A Small Printed Inverted-F Antenna for Circular Polarization

Takafumi FUJIMOTO  Keigo SHIMIZU  

Publication
IEICE TRANSACTIONS on Communications   Vol.E102-B   No.2   pp.197-204
Publication Date: 2019/02/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2018ISP0005
Type of Manuscript: Special Section PAPER (Special Section on Recent Progress in Antennas and Propagation in Conjunction with Main Topics of ISAP2017)
Category: Antennas
Keyword: 
printed inverted-F antenna,  circular polarization,  bandwidth,  ISM band,  

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Summary: 
In this paper, a printed inverted-F antenna for radiating circularly polarized wave around its resonant frequency is proposed. To get good axial ratio at the frequency band with 10dB-return loss, a rectangular element is loaded at the feeding line perpendicularly. The axial ratio and the frequency giving the minimum axial ratio can be adjusted by the ratio of the length to the width of the whole antenna and by the dimension of the loaded rectangular element. The operational principle for circular polarization is explained using the electric current distributions. Moreover, the approach of the enhancement for the bandwidth is discussed. The simulated and measured bandwidths of the 10dB-return loss with a 3dB-axial ratio are 2.375GHz-2.591GHz (216MHz) and 2.350-2.534GHz (184MHz), respectively. The proposed antenna's dimension is 0.067λ2cc is the wavelength at the center frequency). The proposed antenna is compact and planar, and is therefore useful for circular polarization in the ISM band.