Satellite Communications System

TOPICS 1. Satellite Orbits 2. Satellite Communications System 3. Satellite Subsystems 4. Earth Stations Communications 5

Satellite Classifications Spinners A spinner satellite uses the angular momentum of its spinning body to provide roll and yaw stabilization. Three-Axis Stabilizers The body remains fixed relative to Earth’s surface while an internal subsystem provides roll and yaw stabilization. Communications 5

Attitude Control ROLL YAW Satellite PITCH Communications 5

Transponder L.N.A. MIXER H.P.A. Rx Tx LOCAL OSCILLATOR Communications 5

Frequency Allocations Uplink (GHz) Downlink (GHz) Bandwidth (MHz) Band C X Ku Ka 5.9 – 6.4 7.9 – 8.4 14 – 14.5 27 – 30 30 – 31 3.7 – 4.2 7.25 – 7.75 11.7 – 12.2 17 – 20 20 – 21 500 ----- Communications 5

Bandwidth Considerations 2 3 4 5 6 7 8 9 10 11 1 12 Each Channel – 36 MHz Guard Band – 4 MHz 3720 3800 3880 3960 4040 4120 3760 3840 3920 4000 4080 4160 5925 MHz 500 MHz Receive Bandwidth Transmit Channels Channel Center Frequencies (MHz) Communications 5

General Block Diagram of Communications Satellite Charger and Batteries Regulators: Protection and Conditioning DC/DC Converter DC/AC Inverter Receiver Frequency Translator Transmitter Antenna Subsystem Telemetry, Tracking, and Control Propulsion Attitude Jet Thruster AKM DC and AC to special subsystem DC to all subsystems Inputs from on-board sensors Solar Panels Communications Antennas Telemetry Antenna Transponder Other Transponders signals to all subsystems Communications Subsystem Communications 5

SINGLE CONVERSION TRANSPONDER LNA MIXER AMPLIFIER BPF HPA fo fi LO Communications 5

Double Conversion Transponder LNA MIXER IF AMPLIFIER BPF HPA fo fIF fi LO Communications 5

Regenerative Transponder LNA MIXER DEMODULATOR MODULATOR HPA BPF LO Baseband Signal Communications 5

Broadband System LNA HPA LO 1 2 n-1 n F2 Fn-1 Fn nB B fi fo COMBINER AMPLIFIER LNA MIXER BPF F1 HPA LO FN COMBINER 1 2 n-1 n F2 Fn-1 Fn nB B fi fo Communications 5

Fully Channelized System Downlink Antenna BPF FN F1 DEMUX LNA MIXER HPA LO COMBINER Uplink Communications 5

Solar Array Configurations Solar cell array on surface Spin-Stabilized Satellite Deployable Solar Panels Central housing or body rotation Body-Stabilized Satellite Communications 5

Earth Stations BPF LNA BPF LO HPA BPF LO Baseband Outputs DEMUX Down Converter BPF Power Divider DEMODULATOR LNA BPF LO Antenna Subsystem Receive Subsystem GCE - Receive Diplexer Carrier Oscillator Transmit Subsystem Up Converter Baseband Inputs MUX Combiner MODULATOR HPA DRIVER BPF LO GCE - Transmit DC power to all subsystems AC power in Power Subsystem Communications 5

Applications Overview Communications act as relay stations in the sky. TV Broadcasting Surveillance or Observation Monitoring for enemies Meteorological Geodetic Global Positioning System (GPS) Communications 5

RECAP Satellite Orbits Earth Stations Applications Overview Communications System Satellite Orbits Satellite Subsystems Next Topic… LINK BUDGET Earth Stations Applications Overview “I much prefer the sharpest criticism of a single intelligent man to the thoughtless approval of the masses.” - Johannes Kepler Communications 5