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Antenna Systems for NUTS
Norwegian University of Science and Technology, Faculty of Information Technology, Mathematics and Electrical Engineering, Department of Electronics and Telecommunications.
2012 (English)MasteroppgaveStudent thesis
Abstract [en]

NTNU is aiming to build and launch a small student satellite compliant with the double CubeSat standard, by 2014. The NTNU Test Satellite (NUTS) will carry two radio tranceivers and a beacon transmitter, all located in the VHF and UHF amateur bands. The goal of this thesis was to build the whole antenna systems for the spacecraft. Turnstile antennas were chosen both for UHF and VHF, since they yield the highest received signal strength on ground throughout the whole pass of the satel- lite. In order to reach this conclusion, a study of how the choice of spacecraft antennas dynamically influence the link margin was carried out. Furthermore, the antennas was made by measuring tape, and is to be wrapped around the satellite until deployment. This is for the satellite to be within the size constraints of a double CubeSat during launch. The measuring tape will be tightened to the satel- lites body by nylon thread, which will be burnt off by Nichrome-wire to release the measuring tape when the satellite is in-orbit. The measuring tape is mounted in between two circuit boards constituting the internal part of the antenna module. The feeding network is encapsulated by these two circuit boards. The module is made such that the antenna complies with the CubeSat standard, and such that it can be integrated with other modules on-board the satellite, such as the camera. Feeding the antennas turned out more difficult than first anticipated. Whereas conventional feeding networks for turnstile antennas typically comprises baluns and arrangements of coaxial cable comparable to the wavelength, such solutions are not feasible within the satellite due to size constraints. As a result a lumped feeding network was designed, that could be mounted on one of the circuit boards. Because of the many reactive components in the feeding network, it became necessary to determine how deviations in component values affect the performance of the circuit. Statistical simulations was performed, and the deviations may cause an unbalance between the amplitudes and phases of the outputs. But this results in less than half a dB additional losses in the link budget. A refinement of electromagnetic antenna simulations from previous work was also carried out. With this, the performance of the antennas was verified, and their lengths were optimized to yield the best possible match. The VHF antenna is near-ideal both in terms of pattern and matching. The pattern of the UHF antenna is somewhat distorted, but it is still considered to be the best suited antenna of those considered. The matching of the UHF antenna could have been better, but is considered acceptable. Moreover, the mutual coupling between the VHF and UHF antennas were studied, with the conclusion that the antennas may very well co-exist on-board the satellite. Finally, both the feeding network and the VHF antenna were successfully built and tested. The feeding network had an insertion loss of less than 2 dB, whereas the pattern of the antenna was measured to be near-ideal. Unfortunately, a fault has occurred on the UHF feeding network, which also prohibits the pattern for the UHF antenna to be measured. Nonetheless, all the parts constituting it has been built, and all the necessary simulations are done. Previous and future troubleshooting of the feeding network is also discussed.

Place, publisher, year, edition, pages
Institutt for elektronikk og telekommunikasjon , 2012. , 268 p.
Keyword [no]
ntnudaim:8238, MTEL elektronikk, Romteknologi og navigasjon
URN: urn:nbn:no:ntnu:diva-19424Local ID: ntnudaim:8238OAI: diva2:567045
Available from: 2012-11-11 Created: 2012-11-11

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