The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Compact UHF-Band Antennas for Mobile Terminals: Focus on Modelling, Implementation, and User Interaction

Jari Holopainen

Doctoral dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the School of Electrical Engineering for public examination and debate in Auditorium S4 at the Aalto University School of Electrical Engineering (Espoo, Finland) on the 29th of April 2011 at 12 noon.

Overview in PDF format (ISBN 978-952-60-4086-8)   [10799 KB]
Dissertation is also available in print (ISBN 978-952-60-4085-1)

Abstract

The background of this thesis is the trend of ever decreasing space available for antennas embedded within mobile terminals. At the same time the antennas are increasingly required to cover a large number of separate frequency bands and/or have wideband operation. In addition, those antennas should perform sufficiently well in the vicinity of the user. This forms the motivation for the novel compact coupling-based antennas introduced and studied in this thesis.

The operation of the compact coupling antennas is based on exploiting the separate wavemodes supported by the chassis of the mobile terminal. The antenna element itself functions mainly as a coupler which couples to those chassis wavemodes. That is the reason why they are called coupling-based antennas. This work concentrates on the modelling, implementation and design of such antennas in free space, and the effect of the user on the operation of the antenna. The understanding gained in this thesis can be exploited in the development of the antennas for mobile terminals of the future.

In the first part of the thesis, an equivalent circuit model is derived for a capacitive coupling-based antenna. This model gives a helpful physical explanation for the operation of this type of antennas. Broadband small antennas operating in the lower part of the UHF band are also implemented and analysed in detail. These kinds of antennas could find applications, for example, in digital television reception, low-band LTE, or the spectrum sensing of cognitive radios. Furthermore, it is shown that very low-profile antennas can be implemented by exciting the chassis wavemodes galvanically with a direct feed. The implementation of frequency-tuneable antennas is also studied in order to cover broad virtual bandwidth or several separate non-simultaneous frequency bands. The second part of this thesis discusses issues concerning user interaction with the coupling-based antennas. The antenna-user interaction is first modelled with an equivalent circuit which provides an improved understanding of the phenomenon. Then, the effects of the user's hands on the operation of the broadband lower UHF-band antenna is studied in detail. In the end of the thesis, a method for reshaping the near fields of the mobile terminal antenna is also proposed, for example, for improved hearing-aid compatibility.

This thesis consists of an overview and of the following 8 publications:

  1. Jari Holopainen, Risto Valkonen, Outi Kivekäs, Janne Ilvonen, and Pertti Vainikainen. 2010. Broadband equivalent circuit model for capacitive coupling element–based mobile terminal antenna. IEEE Antennas and Wireless Propagation Letters, volume 9, pages 716-719. © 2010 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  2. Jari Holopainen, Outi Kivekäs, Clemens Icheln, and Pertti Vainikainen. 2010. Internal broadband antennas for digital television receiver in mobile terminals. IEEE Transactions on Antennas and Propagation, volume 58, number 10, pages 3363-3374. © 2010 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  3. Risto Valkonen, Jari Holopainen, Clemens Icheln, and Pertti Vainikainen. 2008. Minimization of power loss and distortion in a tuning circuit for a mobile terminal antenna. In: Proceedings of the 13th International Symposium on Antennas and Propagation (ISAP 2008). Taipei, Taiwan. 27-30 October 2008. Tokyo, Japan. Institute of Electronics, Information and Communication Engineers. Pages 449-452. © 2008 Institute of Electronics, Information and Communication Engineers (IEICE). By permission.
  4. Jari Holopainen, Juha Villanen, Clemens Icheln, and Pertti Vainikainen. 2006. Mobile terminal antennas implemented by using direct coupling. In: Proceedings of the 1st European Conference on Antennas and Propagation (EuCAP 2006). Nice, France. 6-10 November 2006. SP-626, CD-ROM, paper OA17 349858jh.pdf. 6 pages. ISBN 92-9092-937-5. © 2006 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  5. J. Holopainen, J. Villanen, R. Valkonen, J. Poutanen, O. Kivekäs, C. Icheln, and P. Vainikainen. 2009. Mobile terminal antennas implemented using optimized direct feed. In: Proceedings of the 2009 IEEE International Workshop on Antenna Technology (iWAT 2009). Santa Monica, California, USA. 2-4 March 2009. IEEE. Paper PS202. 4 pages. ISBN 978-1-4244-4396-3. © 2009 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  6. J. Holopainen, R. Valkonen, O. Kivekäs, J. Ilvonen, L. Martínez, P. Vainikainen, J. R. Kelly, and P. S. Hall. 2010. Equivalent circuit model-based approach on the user body effect of a mobile terminal antenna. In: Proceedings of the 2010 Loughborough Antennas & Propagation Conference (LAPC 2010). Loughborough, UK. 8-9 November 2010. Loughborough University. Pages 217-220. ISBN 978-1-4244-7305-2. © 2010 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  7. Jari Holopainen, Outi Kivekäs, Janne Ilvonen, Risto Valkonen, Clemens Icheln, and Pertti Vainikainen. 2011. Effect of the user's hands on the operation of lower UHF-band mobile terminal antennas: Focus on digital television receiver. IEEE Transactions on Electromagnetic Compatibility, volume 53, to be published in a future issue, 11 pages. © 2011 Institute of Electrical and Electronics Engineers (IEEE). By permission.
  8. Jari Holopainen, Janne Ilvonen, Outi Kivekäs, Risto Valkonen, Clemens Icheln, and Pertti Vainikainen. 2009. Near-field control of handset antennas based on inverted-top wavetraps: Focus on hearing-aid compatibility. IEEE Antennas and Wireless Propagation Letters, volume 8, pages 592-595. © 2009 Institute of Electrical and Electronics Engineers (IEEE). By permission.

Keywords: capacitive coupling element, digital television, direct feed, equivalent circuits, hearing-aid compatibility, mobile antennas, receiving antennas, frequency-tuneable antennas, user effect

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Last update 2011-05-26