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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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 S4 at Helsinki University of Technology (Espoo, Finland) on the 27th of April, 2007, at 12 o'clock noon.
Overview in PDF format (ISBN 978-951-22-8714-7) [1642 KB]
Dissertation is also available in print (ISBN 978-951-22-8713-0)
Hologram- and reflector-based compact antenna test ranges (CATRs) have shown potential for measurement of large submillimeter wave antennas. However, the measurement accuracy of these ranges needs to be still improved for measuring low side lobe antennas. The measurement accuracy of these ranges can be improved by using antenna pattern correction techniques. Several such techniques have been developed for microwave frequencies but most of them are not directly applicable at submillimeter wavelengths. In this thesis, four antenna pattern correction techniques that are applicable at submillimeter wavelengths are developed: feed scanning based antenna pattern comparison (APC) method, frequency shift method, and two methods that are based on a virtual antenna array. Applicabilities of these methods are studied analytically, and they are verified with simulations and measurements in a hologram-based compact antenna test range at 310 GHz.
The feed scanning based APC is applicable for compact antenna test ranges. In this method, the corrected antenna pattern is obtained from the antenna patterns measured with different range feed locations. The antenna pattern of the antenna under test (AUT) is measured at several frequencies in the frequency shift method. This method, which was originally developed for lower frequencies, is now found to be especially applicable for hologram-based CATRs. The method is able to compensate partially a possible non-ideal operation of the hologram, because a hologram is a dispersive element. Virtual array correction techniques are suitable for far-field and compact ranges. In these methods, the antenna pattern of the AUT is measured at several accurately known locations. These measurements form a virtual antenna array at each rotation angle of the AUT. The array factor of each array is modulated such that it has a constant gain towards the desired signal and high attenuation to other directions. Estimates of the antenna pattern of the antenna under test and the angular interference spectrum of the test range are taken into account in the array synthesis. One method uses an alternating projections method for array synthesis, whereas the other method maximizes the signal-to-interference ratio in the measurement. The correction accuracies of the feed scanning APC and frequency shift method are found to be approximately equal to that of the conventional APC. The correction accuracies of the virtual array methods are found to be much better than that of the APC.
This thesis consists of an overview and of the following 6 publications:
Keywords: antenna measurements, compact range, error compensation, submillimeter wave measurements
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© 2007 Helsinki University of Technology