Summary
International Symposium on Antennas and Propagation
2008
Session Number:2C16
Session:
Number:2C16-1
Polarization and Multi-Band Characteristics of Loaded Microstrip Square Ring Antennas
Lotfollah Shafai, Saeed I. Latif, Soon-Soo Oh,
pp.-
Publication Date:2008/10/27
Online ISSN:2188-5079
Summary:
Microstrip square ring antennas are recently studied extensively because of their attractive features such as compactness, ease of fabrication, usefulness in arrays etc. Its resonant wavelength for the dominant mode TM11 is approximately equal to the average circumferential length of the square ring. Therefore, the antenna size is much smaller than that of the regular microstrip antenna [1]. The width of the conducting strip of the ring antenna determines the frequency of operation of this antenna. As the width is made narrower, the resonance frequency goes down, however, at the expense of high input impedance. Capacitive feeding has been proposed to improve the matching [2]. Different types of loading, e.g. stub, notch, gap, shorting post etc., also help improve the impedance matching [3, 4]. However, the loading contributes to the increase in the cross-polar level. Moreover, an interesting phenomenon has been observed when the square ring antenna is loaded with a narrow gap. Several additional resonances become excited along with the unloaded mode, with one at a much lower frequency than that of the unloaded mode. The multi-frequency capability of the loaded square ring antenna, along with its polarization characteristics will be discussed in this paper.