Compact wideband balanced antenna for mobile handsets

A novel miniature balanced mobile handset antenna is presented in this study, which covers digital communication system (DCS) (1710-1880 MHz), personal communication system (PCS) (1850-1990 MHz), universal mobile telecommunications system (UMTS) (1920-2170 MHz) and wireless local area network (WLAN) (2400-2484 MHz) frequency bands. The antenna is a built-in planar dipole with folded structure and with the addition of a dual arm on each half of the dipole. The performance of the antenna is analysed and optimised under certain design constraints. The stability performance of the proposed antenna against proximity effects is evaluated. The effects of the phone user's hand on the return loss and radiation patterns have been characterised by simulation with a simple hand model. A prototype of the proposed antenna is fabricated and tested. A wide bandwidth planar balun is used to feed the wideband balanced antenna from an unbalanced source. The calculated and measured results show good agreement and confirm good wideband characteristics with multiband operation. The specific absorption rate (SAR) performance of the antenna is also studied experimentally by measuring near field exposure. The measured results have shown low induced current in the ground plane and thus confirm minimisation of performance variations and SAR.