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Karilainen A.O.,Aalto University | Ikonen P.M.T.,TDK EPC | Simovski C.R.,Aalto University | Tretyakov S.A.,Aalto University
IEEE Transactions on Antennas and Propagation | Year: 2011

We address the question of the optimal choice of loading material for antenna miniaturization. A new approach to identify the optimal loading material (dielectric or magnetic) for maximization of bandwidth of resonant antennas is introduced. Instead of equivalent resonant circuits or transmission-line resonators, we use the analysis of radiation mechanism to identify the fields contributing mostly to the stored energy and determine the beneficial material type. The formulated rule is qualitatively illustrated using a dipole and a patch antenna, as well as a planar inverted-L antenna where the conventional analysis of circuit or a transmission-line resonator leads to incorrect conclusions. Guidelines are presented for miniaturizing different antenna types. © 2011 IEEE.

Karilainen A.O.,Aalto University | Ikonen P.M.T.,TDK EPC | Simovski C.R.,Aalto University | Tretyakov S.A.,Aalto University | And 4 more authors.
IET Microwaves, Antennas and Propagation | Year: 2011

Dielectric or magneto-dielectric materials can be used to miniaturise antennas, but there are many important parameters that must be considered when selecting which material to use. The authors discuss these figures of merit and a rigorous method to compare antennas with different material fillings. A meandered planar inverted-F antenna (PIFA) loaded with magneto-dielectric and dielectric materials is presented as an example antenna for testing. The magneto-dielectric material used is composed of mylar substrate and Fe-SiO 2 sheets. Measurement results for the permeability of the material are presented. The radiation mechanism of the meandered PIFA is studied, and the proper position for dielectric and magneto-dielectric filling is discussed and identified. Miniaturisation by commercial dielectric and the presented magneto-dielectric fillings is measured and compared at the same resonance frequency using the radiation quality factor as the figure of merit. It is seen, that the antenna can benefit from the magneto-dielectric filling material in terms of the radiation quality factor only if the placement of the antenna filling is carefully selected. © 2011 The Institution of Engineering and Technology.

Bermejo R.,University of Leoben | Supancic P.,University of Leoben | Supancic P.,Materials Center Leoben Forschung | Aldrian F.,TDK EPC | And 2 more authors.
Scripta Materialia | Year: 2012

An experimental approach is proposed, based on localized biaxial testing of brittle samples at several locations under different environments, to quantify the effect of surface features or metallization (e.g. contacting pads or cylindrical vias) on the strength distribution of functional ceramic components. It is found that cylindrical vias can act as weak points in the design (i.e. lower strength and reliability), whereas contacting pads can raise the strength of the component acting as a protective layer against environmental degradation. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Savelsberg R.,Netherlands Defence Academy | Schiffer M.,TDK EPC | Obermeier E.,TU Berlin | Castro I.P.,University of Southampton
Experiments in Fluids | Year: 2012

Microelectromechanical systems (MEMS) sensors are increasingly used for measurements in fluid dynamics since, because of their inherently compact size, they allow access to the information that was previously unavailable. In this paper we describe further testing of a MEMS sensor used to measure surface shear stress. It is awall-mounted fence that bends under the influence of the pressure difference resulting from the velocity shear at the wall. The fences have been successfully calibrated in a wind tunnel and, as an example of their application, used to determine mean and fluctuating shear stress (along with spectra) in a cylindrical cavity flow. © Springer-Verlag 2012.

Lai J.C.Y.,Nanyang Technological University | Xu Y.,TDK EPC | Gunawan E.,Nanyang Technological University | Chua E.C.-P.,National University of Singapore | And 5 more authors.
IEEE Transactions on Instrumentation and Measurement | Year: 2011

The simultaneous tracking of the chest respiratory rate and amplitude of human beings using a low-power ultrawideband (UWB) impulse radio signal is investigated for the application of sleep apnea monitoring. The measurement of respiratory amplitude, in addition to the breathing rate, is crucial for sleep apnea assessment which requires, among other things, the accurate estimation of tidal volume per minute. Backscattered UWB impulse radio signals from a human subject are detected in the time domain to calculate the chest displacements in this paper. Since the pulse disposition in time is linearly related to the chest movement, the amplitude of the chest movement can be extracted accurately without calculation approximations normally used in many of the existing methods. The multipeak detection of the pulse disposition method, instead of using only the single pulse peak detection, is also proposed to improve the accuracy of the calculation further. The experiments are carried out on four human subjects with different sizes and genders. The correlation of the chest movements' amplitude and breathing rate between the simultaneously measured results obtained by our method and by the respiratory chest band is very good. © 2006 IEEE.

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