Wearable Metasurface-Enabled Quasi-Yagi Antenna for UHF RFID Reader with End-Fire Radiation along the Forearm

Shahbaz Ahmed, Duc Le, Lauri Sydänheimo, Leena Ukkonen, Toni Björninen

    Research output: Contribution to journalArticleScientificpeer-review

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    We present a quasi-Yagi antenna mounted on a periodic surface for a wearable UHF RFID reader operating in the UHF RFID frequency band centered at 915 MHz. The periodic surface was co-optimized with the antenna to enhance the launching of surface waves to enable the end-fire radiation along the forearm so that a user can identify objects by pointing her/his hand towards them. In addition to the radiation pattern modification, the ground plane of the periodic surface serves the second purpose of isolating the antenna from the human body. We optimized the antenna in a full-wave EM simulator using a simplified cylindrical model of the forearm and in the simulation, it achieved the end-fire directivity of 5.9 dBi along the forearm. In the wireless testing, the quasi-Yagi antenna provided the read range of 3.8 m for a typical UHF RFID tag having 0 dBi gain when the reader’s output power was 32 dBm that corresponds with EIRP = 0.56 W and SAR = 0.191 W/kg in our simulations. Considering both, the RFID emission regulations with EIRP = 3.28 W or 4 W and the SAR limit of 1.6 W/kg averaged over 1 gram of tissue, the read range could be further enhanced for reader units with higher output power.

    Original languageEnglish
    Pages (from-to)77229 - 77238
    JournalIEEE Access
    Publication statusPublished - 2021
    Publication typeA1 Journal article-refereed


    • Antenna radiation patterns
    • Antennas
    • Directive antennas
    • periodic surface
    • Reflection
    • Surface impedance
    • surface wave antenna
    • Surface waves
    • UHF antennas
    • UHF RFID
    • Wearable antenna
    • wireless body-area systems
    • Yagi antenna

    Publication forum classification

    • Publication forum level 2

    ASJC Scopus subject areas

    • General Computer Science
    • General Materials Science
    • General Engineering


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