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Open AccessArticle

Potential of Sub-GHz Wireless for Future IoT Wearables and Design of Compact 915 MHz Antenna

1
Tyndall National Institute, University College Cork, Dyke Parade, T12R5CP Cork, Ireland
2
Sanmina Corporation, 13000 S. Memorial Parkway, Huntsville, AL 35803, USA
3
Sanmina Ireland, Rathealy Road, Fermoy, P61FX24 County Cork, Ireland
*
Author to whom correspondence should be addressed.
Sensors 2018, 18(1), 22; https://doi.org/10.3390/s18010022
Received: 6 September 2017 / Revised: 8 December 2017 / Accepted: 19 December 2017 / Published: 22 December 2017
(This article belongs to the Special Issue Next Generation Wireless Technologies for Internet of Things)
Internet of Things (IoT) technology is rapidly emerging in medical applications as it offers the possibility of lower-cost personalized healthcare monitoring. At the present time, the 2.45 GHz band is in widespread use for these applications but in this paper, the authors investigate the potential of the 915 MHz ISM band in implementing future, wearable IoT devices. The target sensor is a wrist-worn wireless heart rate and arterial oxygen saturation (SpO2) monitor with the goal of providing efficient wireless functionality and long battery lifetime using a commercial Sub-GHz low-power radio transceiver. A detailed analysis of current consumption for various wireless protocols is also presented and analyzed. A novel 915 MHz antenna design of compact size is reported that has good resilience to detuning by the human body. The antenna also incorporates a matching network to meet the challenging bandwidth requirements and is fabricated using standard, low-cost FR-4 material. Full-Wave EM simulations are presented for the antenna placed in both free-space and on-body cases. A prototype antenna is demonstrated and has dimensions of 44 mm × 28 mm × 1.6 mm. The measured results at 915 MHz show a 10 dB return loss bandwidth of 55 MHz, a peak realized gain of 2.37 dBi in free-space and 6.1 dBi on-body. The paper concludes by highlighting the potential benefits of 915 MHz operation for future IoT devices. View Full-Text
Keywords: IoT; ISM band; small antenna; wearable; medical; SpO2; wireless sensor; wrist-worn antenna IoT; ISM band; small antenna; wearable; medical; SpO2; wireless sensor; wrist-worn antenna
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Di Serio, A.; Buckley, J.; Barton, J.; Newberry, R.; Rodencal, M.; Dunlop, G.; O’Flynn, B. Potential of Sub-GHz Wireless for Future IoT Wearables and Design of Compact 915 MHz Antenna. Sensors 2018, 18, 22.

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