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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Numerical Studies on a Radio Frequency Hologram and its Use in Antenna Measurements

Juha Ala-Laurinaho

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission for public examination and debate in Auditorium S1 at Helsinki University of Technology (Espoo, Finland) on the 25th of May 2001 at 12 o'clock noon.

Overview in PDF format (ISBN 951-22-5470-0)   [236 KB]
Dissertation is also available in print (ISBN 951-22-5446-8)

Abstract

This thesis deals with the compact antenna test range (CATR) based on a radio frequency hologram. The emphasis is on the development of the numerical analysis of the hologram. Several holograms have been fabricated and tested assessing the quality of the numerical analysis methods described in this thesis.

A CATR is a potential method for testing the electrically large antennas operating at millimetre and submillimetre wavelengths. These high-gain antennas are needed for remote sensing and radio-astronomical applications. A parabolic reflector is most often used as the collimating element in the CATR. However, at frequencies above 100 GHz, the reflector surface accuracy requirement becomes very stringent. To overcome this problem, it is proposed to use a binary amplitude hologram in the CATR. The hologram is a planar, transmission type of structure and the hologram pattern is realised on the metal plated dielectric film.

Typical requirements for the quiet-zone field quality are maximum amplitude and phase ripples of ±0.5 dB and ±5°, respectively. To achieve these requirements in the iterative hologram design procedure, an accurate method for evaluating the electromagnetic wave transmission through the hologram is needed. In this thesis, the finite difference time domain (FDTD) method is used for calculating the transmission of the hologram. However, the hologram structure is so large (at least several hundreds of wavelengths) that the whole hologram structure cannot be simulated at one time.

Two approaches are used for the simplification of the hologram structure: either 1) only one cut of the hologram is analysed at a time or 2) transmissions of electromagnetic wave through slots of different widths are studied and applied to the whole hologram analysis. The first method is used for optimising the holograms as it gives more accurate results. In addition, it is used when the bandwidth, tolerances, polarisation dependence, and planarity requirements of the hologram CATR are studied. The second method provides a tool for predicting cross-polarisation performance of the hologram CATR.

Experiments have been made at several frequencies: 39, 119, and 310 GHz. The results of these experiments show that the method of analysis developed in this thesis is adequate for designing the holograms. In addition, the feasibility of the hologram CATR operation for antenna measurements is demonstrated.

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

  1. T. Hirvonen, J. Ala-Laurinaho, J. Tuovinen, A. V. Räisänen: A compact antenna test range based on a hologram, IEEE Transactions on Antennas and Propagation, Vol. 45, No. 8, 1997, pp. 1270-1276. © 1997 IEEE. By permission.
  2. J. Ala-Laurinaho, T. Hirvonen, J. Tuovinen, A. V. Räisänen: Numerical modeling of a non-uniform grating with FDTD, Microwave and Optical Technology Letters, Vol. 15, No. 3, 1997, pp. 134-139.
  3. T. Hirvonen, J. Ala-Laurinaho, A. V. Räisänen: Performance analysis of a submillimeter wave hologram CATR, Proceedings of the 27th European Microwave Conference, Jerusalem, Israel, September 8-12, 1997, pp. 681-686. © 1997 IEEE. By permission.
  4. J. Ala-Laurinaho, T. Hirvonen, A. V. Räisänen: On the planarity errors of the hologram of the CATR, Proceedings of the IEEE Antennas and Propagation International Symposium, Orlando, Florida, USA, July 11-16, 1999, pp. 2166-2169. © 1999 IEEE. By permission.
  5. J. Ala-Laurinaho, T. Sehm, J. Säily, A. V. Räisänen: Cross-polarization performance of the hologram CATR, Microwave and Optical Technology Letters, Vol. 27, No. 4, 2000, pp. 225-229.
  6. J. Ala-Laurinaho, T. Hirvonen, A. V. Räisänen: A 40 GHz CATR based on a hologram, Proceedings of the 2nd ESA Workshop on Millimetre Wave Technology and Applications: Antennas, Circuits, and Systems, Espoo, Finland, May 27-29, 1998, pp. 542-547. © 1998 ESA. By permission.
  7. T. Sehm, J. Ala-Laurinaho, T. Hirvonen, A. V. Räisänen: Antenna measurements using a hologram CATR, Electronics Letters, Vol. 35, No. 10, 1999, pp. 757-758. © 1999 IEE. By permission.
  8. J. Ala-Laurinaho, T. Hirvonen, P. Piironen, A. Lehto, J. Tuovinen, A. V. Räisänen, U. Frisk: Measurement of the Odin telescope at 119 GHz with a hologram type CATR, to be published in IEEE Transactions on Antennas and Propagation, November 2001. © 2001 IEEE. By permission.
  9. J. Säily, J. Ala-Laurinaho, J. Häkli, J. Tuovinen, A. Lehto, A. V. Räisänen: Test results of a 310 GHz Hologram compact antenna test range, Electronics Letters, Vol. 36, No. 2, 2000, pp. 111-112. © 2000 IEE. By permission.

Keywords: antenna measurements, FDTD, compact antenna test ranges

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© 2001 Helsinki University of Technology

Last update 2011-05-26