An Investigation on Self-Resonant and Capacitor-Loaded Helical Antennas for Coupled-Resonant Wireless Power Transfer

Hiroshi HIRAYAMA  Tomohiro AMANO  Nobuyoshi KIKUMA  Kunio SAKAKIBARA  

IEICE TRANSACTIONS on Communications   Vol.E96-B    No.10    pp.2431-2439
Publication Date: 2013/10/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E96.B.2431
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Recent Progress in Antennas and Propagation in Conjunction with Main Topics of ISAP2012)
Category: Antennas
wireless power transfer,  coupled resonant,  helical antenna,  self resonance,  

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Self-resonant helical antenna and capacitor-loaded helical antenna of the same dimension for coupled-resonant wireless power transfer is discussed. At first, fundamental difference of the self-resonant and the capacitor-loaded antenna is demonstrated by calculating electric- and magnetic-coupling coefficient. Next, performance of the helical antennas are discussed from viewpoints of 1) transmission efficiency, 2) undesired emission, 3) near-field leakage, 4) effect of human body and 5) effect of conductivity. We have found that the self-resonant helical antenna has an advantage in low transmission loss due to a conductivity of wire. On the other hand, the capacitor-loaded antenna has an advantage in low emission, long transfer distance, and low influence of resonant frequency from human body. This is because both electric-field coupling and magnetic-field coupling are dominant for the self-resonant antenna while only magnetic-field coupling is dominant in the capacitor-loaded antenna.