Gateway to Amateur Satellites for Internet Users By Bo, Junsang, Suresh, Vinh http://www.livemotion.us http://www.livemotion.us CE3992
Gateway to Amateur Satellites for Internet Users Gateway to Amateur Satellites for Internet Users HISTORY: Beginning HISTORY HISTORY First milestone SATELLITE SPECS ANTENNA SYSTEM - The first satellite was Sputnik I by Soviets. The first PRE AMPLIFICATION successful United States launch took place four months ROTATOR CONTROLLER after launching Sputnik I. MODEM/TNC SOFTWARE Second milestone POWER SYSTEM BACKUP PLAN - SCORE: often referred to as first comsat. However, it TIMELINE carried only a taped message for playback. It could not be OBSTICLES used for relaying signals. QUESTION Now over 2500 satellites on the sky… CE3992
Gateway to Amateur Satellites for Internet Users Gateway to Amateur Satellites for Internet Users HISTORY: Beginning Amateur Satellites HISTORY HISTORY OSCAR 5 SATELLITE SPECS ANTENNA SYSTEM - It is called AO-5( Australia's - OSCAR 5 ) PRE AMPLIFICATION . Built by several students at the University of ROTATOR CONTROLLER Melbourne, most undergraduate engineering major for 3 years. However, it was not launched. MODEM/TNC SOFTWARE POWER SYSTEM AMSAT( the Radio Amateur Satellite Corporation ) BACKUP PLAN TIMELINE . AMSAT was formed in order to support AO-5, . OBSTICLES Finally, AO-5 was launched on March 3 rd , 1969. QUESTION CE3992
Gateway to Amateur Satellites for Internet Users Gateway to Amateur Satellites for Internet Users SAT SPEC: Operation modes HISTORY Analog Communication Mode( CW & SSB ) SATELLITE SPECS SATELLITE SPECS ANTENNA SYSTEM • Linear mode – receives a slice of one amateur band PRE AMPLIFICATION PRE AMPLIFICATION and shifts the entire slice to a different band. ROTATOR CONTROLLER • Real time communication ( use voice ) MODEM/TNC Digital Communication Mode( FSK & PSK ) SOFTWARE POWER SYSTEM • Non linear mode – these vary in speed and in the BACKUP PLAN modulation techniques employed. TIMELINE • Not real time – store & forward communication ( use OBSTICLES software ) QUESTION Special Modes( Repeater, Broadcast, ROBOT etc… ) CE3992
Gateway to Amateur Satellites for Internet Users Gateway to Amateur Satellites for Internet Users SAT SPEC: Orbits HISTORY Low Earth Orbit( LEO ) SATELLITE SPECS SATELLITE SPECS • Could be accessed with low power and simple antennas. ANTENNA SYSTEM • They generally used lower frequencies for which PRE AMPLIFICATION PRE AMPLIFICATION transmitting and receiving equipment is widely available. ROTATOR CONTROLLER • Limited communication time( usually less than 20 minutes per day ) MODEM/TNC SOFTWARE High Earth Orbit( HEO ) POWER SYSTEM • Need high power, beam antennas and very sensitive BACKUP PLAN receivers. TIMELINE • Biggest obstacle communicating with these satellites is OBSTICLES the high frequency being used (antenna precision) • Longer communication time QUESTION CE3992
Gateway to Amateur Satellites for Internet Users Gateway to Amateur Satellites for Internet Users SAT SPECS: Target Satellites HISTORY Digital Communication Mode( FSK & PSK ) SATELLITE SPECS SATELLITE SPECS • 1200 bps & 9600 bps ANTENNA SYSTEM • software base PRE AMPLIFICATION PRE AMPLIFICATION ROTATOR CONTROLLER Low Earth Orbit( LEO ) MODEM/TNC • UO-22 • KO-23 SOFTWARE • KO-25 POWER SYSTEM BACKUP PLAN REASONS: TIMELINE • Make the system easier to implement OBSTICLES • Limited funding • Can avoid undesired signal distortions due to Doppler QUESTION Effect, Faraday Rotation Effect and Spin Modulation effect . CE3992
Gateway to Amateur Satellites for Internet Users Gateway to Amateur Satellites for Internet Users ANTENNA SYSTEM: Characteristics HISTORY SATELLITE SPECS 1. Directional Properties( gain and pattern ) ANTENNA SYSTEM ANTENNA SYSTEM PRE AMPLIFICATION PRE AMPLIFICATION 2. Transmission vs Reception properties ROTATOR CONTROLLER MODEM/TNC 3. Efficiency SOFTWARE POWER SYSTEM 4. Polarization BACKUP PLAN TIMELINE 5. Link effect (spin modulation, Faraday OBSTICLES rotation) QUESTION CE3992
Gateway to Amateur Satellites for Internet Users Gateway to Amateur Satellites for Internet Users ANTENNA SYSTEM: Direction properties HISTORY Idle antenna SATELLITE SPECS - An array that radiates power equally in all directions ANTENNA SYSTEM ANTENNA SYSTEM PRE AMPLIFICATION PRE AMPLIFICATION Expected antenna: Yagi ROTATOR CONTROLLER - A beam acts by MODEM/TNC concentrating its radiated SOFTWARE energy in a specific POWER SYSTEM direction. BACKUP PLAN TIMELINE Yagi has better gain than dipole. OBSTICLES QUESTION Yagi = 2 * dipole Yagi = 2 * dipole CE3992
