Design of Wideband Balanced Folded-Arms Dipole Antenna for Mobile Handsets

Abstract

Investigations of a wideband balanced antenna for mobile handsets covering three bands—GSM1800, GSM1900, and UMTS—are presented. Balanced antennas have advantages in handset applications as they are less affected by juxtaposition with human tissue than unbalanced types. The antenna is a slotted planar dipole with its arms folded and not connected at their ends. The antenna is fed by a balanced voltage source. The antenna impedance was investigated using two different methods, including an S-parameter method and a mirror image method. For the purpose of antenna stability evaluation and power gain measurement, a wide bandwidth planar balun was adopted and modified to feed the antenna from an unbalanced source. For validation, prototypes of the antenna were fabricated and tested. The calculated and measured results in terms of return loss show good agreement and the results also show good wideband characteristics.

Keywords:

• balanced antenna
• planar dipole
• wide bandwidth
• mobile handset

Acknowledgment

The authors gratefully acknowledge the financial support from the UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1.