1
EEE440 – Geostationary Satellite
We lead
Three conditions are required for an orbit to be geostationary
1. Satellite must travel eastward at the same rotation speed as the earth
2. The orbit must be circular
3. The inclination of the orbit must be zero
2
EEE440 – Satellite Operating Frequencies
We lead
Operating Frequencies (approx.)
• It is important to be aware of at what frequencies different services
operate:
– VHF:
100 - 300 MHz (little LEOs)
– L-band: 1.5/1.6 GHz (Mobile Satellite)
– S-band: 2 GHz (satellite UMTS)
– C-band: 4 - 8 GHz (Fixed links)
– Ku-band: 12 - 18 GHz (VSAT links)
– Ka-band: 27 - 40 GHz (Broadband Multimedia)
3
EEE440 – Antennas (Geostationary sattelite)
We lead
• Transmitting antennas are used to focus
power into a particular wanted direction
• Receiving antennas are used to receive
transmissions from a particular direction
• The orientation of an antenna is determined
by its elevation and azimuth
4
EEE440 – Antennas (Elevation & Azimuth Angles)
We lead
5
EEE440 – Look Angles (Geostationary satellite)
We lead
1. Earth station latitude - 𝜆𝐸
2. Earth-station longitude - 𝜙𝐸
3. Subsatellite point longitude - 𝜙𝑆𝑆
6
EEE440 – Look Angles (Geostationary satellite)
We lead
7
EEE440 – Look Angles (Geostationary satellite)
We lead
𝑎 = 90𝑜
𝑐 = 90𝑜 − 𝜆𝐸
𝐵 = 𝜙𝐸 - 𝜙𝑆𝑆
Napier’s rule:
𝑏 = cos −1 cos 𝐵 cos 𝜆𝐸
𝐴 = sin−1
sin 𝐵
sin 𝑏
8
EEE440 – Look Angles (Geostationary satellite)
We lead
9
EEE440 – Look Angles (Geostationary satellite)
We lead
Example 1:
A geostationary satellite is located at 90oW. Calculate the
azimuth angle for an earth-station antenna at latitude
35oN and longitude 100oW.
10
EEE440 – Look Angles (Geostationary satellite)
We lead
Example 2:
A geostationary satellite is located at 90oW. Calculate the
range and antenna elevation angle for an earth-station
antenna at latitude 35oN and longitude 100oW.
11
EEE440 – Look Angles (Geostationary satellite)
We lead
12