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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Studies on an Amplitude Hologram as the Collimator in a Submillimeter-Wave Compact Antenna Test Range

Tomi Koskinen

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Electrical and Communications Engineering for public examination and debate in Auditorium S1 at Helsinki University of Technology (Espoo, Finland) on the 20th of June, 2007, at 12 o'clock noon.

Overview in PDF format (ISBN 978-951-22-8796-3)   [854 KB]
Dissertation is also available in print (ISBN 978-951-22-8795-6)

Abstract

This thesis is based on the research work, the objective of which has been to develop a hologram-based compact antenna test range (CATR) for submillimeter wavelengths. Such a measurement facility is needed for testing antennas of, e.g., astronomical and Earth observation satellites. The further objective has been to improve electrical characteristics of the hologram, as well as its manufacturing properties. The hologram studied in this thesis is a slot pattern processed on a thin metal-plated Mylar film and it is used as a transmission-type collimating element.

A hologram-based CATR was designed and constructed for 322 GHz and was used for testing a 1.5 meter reflector antenna (Admirals RTO). A hologram of 3 meters in diameter was soldered together from three pieces, which were manufactured on 50 µm-thick copper-plated Mylar film by using laser-exposure and wet-etching. Partly due to manufacturing errors, the measured quiet-zone amplitude and phase deviations were appr. 1.2 dB and 250° within a region of 1.5 meters in diameter. The effect of these deviations on antenna measurement results was estimated by simulations.

Feasibility of the hologram for 650 GHz has also been studied. Laser-exposure and wet-etching has been found to be a potentially suitable manufacturing method for frequencies up to 1000 GHz. The 50 µm Mylar film is a suitable material for frequencies up to 650 GHz, but at higher frequencies the film has to be thinner to avoid resonances inside the film. The 25 µm Mylar film is estimated to be suitable for frequencies up to 1000 GHz.

According to studies at 310 GHz, the hologram works well also as a reflection-type element. In the reflection-type setup, the power loss of the hologram is appr. 7.4 dB that is 4 dB lower than that in the transmission-type setup.

Using a shaped beam for illumination has been studied at 310 GHz. A hologram pattern designed for such an illumination can be simplified from one designed for a conventional horn illumination. A simplified hologram pattern is easier to manufacture and it is more robust against manufacturing errors. In addition, its polarization properties are significantly improved: operation at the horizontal polarization is possible and cross-polarization is reduced substantially. Earlier, the operation of the hologram has been possible only at the vertical polarization. According to these studies, it appears that by using a shaped illumination the operation can be designed to be almost independent of polarization.

This thesis consists of an overview and of the following 9 publications:

  1. A. Lönnqvist, T. Koskinen, J. Häkli, J. Säily, J. Ala-Laurinaho, J. Mallat, V. Viikari, J. Tuovinen, and A. V. Räisänen, Hologram-based compact range for submillimeter-wave antenna testing, IEEE Transactions on Antennas and Propagation, vol. 53, no. 10, pp. 3151-3159, Oct. 2005. © 2005 IEEE. By permission.
  2. J. Häkli, T. Koskinen, A. Lönnqvist, J. Säily, V. Viikari, J. Mallat, J. Ala-Laurinaho, J. Tuovinen, and A. V. Räisänen, Testing of a 1.5-m reflector antenna at 322 GHz in a CATR based on a hologram, IEEE Transactions on Antennas and Propagation, vol. 53, no. 10, pp. 3142-3150, Oct. 2005. © 2005 IEEE. By permission.
  3. J. Salo, J. Meltaus, E. Noponen, M. M. Salomaa, A. Lönnqvist, T. Koskinen, V. Viikari, J. Säily, J. Häkli, J. Ala-Laurinaho, J. Mallat, and A. V. Räisänen, Holograms for shaping radio-wave fields, Journal of Optics A: Pure and Applied Optics, vol. 4, no. 5, pp. S161-S167, Sep. 2002. © 2002 Institute of Physics Publishing. By permission.
  4. T. Koskinen, V. Viikari, J. Häkli, A. Lönnqvist, J. Ala-Laurinaho, J. Mallat, and A. V. Räisänen, A reflection-type amplitude hologram as a collimating element in the compact antenna test range, in Proceedings of the 27th Annual Meeting and Symposium of the Antenna Measurement Techniques Association (AMTA 2005), Newport, RI, USA, Oct. 30 - Nov. 4, 2005, pp. 417-421. © 2005 by authors.
  5. T. Koskinen, J. Mallat, A. Lönnqvist, J. Säily, J. Häkli, J. Ala-Laurinaho, J. Tuovinen, and A. V. Räisänen, Performance of a small 650 GHz hologram, in Digest of the 2003 IEEE International Antennas and Propagation Symposium, Columbus, OH, USA, June 22-27, 2003, vol. 3, pp. 532-535. © 2003 IEEE. By permission.
  6. T. Koskinen, J. Ala-Laurinaho, J. Säily, A. Lönnqvist, J. Häkli, J. Mallat, J. Tuovinen, and A. V. Räisänen, Experimental study on a hologram-based compact antenna test range at 650 GHz, IEEE Transactions on Microwave Theory and Techniques, vol. 53, no. 9, pp. 2999-3006, Sep. 2005. © 2005 IEEE. By permission.
  7. J. Häkli, T. Koskinen, J. Ala-Laurinaho, and A. V. Räisänen, Dual reflector feed system for hologram-based compact antenna test range, IEEE Transactions on Antennas and Propagation, vol. 53, no. 12, pp. 3940-3948, Dec. 2005. © 2005 IEEE. By permission.
  8. T. Koskinen, J. Häkli, J. Ala-Laurinaho, A. Lönnqvist, V. Viikari, J. Mallat, and A. V. Räisänen, Study on the dual polarized operation of the hologram based compact antenna test range, in Proceedings of the 28th ESA Antenna Workshop on Space Antenna Systems and Technologies, ESTEC, Noordwijk, The Netherlands, May 31 - June 3, 2005, pp. 401-406.
  9. T. Koskinen, J. Ala-Laurinaho, J. Häkli, and A. V. Räisänen, Studies on an amplitude hologram as a submillimeter-wave collimator at circular polarisation, in Proceedings of the 1st European Conference on Antennas and Propagation (EuCAP 2006), Nice, France, Nov. 6-10, 2006, CD-ROM, ISBN 92-9092-937. © 2006 IEEE. By permission.

Keywords: hologram, compact antenna test range, CATR, submillimeter waves

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© 2007 Helsinki University of Technology

Last update 2011-05-26