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International Journal of Antennas and Propagation
Volume 2013, Article ID 684185, 6 pages
http://dx.doi.org/10.1155/2013/684185
Research Article

A Twin Spiral Planar Antenna for UWB Medical Radars

1Gerontechnology and Rehabilitation Group, ARTORG Center for Biomedical Engineering Research, University of Bern, 3010 Bern, Switzerland
2Haute École d'Ingénierie et de Gestion du Canton de Vaud, Western Switzerland University of Applied Sciences (HES-SO), 1401 Yverdon-les-Bains, Switzerland
3Department of Information Engineering, Electronics and Telecommunications, Sapienza University of Rome, 00184 Rome, Italy

Received 1 October 2012; Accepted 19 November 2012

Academic Editor: Renato Cicchetti

Copyright © 2013 Giuseppe A. Zito et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

A planar-spiral antenna to be used in an ultrawideband (UWB) radar system for heart activity monitoring is presented. The antenna, named “twin,” is constituted by two spiral dipoles in a compact structure. The reflection coefficient at the feed point of the dipoles is lower than −8 dB over the 3–12 GHz band, while the two-dipoles coupling is about −20 dB. The radiated beam is perpendicular to the plane of the spiral, so the antenna is wearable and it may be an optimal radiator for a medical UWB radar for heart rate detection. The designed antenna has been also used to check some hypotheses about the UWB radar heart activity detection mechanism. The radiation impedance variation, caused by the thorax vibrations associated with heart activity, seems to be the most likely explanation of the UWB radar operation.