Antenna Systems for NUTS
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
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.
ntnudaim:8238, MTEL elektronikk, Romteknologi og navigasjon
IdentifiersURN: urn:nbn:no:ntnu:diva-19424Local ID: ntnudaim:8238OAI: oai:DiVA.org:ntnu-19424DiVA: diva2:567045
Eide, Egil, Førsteamanuensis IIJensen, IreneBirkeland, Roger