Compact, Highly Efficient, and Fully Flexible Circularly Polarized Antenna Enabled by Silver Nanowires for Wireless Body-Area Networks

• Published in: IEEE transactions on biomedical circuits and systems Vol. 11; no. 4; pp. 920 - 932
• Main Authors: Zhi Hao Jiang, Zheng Cui, Taiwei Yue, Yong Zhu, Werner, Douglas H.
• Format: Journal Article
• Language: English
• Published: United States IEEE 01.08.2017; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Anisotropy; Antenna radiation patterns; Body area networks; Circular polarization; Electromagnetic Radiation; Equipment Design; Form factors; Ground plane; Humans; Linear polarization; Loaded antennas; Nanotechnology; Nanowires; Off-body communications; Patch antennas; Polarized radiation; Polydimethylsiloxane; polydimethylsiloxane (PDMS); Radiation; Robustness (mathematics); Silicone resins; Silver; silver nanowires (AgNWs); Substrates; wearable antenna; Wearable Electronic Devices; Wearable technology; wireless body-area networks; Wireless communication; Wireless networks; Wireless Technology
• ISSN: 1932-4545; 1940-9990
• DOI: 10.1109/TBCAS.2017.2671841

A compact and flexible circularly polarized (CP) wearable antenna is introduced for wireless body-area network systems at the 2.4 GHz industrial, scientific, and medical (ISM) band, which is implemented by employing a low-loss composite of polydimethylsiloxane (PDMS) and silver nanowires (AgNWs). The circularly polarized radiation is enabled by placing a planar linearly polarized loop monopole above a finite anisotropic artificial ground plane. By truncating the anisotropic artificial ground plane to contain only 2 by 2 unit cells, an integrated antenna with a compact form factor of 0.41λ 0 × 0.41λ 0 × 0.045λ 0 is obtained, all while possessing an improved angular coverage of CP radiation. A flexible prototype was fabricated and characterized, experimentally achieving S 11 <;- 15 dB, an axial ratio of less than 3 dB, a gain of around 5.2 dBi, and a wide CP angular coverage in the targeted ISM band. Furthermore, this antenna is compared to a conventional CP patch antenna of the same physical size, which is also comprised of the same PDMS and AgNW composite. The results of this comparison reveal that the proposed antenna has much more stable performance under bending and human body loading, as well as a lower specific absorption rate. In all, the demonstrated wearable antenna offers a compact, flexible, and robust solution which makes it a strong candidate for future integration into body-area networks that require efficient off-body communications.