Design of a compact, fully-autonomous 433 MHz tunable antenna for wearable wireless sensor applications
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Accepted Version
Date
2017-03-18
Authors
Buckley, John
McCarthy, Kevin G.
Gaetano, Domenico
Loizou, Loizos
O'Flynn, Brendan
Ó Mathúna, S. Cian
Journal Title
Journal ISSN
Volume Title
Publisher
Institution of Engineering and Technology (IET)
Published Version
Abstract
The authors present the design of a tunable 433 MHz antenna that is tailored for wearable wireless sensor applications. This study first presents a detailed analysis of the measured impedance characteristics of a chosen antenna under test (AUT) in varying proximity to a human test subject. Instead of limiting the analysis to the head and hand only, this analysis measures the AUT impedance at varying distances from 11 different body positions. A novel antenna equivalent circuit model is then developed that enables both the free-space and total on-body AUT impedance variation to be rapidly computed using a circuit simulator instead of the requirement for computationally intensive finite-element methods for example. The design and characterisation of a tunable matching network that enables AUT impedance matching for 11 different positions on the human body is then outlined. Finally, a fully-autonomous 433 MHz tunable antenna is demonstrated. The antenna occupies a small printed circuit board area of 51 × 28 mm and is printed on standard FR-4 material with the tuner completely integrated into the antenna itself. Prototype measurements show an improvement of 3.9 dB in power delivery to the antenna for a load voltage standing wave ratio of 17:1, with a maximum matching loss of 0.84 dB and S 11 (−10 dB) ≥ 18 MHz for all load conditions.
Description
Keywords
Impedance matching , Body sensor networks , Wearable antennas , Microstrip antennas , UHF antennas , Printed circuits , Antenna testing , Equivalent circuits
Citation
Buckley, J. L., McCarthy, K. G., Gaetano, D., Loizou, L., O'Flynn, B. and O'Mathuna, C. (2017) 'Design of a compact, fully-autonomous 433 MHz tunable antenna for wearable wireless sensor applications', IET Microwaves, Antennas and Propagation, 11(4), pp. 548-556. doi: 10.1049/iet-map.2015.0712
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Copyright
© 2017, Institution of Engineering and Technology. This paper is a postprint of a paper submitted to and accepted for publication in IET Microwaves, Antennas and Propagation and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at the IET Digital Library.