Open AccessEfficient NFC coil antennas for fully enclosed metallic‐framed wearable devices
Author(s) -
Choi Jaehyun,
Lim Sangho,
Hong Wonbin
Publication year - 2020
Publication title -
iet microwaves, antennas and propagation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.555
H-Index - 69
eISSN - 1751-8733
pISSN - 1751-8725
DOI - 10.1049/iet-map.2019.0451
Subject(s) - near field communication , electromagnetic coil , wearable computer , inductive coupling , electrical engineering , frame (networking) , coupling (piping) , power (physics) , computer science , wearable technology , power consumption , smartwatch , phase (matter) , electronic engineering , topology (electrical circuits) , engineering , embedded system , mechanical engineering , ultra high frequency , telecommunications , physics , quantum mechanics
This study reports methods of alleviating the effect on inductive near‐field communication (NFC) coils caused by fully enclosed metallic‐frames for wearable devices such as smartwatches. Two techniques that, respectively, involve creating two short‐circuit passages to modify the distribution of the out‐of‐phase current on the metallic‐frame and reducing the out‐of‐phase current amplitude by devising an asymmetric coil topology is presented and studied in detail. Extensive simulation, prototyping and measurement are carried out for 13.56 MHz NFC applications. The presented techniques can, respectively, improve the induced magnetic coupling by 43 and 30% under identical conditions in the presence of the metallic frame. Furthermore, both methods comply with the NFC forum certification and do not require the need to increase the drive current and power consumption of the NFC circuitry.