Uplink, Downlinkperformance intersatellite communication

1. UPLINK, DOWNLINK
AND
OVERALL LINK
PERFORMANCE
INTERSATELLITE LINKS
ENG : AHMED AYMAN FAHMY

2. AGENDA
• Configuration of the link
• Antenna parameters
• Radiated power
• Received signal power
• Individual link performance
• Influence of the atmosphere
• Mitigation of atmospheric Impairments

3. TYPES OF LINKS
• Uplinks from the earth stations to the satellites.
• Downlinks from the satellites to the earth
stations.
• Intersatellite links between the satellites.

4. CONFIGURATION OF THE LINK
• The satellite communications link EIRP = 𝑷 𝑻 𝑮 𝑻

5. ANTENNA PARAMETERS
1. Gain :
• The gain of an antenna is the ratio of the power radiated (or received) per unit solid
angle by the antenna in a given direction to the power radiated (or received) per unit
solid angle by an isotropic antenna fed with the same power.
• The gain is maximum in the direction of maximum radiation (the electromagnetic
axis of the antenna).
𝑨 𝒆𝒇𝒇 is the effective
aperture area of the
antenna

6. ANTENNA PARAMETERS (GAIN)
• For an antenna with a circular aperture or reflector of diameter D and geometric surface
A = 𝜋𝐷2/4
𝑨 𝒆𝒇𝒇 = ƞ A
• where ƞ is the efficiency of the antenna

7. ANTENNA PARAMETERS
2. Radiation pattern and angular beamwidth
• The radiation pattern indicates the variations of gain with direction.

8. ANTENNA PARAMETERS (BEAMWIDTH)
• The angular beamwidth is the angle defined by the directions
corresponding to a given gain fallout with respect to the maximum value.
• The 3 dB beamwidth corresponds to the angle between the directions in
which the gain falls to half its maximum value .

9. • If ƞ = 0.6
ANTENNA PARAMETERS (BEAMWIDTH)

10. ANTENNA PARAMETERS
3. Polarization : the polarization of the wave is defined by the direction of
the electric field

11. ANTENNA PARAMETERS (POLARIZATION)
• Polarization is characterized by the following parameters:
• direction of rotation : clockwise or counter-clockwise.
• axial ratio : that is the ratio of the major and minor axes of the ellipse
When the ellipse is a circle the polarization is said to be circular. When
the ellipse reduces to one axis the polarization is said to be linear
• inclination 𝜏 of the ellipse.

12. RADIATED POWER
1. Effective isotropic radiated power (EIRP)
• The power radiated per unit solid angle by an isotropic antenna fed from a
radio frequency source of power 𝑃 𝑇 is given by
• In a direction where the value of transmission gain is 𝐺 𝑇
EIRP = 𝑷 𝑻 𝑮 𝑻

13. 2. Power flux density
• A surface of area A situated at a distance R from the transmitting antenna
subtends a solid angle A/𝑅2
at the transmitting antenna . It receives a power
equal to:
• The magnitude of Ф = 𝑃 𝑇 𝐺 𝑇/4𝜋𝑅2 is called power flux density.
RADIATED POWER

14. RADIATED POWER
• Received Signal Power