Design of Circularly Polarized and Electrically Small Antenna with Omnidirectional Radiation Pattern


IEICE TRANSACTIONS on Communications   Vol.E97-B   No.12   pp.2739-2746
Publication Date: 2014/12/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E97.B.2739
Type of Manuscript: PAPER
Category: Antennas and Propagation
electrically small antenna,  circular polarization,  omnidirectional radiation pattern,  

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This paper presents an electrically small and circularly polarized antenna with an omnidirectional radiation pattern. The antenna consists of a horizontal loop element enclosed by two U-shaped elements and a vertical element from the feeding point. The radiation pattern of the circular polarization is omnidirectional and has a maximum gain of -2dBic in parallel to the ground plane at the 900MHz band. The antenna dimensions are 48 × 20 × 13.8mm (0.14λ × 0.06λ × 0.04λ) with ka =0.476 (i.e. < 0.5), where k is the wavenumber at the resonant frequency and a is the radius of a sphere surrounding the antenna. The dimension corresponds to the definition of an electrically small antenna. The omnidirectional circularly polarized pattern of a prototype antenna shows good agreement with that of the simulation. In addition, this paper introduces a mechanism that generates omnidirectional circular polarization from electrically small antennas.