Broadband Square Slot Antenna for Circular Polarization with Separated L-Probes and Stubs in the Slot

Ronald JOSEPH  Syuhei NAKAO  Takeshi FUKUSAKO  

IEICE TRANSACTIONS on Communications   Vol.E94-B   No.4   pp.951-959
Publication Date: 2011/04/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E94.B.951
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Antennas and Propagation
circular polarization,  broadband characteristics,  separated L-probes,  reflector,  stubs in the slot,  

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A novel circularly polarized antenna with square slot for broadband characteristics is proposed in this paper. The horizontal and vertical components of the L-shaped probe, which is a key element to generate circular polarization, are separated in the structure, contrary to the concept of joined probes. Another novelty, placing stubs in the slot, which are attached to the ground plane, is proposed to improve the axial ratio (AR) characteristics of the antenna by around 10%. Placing a reflector at a distance of λ0/4 from the antenna to obtain unidirectional patterns is effective when no stubs are placed in the slot. The antenna attains a < 10 dB return loss bandwidth of 47.5% (2.76-4.48 GHz) and < 3 dB axial ratio (AR) bandwidth of 42.47% (2.67-4.11 GHz) in measurement. Parametric studies on key parameters and measured results are also presented.