Summary
International Symposium on Antennas and Propagation
2009
Session Number:2B1
Session:
Number:2B1-5
Bandwidth Characteristic of Low-Profile TopLoaded Monopole Antenna with Folded Rim
Woo-jin Kim, Naobumi Michishita, Yoshihide Yamada,
pp.365-368
Publication Date:2009/10/21
Online ISSN:2188-5079
Summary:
A radio-on-fiber system has been developed for enabling cellular mobile communication in radio-blind areas, such as highway tunnels and underground shopping malls [1], [2]. A distributed antenna system consisting of coaxial cables and couplers has been specifically designed for use in the aforementioned radio-blind areas [2], [3]. In an in-building antenna distribution system, the antenna is installed on the ceiling, and the hence a low-profile antenna is preferred. A top-loaded monopole antenna (TLMA) has been developed for use as a low-profile antenna. The TLMA that arranged with shorting cylinder or pins has a feature of low profile and the vertical polarization antenna by exciting TM01 mode [4], [5]. For bandwidth enhancement, triangular or trapezoidal plates are used as the radiating elements for the TLMA [6]. Based on them, TLMA was designed, and clarified impedance-matching techniques for and the bandwidth characteristics of a TLMA with oblique shorting pins, and the effects of the rim at the edge of the finite ground plane are also clarified [7]. However, the broadband characteristics cannot be achieved when the antenna height is less than 0.04λ. This paper presents the bandwidth characteristics as variable size of finite ground plane. And, the bandwidth characteristics, when the folded rim is arranged, are also investigated. As a result, this shape is similar to cylindrical cavity resonator. Finally, the simulation results of the TLMA with folded rim are verified through measured impedance characteristics and radiation patterns