ScienceAsia 27 (2001) : 285-291 |doi: 10.2306/scienceasia1513-1874.2001.27.285

A Bidirectional Antenna Using
a Probe Excited Rectangular Ring

Sompol Kosulvit, Chuwong Phongcharoenpanich^* and Monai Krairiksh

ABSTRACT: This paper presents a simple and cost-effective bidirectional antenna using a probe excited rectangular ring. Radiation characteristics, such as radiation pattern and directivity, and impedance of this antenna are investigated. Radiated fields are calculated from the Fourier transform of the aperture field that is derived from the field inside the ring by using Green’s function. Impedance of this antenna is realized by using induced EMF method. The impedance of a probe with optimum ring length that provides the single mode is firstly determined. Then, the resultant input impedance of the antenna is the reciprocal of the combination of the probe admittance and the both apertures admittance. From our investigations, for a specific ring dimension, the optimum ring length that yields the maximum directivity is calculated and chosen as a design parameter. Experimental results, verifying the bidirectional radiation pattern and impedance, agree very well with the theoretical predictions. This antenna is suitable to be a bidirectional base-station antenna in a street cell.

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Faculty of Engineering and Research Center for Communications and Information Technology King Mongkut’s Institute of Technology Ladkrabang, Bangkok 10520, Thailand.

* Corresponding author, E-mail: kpchuwon@kmitl.ac.th

Received 21 Aug 2000, Accepted 25 Jun 2001