Wearable Harmonic Transponder for IoT Applications

The paper presents a novel compact wearable harmonic transponder, composed of a dual-band patch-type antenna loaded by an HSMS-2820 Schottky diode, operated at 869 MHz and 1 734 MHz frequencies. The antenna itself is optimized for a minimum ground plate size. The transponder performance was evaluated both in free space and when attached to a human muscle phantom. The total harmonic transponder conversion loss is 6.2 dB for an excitation power of -25 dBm at the antenna-diode interface, outperforming state-of-the art solutions. The measured reading distances are 9.0 m and 8.8 m for
$\mathbf{EIRP}=20\mathbf{dBm}$
when the transponder is placed in free space and on the human body, respectively. As a means of machine-to-person communication, the transponder is suitable for Internet-of-Things concept.