University of Twente Student Theses


Antenna system design for OLGAR"s inter-satellite link

Willink Castro, Teodoro J. (2012) Antenna system design for OLGAR"s inter-satellite link.

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Abstract:Initiatives to perform space-based radio astronomy below 30 MHz have emerged recently, since novel technological developments have increased their feasibility. The Orbiting Low-Frequency Antennas for Radio Astronomy (OLFAR) project, one of these initiatives, aims to use a swarm of nano-satellites to implement a radio interferometric array in space to observe celestial radiation with frequencies in the range of 0.3 MHz to 30 MHz. For its astronomical tasks, OLFAR requires that every satellite is able to establish a high-data-rate radio link with all the others. The inter-satellite communications subsystem of each satellite consists in a data distribution strategy, the coding, modulation and multiple access schemes and an antenna system, which is addressed in this work. The antenna system capacity requirements are influenced by the data rate generated by the astronomical observations, as well as the configuration of the data distribution strategy and the communication schemes. Moreover, the antenna system design must also consider the spatial configuration of the interferometric array, since it determines the possible link directions. Additionally, the physical dimensions of the nano-satellites impose important restrictions in available area for the intersatellite link (ISL) antennas and the transmission power. From all these, we identify the antenna system’s requirements and limitations: it must provide enough gain for any link direction given the available area constraint. To meet these, we present a proposal that consists of four aspects: an antenna configuration, a control scheme, the relevant antenna characteristics and the transceiver architecture possibilities. Six antennas, one on each face of the nano-satellite, make up the proposed antenna configuration. The proposed control scheme is a tailored beamforming algorithm that maxmimizes the antenna system gain for any link direction. The relevant individual antenna characteristics include bandwidth, radiation pattern, polarization, impedance and efficiency. Moreover, a discussion on antenna implementation alternatives for different ISL frequencies is also presented. Finally, digital baseband control is proposed to be used in the transceiver, despite of the additional hardware that it may require. v VI SUMMARY To validate this proposal, we developed an analytical model and an experimental evaluation platform, which we use to evaluate the performance of the proposed antenna system. The obtained results show that it is possible to obtain the required performance theoretically, although in practice it may not be totally achievable. We conclude that the proposal meets the identified requirements and limitations with an efficient solution, at the expense of high system complexity. However, the proposed design is flexible enough to consider simpler implementations if the requirements are loosened. We recommend that further work is carried out towards a careful design of the individual antennas and the integrated transceiver, since they can provide useful insight on their achievable performance and requirements.
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:53 electrotechnology
Programme:Electrical Engineering MSc (60353)
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