenna noise temperature
 TLNA is the LNA noise temperature (Receiver Noise)
 Antenna: TA = 43° K, Gain = 38 dB
 LNA: TLNA = 51° K
TSYS = 43 ° + 51 ° = 94 ° K
 G/T = Antenna Gain (dB) - 10 Log(Tsys/1°K )
 G/T = 38dB –19.7dB = 18.3 dB -

8. Noise:
 There are two main sources of noise in a satellite system:
 Noise arising in the satellite and earth-station equipment
 Noise collected by the satellite and earth-station antennas
 Noise power radiated by the Earth is collected by the side lobes of the earth-
station antenna and the main beam of the satellite antenna.
 Noise power N is related to an equivalent noise temperature by the
expression:
N = k . T . B watts
Where, K is Boltzmann's constant (1.38 x 10-23 J/K)
B is the bandwidth in which the noise is measured (in Hz)

9. Radiated Power:
 EIRP = Transmitter Output Power + Antenna Gain
 EIRP includes the effects of:
1. Antenna Gain
2. Antenna Efficiencies
3. Transmitter Output Power
4. Coupling and Wave guide Losses, Etc.
 Once the EIRP is known, no additional information about the
transmitter is required.
 EIRP information assumes the transmitter is pointed directly at the
receiver -

10. Transmitted Power
 Typical Required EIRP = 42 dBW / 4kHz (Clear Sky)
Determined by the satellite operator
 Assume Signal Bandwidth = 8MHz + 33 dB (with respect to 4kHz) i.e
10Log(8MHz/4kHz)
 For 8MHz the required EIRP = + 75 dBW
 Antenna size
1. 10 Meter antenna @ 6 GHz 53.3 dB of Gain
 Misc Loss = 4 dB
 Pout= +75 dBW -53.3 dB + 4 dB = +25.7dBW
 Required transmitter Pout = 372 Watts

11. Path loss:
 Signal Radiates out from a point Source
 Flux Density is less at receiving antenna as the distance increases
 Path Loss is actually a dispersion of the transmitted signal

12. Calculation of Path loss:
 Path Loss in dB = 10 Log(PL)
 Path Loss is related to Number of Wave Lengths
 Path Loss proportional to (D / λ) 2
 Example
 Frequency: 14GHz
 Lambda (λ) = 0.021429 Meters
 Distance: 22,300 Miles (35,888 kM)
 Path Loss: 206.46 dB

14. Some Effects.,
 Operating frequency
 Antenna Elevation Angle
 Polarization
 ES Altitude
 ES Noise Temperature
 Local Meteorology
 Climate

15.  Operating Frequency.
With the exception of signal attenuation by gaseous absorption
lines, the severity of tropospheric impairments increases with frequency.
 Earth Station Altitude.
Because less of the troposphere is included in paths from higher
altitude sites, impairments are less.
 Earth Station Noise Temperature.
This determines the relative contribution of sky noise
temperature to system noise temperature~ and thus the effect of sky noise on
the downlink signal-to-noise ratio.

16. Antenna Elevation Angle and Polarization.
 The length of the part of the propagation path passing through the
troposphere varies inversely with elevation angle.
 Accordingly, propagation losses, noise, and depolarization also increase with
decreasing elevation angle.
 Rain attenuation is slightly polarization-sensitive.
 Depolarization is also polarization-sensitive, with circular polarization being
the most susceptible.

17. Local Meteorology.
 The amount and nature of the rainfall in the vicinity of the Earth station are
the primary factors in determining the frequency and extent of most
propagation impairments.
 Rain caused impairments depend on the rate of rain fall, so how the rain
tends to fall (thunderstorms versus steady showers) is as important as the
cumulative amount of rainfall.
 The type and extent of cloud cover, and local humidity characteristics are
other meteorological factors that determine the magnitude of propagation
impairments.