Summary
International Symposium on Antennas and Propagation
2008
Session Number:4IS06b
Session:
Number:4IS06b-3
Unbalanced Fed Dipole Antenna Mounted on Ground Plane with L-shaped Parasitic Elements for Mobile Handsets
Youhei OKADA, Manabu YAMAMOTO, Toshio NOJIMA,
pp.-
Publication Date:2008/10/27
Online ISSN:2188-5079
Summary:
With the rapid development of cellular communication, various types of antennas for mobile handsets have been extensively proposed in recent years. If a large current flows on a ground plane on which a mobile handset antenna is arranged, the ground plane as well as the antenna element behave as radiating elements. Thus, degradation of the antenna characteristics occurs when the ground plane is held by a human hand. Using a balance-fed antenna is an effective way of reducing the current flowing on the ground plane and preventing the degradation of the antenna characteristics for the case when the antenna is operated near the human hand or head. For this purpose, various kinds of balance-fed antennas for mobile handsets have been proposed [2], [3]. In order to use a balance-fed antenna, the balun, which is a balanced to unbalanced transformer, needs to be inserted in series with the antenna and the feedline. However, the balun has an insertion loss that leads to the degradation of the antenna efficiency. It is reported that an unbalance-fed dipole antenna mounted on a ground plane can achieve characteristics equivalent to a balance-fed antenna without using the balun [4], [5]. In this paper, an unbalance-fed dipole antenna mounted on a ground plane with L-shaped parasitic elements for the mobile handsets is proposed. It is shown that the current flowing on the ground plane is sufficiently reduced by the use of the parasitic elements. It is also confirmed that the radiation efficiency of the antenna located near a human phantom has improved due to the suppression of the leakage current on the ground plane.