Wireless Communications ECE 442
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This 8 page Class Notes was uploaded by Roel Green on Wednesday September 23, 2015. The Class Notes belongs to ECE 442 at University of New Mexico taught by Sudharman Jayaweera in Fall. Since its upload, it has received 40 views. For similar materials see /class/212145/ece-442-university-of-new-mexico in Engineering Electrical & Compu at University of New Mexico.
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Date Created: 09/23/15
ECE442 Wireless Communications Lecture 12 Mobile Satellite Systems Prof Sudharman K Jayaweera Department of Electrical and Computer Engineering University of New Mexico A Brief History of Satellite Systems 9 9 0 1945 Sir Arthur C Clarke publishes his essay titled Extra Terrestrial Relays 1957 First satellite called Sputnik is launched 1960 First reflecting communication satellite Echo is launched 1963 First geo stationary satellite Syncom is launched 1965 First commercial geo stationary satellite Early Bird lnteksat l 1982 First mobile satellite system lnmarsat A is launched 1988 lnmarsat C becomes the first satellite system for both mobile phones and data communication 1993 First digital satellite telephone system 1998 Global satellite systems for small mobile phones I l Satellite Orbits o The placement and orbiting shapes of satellites depend on the specific requirements of the particular application 0 Accordingly 4 different types of satellite orbits can be identified GEO geo stationary earth orbit at about 35786km above the earth39s surface LEO lowearth orbit at about 500 1500km above the earth39s surface MEO mediumearth orbit or ICO intermediate circular orbit at about 600020000km above the earth39s surface HEO higth elliptical orbit Satellite Orbits GEO Inmersat MEO ICO 9 LEO Globalstar Irdium 31768 km Figure 111 Orbits of different satellites From Textbook Orbital Frequency of a Satellite 0 There is a relationship between the radius of the satellite orbit r and its orbital frequency f o For a circular orbit it is given by gl i 2 27 where g is the gravitational acceleration of the earth g 981m52 and R is the radius of the earth R 6370 km l l Frequency Bands for Satellite Communications Satellites operate at different frequencies for the uplink MS to satellite and downlink satellite to MS Satellite Frequency Bands 0 The first generation satellites were operated in C band a This band is overcrowded since terrestrial microwave networks have begun using frequencies in this band 0 Currently the Ku and Ka bands are becoming popular 0 But significant rain attenuation is a concern in these bands