Ultra Low Profile Dipole Antenna with a Simplified Feeding Structure and a Parasitic Element

Arpa THUMVICHIT  Tadashi TAKANO  Yukio KAMATA  

Publication
IEICE TRANSACTIONS on Communications   Vol.E89-B   No.2   pp.576-580
Publication Date: 2006/02/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e89-b.2.576
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Antennas and Propagation
Keyword: 
low profile,  horizontal dipole,  impedance matching,  parasitic element,  conductor plane,  

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Summary: 
This study is devoted to a half-wave dipole with a conductor plane at a distance much smaller than a quarter wavelength which we designate as an ultra low profile dipole (ULPD) antenna in this paper. The concerns of ULPD antenna are the feeding method and the impedance matching, because the input impedance usually tends to be lowered by the existence of a metallic structure in its proximity. In this paper, we propose a ULPD antenna with an excellent impedance matching and a coaxial feed built within the antenna structure so that the external matching and a balun are not required. A coaxial cable is used as a feed line and extended to be a half of a half wavelength dipole. The other half is made up of a parasitic element, which is connected to the outer conductor of the coaxial radiator. To make a matching, the outer conductor of the coaxial radiator is stripped off at a suitable length, and the total length of a dipole is considered for its resonance at a desired frequency of 2 GHz. The experiment has been conducted. The results show the return loss of -27 dB and the maximum gain of 9 dBi in the normal direction to the conductor plane. The computational results are also obtained, which agree well with the experimental results.