The design of broadband omnidirectional horizontally polarized dipole antennas with branch lines

Abstract

ABSTRACTIn this article, a broadband omnidirectional horizontally polarized dipole antenna with branch lines is proposed. The proposed antenna consists of a dipole element with T‐shaped branch lines arranged in a circle in four directions on one microstrip substrate; power is supplied through an integrated balun. To check the broadband characteristics of this antenna, its radiation characteristics were examined while changing the width of the feed line, the distance between the dipole antenna and the branch line, the length of the branch line, and the distance between branch lines. As a result, the return loss in a structure with no branch line was −10 dB or less in the 16% band of 1.7–2 GHz, but in the structure with branch lines, it was −15 dB or less in the 38% band of the PCS/IMT/WLAN (1.7–2.5 GHz), which is broader by about 500 MHz than in a conventional antenna. The gain of the proposed antenna was atleast 1 dBi in the band used. The proposed antenna has a thin profile, as it consists of a single substrate. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2901–2905, 2015