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Telecommunication satellite operators are increasingly encountering difficulties in managing the limited frequency spectrum allocated to TC and TM functions, while maintaining or improving the compatibility between communication channels and TCR and compatibility between satellites, especially in the case of collocated satellite fleets.
The use of spread spectrum for Telecommand and Ranging for commercial communication geostationary satellites is seen as a promising solution and has been initiated by the definition of ETSI standard EN 301 926 for spread spectrum TT&R.
The objective of this Project was to design, develop and manufacture a bread board model in order to verify the performances of a TT&C Transponder implementing the ETSI standard EN 301 926.
Thales Alenia Space, in the frame of the ARTES 5.1 SCOUT project, has developed a TT&R transponder compliant with this new standard. The objective of this activity was to design, develop and test a TT&R transponder bread board model compliant with the ETSI standard.
The Spread Spectrum and hybrid ranging functions have been developed and implemented in separate FPGAs for receiver and transmitter. They have been integrated and tested on development boards connected to the existing Ku band receiver RF front end and existing transmitter RF sections.
The study has demonstrated a strong improvement of the resistance to in-band interferers. Tests have shown compliance to ETSI standard assuming scenarios with up to 10 interferers. Telecom satellite operators will be able to manage more efficiently the limited frequency spectrum allocated to TC and TM functions, especially in the case of collocated satellite fleets.
A foreseen TT&R transponder configuration is shown in the next Figure.
The bi mode receiver is able to demodulate in parallel both FM or Spread Spectrum modulated uplink signal.
Block diagram of the forseenTAS dual mode Receiver:
For the SCOUT demonstrator, the spread spectrum demodulator is implemented in a FPGA. FPGA block diagram is shows here below:
The bi mode transmitter is able to modulate a in parallel both PM or Spread Spectrum modulated downlink signal.
The main characteristics of the transmitter are recalled in following table:
The project was composed of two phases. Phase 1 was dedicated to the feasibility analysis and pre-development of the spread spectrum feature algorithm.
The phase 1 was closed after a successful PDR. The phase 2 was dedicated of the validation of the ETSI standard through the development of the receiver and transmitter breadboard. A CDR closed the design phase followed by test campaign to validated the performance.
The Final review was held in July 2012.
The activity has been concluded and the Final Review was held in July 2012. The receiver and transmitter demonstrators are available at TAS premises. It is noted that an end-to-end test with a ground station modem is expected at the end of 2013, once the modem has been developed (in an ongoing ARTES contract).