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International Journal of Antennas and Propagation
Volume 2013 (2013), Article ID 873234, 17 pages
http://dx.doi.org/10.1155/2013/873234
Research Article

Compact, Slotted, Printed Antennas for Dual-Band Communication in Future Wireless Sensor Networks

Mobile Radio Communications Laboratory, National Technical University of Athens, Zographos Polytechnic Campus, 9 Iroon Polytechniou Street, 15773 Athens, Greece

Received 13 August 2012; Revised 25 October 2012; Accepted 20 December 2012

Academic Editor: Fan Yang

Copyright © 2013 Constantine G. Kakoyiannis and Philip Constantinou. 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

Inverted-F antennas (IFAs) are a primary choice to implement the radiating system of portable devices. A tried and tested idea can remain topical if proven useful in modern applications. This paper shows that printed IFAs (PIFAs) are capable of forming robust, compact, dual-band radiating systems for wireless microsensors with an adjustable spacing between bands. Reactive tuning was applied by inductively loading the structures with prefractal slots; inductive slot loading degenerates higher-order resonances and increases the fractional bandwidth (FBW). The current distributions revealed that most of the element area is used for radiation at both resonances. In radiation terms, the antennas provide satisfactory gains and high efficiencies (≥82%). A simple figure of merit is used to compare the performance of the three PIFAs head to head. Operation at 2.5 GHz and 5.5 GHz indicated that changes in slot geometry almost double the FBW. The proposed antennas serve both the 5.15–5.35 GHz U-NII and the 5.8 GHz ISM bands; at the lower band, their size is less or equal to the half-wavelength dipole. This study of dual-band antennas also showed that the aggregate FBW of a PIFA is bounded; by degenerating higher-order modes, the designer redistributes whatever bandwidth is available by the antenna itself to the desired bands.