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.
Aalto

Microwave Transmission-Line Networks for Backward-Wave Media and Reduction of Scattering

Pekka Alitalo

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Faculty of Electronics, Communications and Automation for public examination and debate in Auditorium S4 at Helsinki University of Technology (Espoo, Finland) on the 7th of August, 2009, at 12 noon.

Overview in PDF format (ISBN 978-951-22-9987-4)   [1419 KB]
Dissertation is also available in print (ISBN 978-951-22-9986-7)

Abstract

This thesis investigates the use of transmission-line networks in various structures and devices that exhibit exotic response to impinging electromagnetic radiation. The main topics that are studied are media supporting backward-wave propagation, structures capable of electromagnetic cloaking, and a novel way of implementing microwave lenses with volumetric transmission-line networks.

Backward-wave media support propagation of electromagnetic waves for which the phase advances in the direction opposite to the energy propagation. Such media can be very useful due to certain exotic phenomena, for example, negative refraction and resonant enhancement of evanescent fields, that enable imaging with sub-wavelength resolution. In this thesis, the analysis methods derived for two-dimensional backward-wave transmission-line networks are developed for the generalized three-dimensional case, and the results are verified with numerical simulations and measurements. A way of coupling electromagnetic fields between a transmission-line network and a homogeneous medium surrounding such a network is proposed and the operation of this coupling method is verified with numerical simulations.

The idea of tailoring material properties to obtain electromagnetic cloaking of scattering objects has been extensively studied in the recent literature. This phenomenon can be achieved with various methods. In this thesis a cloaking method based on volumetric structures composed of transmission-line networks is proposed and studied. The basic principle of cloaking and the related restrictions are analytically explained and the cloaking phenomenon is verified with numerical simulations and measurements.

Coupling of electromagnetic fields between a transmission-line network and a homogeneous medium surrounding such a network enables the utilization of these artificial materials in, for example, antenna applications. In this thesis this possibility is used in implementing microwave lenses that can mitigate the unwanted reflections that are inherent to any conventional dielectric lens.

This thesis consists of an overview and of the following 12 publications:

  1. Pekka Alitalo, Stanislav Maslovski, and Sergei Tretyakov. 2006. Three-dimensional isotropic perfect lens based on LC-loaded transmission lines. Journal of Applied Physics, volume 99, number 6, 064912. © 2006 American Institute of Physics. By permission.
  2. Pekka Alitalo, Stanislav Maslovski, and Sergei Tretyakov. 2006. Experimental verification of the key properties of a three-dimensional isotropic transmission-line superlens. Journal of Applied Physics, volume 99, number 12, 124910. © 2006 American Institute of Physics. By permission.
  3. Pekka Alitalo and Sergei Tretyakov. 2007. Subwavelength resolution with three-dimensional isotropic transmission-line lenses. Metamaterials, volume 1, number 2, pages 81-88. © 2007 Elsevier Science. By permission.
  4. Pekka Alitalo, Olli Luukkonen, and Sergei Tretyakov. 2008. A three-dimensional backward-wave network matched with free space. Physics Letters A, volume 372, number 15, pages 2720-2723. © 2007 Elsevier Science. By permission.
  5. Pekka Alitalo, Frédéric Bongard, Juan Mosig, and Sergei Tretyakov. 2009. Backward-wave slab with electrically tunable index of refraction. In: Proceedings of the 3rd European Conference on Antennas and Propagation (EuCAP 2009). Berlin, Germany. 23-27 March 2009, pages 1667-1671. © 2009 IEEE. By permission.
  6. Pekka Alitalo, Olli Luukkonen, Liisi Jylhä, Jukka Venermo, and Sergei A. Tretyakov. 2008. Transmission-line networks cloaking objects from electromagnetic fields. IEEE Transactions on Antennas and Propagation, volume 56, number 2, pages 416-424. © 2008 IEEE. By permission.
  7. Pekka Alitalo, Sylvain Ranvier, Joni Vehmas, and Sergei Tretyakov. 2008. A microwave transmission-line network guiding electromagnetic fields through a dense array of metallic objects. Metamaterials, volume 2, number 4, pages 206-212. © 2008 Elsevier Science. By permission.
  8. Pekka Alitalo, Frédéric Bongard, Jean-Francois Zürcher, Juan Mosig, and Sergei Tretyakov. 2009. Experimental verification of broadband cloaking using a volumetric cloak composed of periodically stacked cylindrical transmission-line networks. Applied Physics Letters, volume 94, number 1, 014103. © 2009 American Institute of Physics. By permission.
  9. Pekka Alitalo, Olli Luukkonen, Frédéric Bongard, Jean-Francois Zürcher, Juan R. Mosig, and Sergei A. Tretyakov. 2009. Broadband cloaking of selected objects in the microwave regime with a volumetric cloak comprising layered networks of transmission lines. In: Proceedings of the 2009 IEEE International Symposium on Antennas and Propagation. Charleston, South Carolina, USA. 1-5 June 2009, p. 222.2. © 2009 IEEE. By permission.
  10. Pekka Alitalo, Olli Luukkonen, Juan R. Mosig, and Sergei A. Tretyakov. 2009. Broadband cloaking with volumetric structures composed of two-dimensional transmission-line networks. Microwave and Optical Technology Letters, volume 51, number 7, pages 1627-1631.
  11. Pekka Alitalo, Olli Luukkonen, Joni Vehmas, and Sergei A. Tretyakov. 2008. Impedance-matched microwave lens. IEEE Antennas and Wireless Propagation Letters, volume 7, pages 187-191. © 2008 IEEE. By permission.
  12. Pekka Alitalo, Frédéric Bongard, Juan Mosig, and Sergei Tretyakov. 2009. Transmission-line lens antenna with embedded source. In: Proceedings of the 3rd European Conference on Antennas and Propagation (EuCAP 2009). Berlin, Germany. 23-27 March 2009, pages 625-629. © 2009 IEEE. By permission.

Keywords: transmission line, backward wave, electromagnetic cloaking, scattering cross section

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© 2009 Helsinki University of Technology

Last update 2011-05-26