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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 - 2. Earth-station longitude - 3. Subsatellite point longitude - 6 EEE440 – Look Angles (Geostationary satellite) We lead 7 EEE440 – Look Angles (Geostationary satellite) We lead = 90 = 90 − = - Napier’s rule: = cos −1 cos cos = sin−1 sin sin 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