Gateway to Amateur Satellites for Internet Users Gateway to Amateur Satellites for Internet Users ANTENNA SYSTEM: RX & TX properties HISTORY Basic Law: reciprocity principle SATELLITE SPECS - The gain pattern of an antenna is same for ANTENNA SYSTEM ANTENNA SYSTEM reception as for transmission. PRE AMPLIFICATION PRE AMPLIFICATION ROTATOR CONTROLLER Real World: signal & noise (S/N ) ratio MODEM/TNC - Though high efficiency and gain contribute to our goal, the shape of the gain pattern and the SOFTWARE location of null may have a significant impact on POWER SYSTEM S/N ratio by reducing noise and interfering BACKUP PLAN signals. TIMELINE OBSTICLES Thumb of Rule - A good antenna for transmitting to satellite is not QUESTION necessary a desirable antenna for receiving signals from a satellite. CE3992
Gateway to Amateur Satellites for Internet Users Gateway to Amateur Satellites for Internet Users ANTENNA SYSTEM: Efficiency HISTORY SATELLITE SPECS • A transmitting antenna that is 100% efficient ANTENNA SYSTEM ANTENNA SYSTEM radiates all the power reaching its input PRE AMPLIFICATION PRE AMPLIFICATION terminals. ROTATOR CONTROLLER MODEM/TNC • A transmitting antenna that is 50% efficient SOFTWARE only radiates half the power appearing at its POWER SYSTEM input terminals. BACKUP PLAN TIMELINE • Note : If efficiency is lower than 80%, Note OBSTICLES antenna needs to be disconnected to avoid QUESTION damage to Radio. CE3992
Gateway to Amateur Satellites for Internet Users Gateway to Amateur Satellites for Internet Users ANTENNA SYSTEM: Polarization HISTORY Radio waves consist of electric and magnetic SATELLITE SPECS fields, both of which are always present and ANTENNA SYSTEM ANTENNA SYSTEM inseparable. When a radio wave passes a PRE AMPLIFICATION PRE AMPLIFICATION point in space, the electric field at that point ROTATOR CONTROLLER varies cyclically at the frequency of the MODEM/TNC wave. When we discuss the ‘ polarization of a SOFTWARE radio wave’ we’re focusing on how the POWER SYSTEM electric field varies. BACKUP PLAN TIMELINE Most amateur antennas are designed to OBSTICLES respond primarily to the electric field. QUESTION CE3992
Gateway to Amateur Satellites for Internet Users Gateway to Amateur Satellites for Internet Users ANTENNA SYSTEM: How to build HISTORY SATELLITE SPECS Obstacles ANTENNA SYSTEM ANTENNA SYSTEM -Building an antenna that can match all these PRE AMPLIFICATION PRE AMPLIFICATION characteristics is a difficult task. ROTATOR CONTROLLER Fortunately, we are able MODEM/TNC to make use of already SOFTWARE developed software for POWER SYSTEM antenna design BACKUP PLAN TIMELINE Software will generate exact OBSTICLES measurements for each element of the antenna QUESTION CE3992
Gateway to Amateur Satellites for Internet Users Gateway to Amateur Satellites for Internet Users ANTENNA SYSTEM: Specification for ours HISTORY SATELLITE SPECS The length of two Antennas ANTENNA SYSTEM ANTENNA SYSTEM - 70 cm & 2 meters PRE AMPLIFICATION PRE AMPLIFICATION Height ROTATOR CONTROLLER - 2 meters MODEM/TNC SOFTWARE Power POWER SYSTEM - 12 V & Max 10A BACKUP PLAN TIMELINE Cost ( without rotator ) OBSTICLES - $60 QUESTION CE3992
Gateway to Amateur Satellites for Internet Users Gateway to Amateur Satellites for Internet Users PRE AMPLIFICATION • Amplifier signal from satellite HISTORY SATELLITE SPECS • One Pre-Amplifier circuit needed ANTENNA SYSTEM • Components PRE AMPLIFICATION PRE AMPLIFICATION ROTATOR CONTROLLER – (8) Capacitors MODEM/TNC – (3) Inductors SOFTWARE – (1) Diode POWER SYSTEM – (2) RCA Jack BACKUP PLAN – (1) MES FET TIMELINE – (4) Resistors OBSTICLES QUESTION Estimated cost $20 CE3992
Gateway to Amateur Satellites for Internet Users Gateway to Amateur Satellites for Internet Users ROTATOR CONTROLLER HISTORY • M68HC11 Motorola Microcontroller SATELLITE SPECS • Max232 chip for serial communication ANTENNA SYSTEM • Breadboard, wires, capacitors, resistors etc PRE AMPLIFICATION • D/A converter, connecters ROTATOR CONTROLLER ROTATOR CONTROLLER MODEM/TNC Microcontroller Computer Serial Interface SOFTWARE POWER SYSTEM BACKUP PLAN Estimated cost $25 TIMELINE Digital Analog converter OBSTICLES Driver Cir. Driver Cir. QUESTION X-Motor Y-Motor CE3992
Recommend
More recommend
