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Legacy Satellite Systems

Legacy Satellite Systems. COMSTAR TELSTAR WESTAR GALAXY SATCOM ANIK FDMA Analog Transponder architecture SSB/FDM FDM/FM. NASA ACTS (Advanced Communications Technology Satellite) Deployed 1992 3 Fixed beam Antennas (East and West coasts)

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Legacy Satellite Systems

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  1. Legacy Satellite Systems • COMSTAR • TELSTAR • WESTAR • GALAXY • SATCOMANIK • FDMA Analog Transponder architecture • SSB/FDM • FDM/FM

  2. NASA ACTS • (Advanced Communications Technology Satellite) • Deployed 1992 • 3 Fixed beam Antennas (East and West coasts) • 2 Spot beam antennas (Topeka, Cheyenne Wells) • Baseband processing (Spot Beams) • Straight up-conversion (2 Fixed Beams - one fixed Beam switchable) • CONUS coverage • Multibeam Antennas • Rx – 2.2 m @ 30 Ghz • Tx – 3.3 m @ 20 Ghz • 110 M-Baud (w/o FEC) • 55 M-Baud (64 bit frame, Rate ½, length 5 Convolutional FEC)

  3. Geosynchronous Sats • Typical C band parameters • 500 Mhz total BW • 12 Transponders using 36 Mhz /4 Mhzguardbands • Additional 12 transponders using polarization diversity/20 Mhz offsets • Transponder Usage • FDMA: Part of transponder bandwidth is leased by customer for continuous use. • Analog/Digital • TDMA: Entire bandwidth of transponder is leased for allocated time slots • Usually digital only • Timing is critical due to range from different ground stations • CDMA: . . . . • 22,300 mi altitude • 2 degree spacing • C band 6/4 Ghz • Ku band 14/12 Ghz

  4. CDMA(Code division Multiple Access) Spread Spectrum Data @ fPR + + NRZ Data @ fI Recovered NRZ Data @ fI IF A and B are identical and synchronized Pseudo Random Sequence Generator A @fPR >> fI Pseudo Random Sequence Generator B @fPR >> fI

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