Earth stations are systems that transmit and receive signals to and from satellites. They consist of subsystems like transmitters, receivers, antennas, and tracking equipment. Key parameters that affect earth station performance include transmitter power, antenna gain and efficiency, noise temperature, and local weather conditions. The ratio of antenna gain to noise temperature (G/T ratio) is important, as it determines the strength of the received signal relative to thermal noise. Path loss increases significantly with distance between the earth station and satellite due to signal dispersion over the propagation path. Various factors like operating frequency, elevation angle, polarization, and local meteorology can impact propagation impairments.

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.