A New Scheme to Avoid Null Zone for HF-Band RFID with Diversity Combining of Loop Antennas

Hiroshi HIRAYAMA  Nobuyoshi KIKUMA  Kunio SAKAKIBARA  

Publication
IEICE TRANSACTIONS on Communications   Vol.E93-B   No.10   pp.2666-2669
Publication Date: 2010/10/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E93.B.2666
Print ISSN: 0916-8516
Type of Manuscript: Special Section LETTER (Special Section on Advanced Technologies in Antennas and Propagation in Conjunction with Main Topics of ISAP2009)
Category: Antennas
Keyword: 
RFID,  selective diversity,  loop antenna,  wireless power feeding,  

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Summary: 
A new scheme to avoid null zone for HF-band RFID without expanding antenna size is proposed. At first, we demonstrate by FDTD simulation that the null zone occurs because of cancellation of magnetic fields over the loop surface. To prevent cancellation of magnetic fields, the loop antenna is split into four parts, which work as a planar array antenna. The outputs of antennas are gathered by using combining circuit. We have validated by FDTD simulation that the proposed scheme enlarges the worst received power by 13.1 dB.