Design and analysis of flexible embroidered UHF-RFID tag on facemask for IoT applications using characteristics mode analysis

This work presents an ultra-high frequency (UHF) radio frequency identification (RFID) tag embroidered on a face mask for Internet of Things (IoT) devices. The tag is designed and optimized to operate within the entire US RFID band of 902-928 MHz using characteristic mode analysis (CMA). A Mickey Mouse (MM) shaped radiation element is analyzed by testing three resonating modes at frequency of 900 MHz. Additionally, two dipoles are introduced to achieve the optimal conjugate match with a passive RFID chip (Alien Higgs H3), which exhibits an impedance of 27-200j at the desired frequency. A simulation of the voxel head model has also been carried out to verify the specific absorption rate (SAR), which provides SAR <1.43 W/kg. The proposed tag is embroidered on a cotton fabric facemask with a dielectric constant of 1.143 using conductive thread with a resistance of 28 O/ft. This tag features a good impedance match in US RFID band along with gain of 2.06 dB and a 37% reduction in size as compared to the previous version. Furthermore, it provides a read range of 3 m for an off-body scenario and 2.5 m for an on-body scenario. The proposed wearable facemask tag has potential applications for various real-life applications.