Switching a dual band PIFA to operate in four bands

Abstract

Competitive global marketing in the mobile phone sector has driven demand for small phone terminals capable of multi-band operation across standard mobile communication bands. There is restriction on the antenna size due to the presence of various integrated components for different applications in contemporary handsets. The antenna should also be reasonably efficient and free of excessive radiation illuminating the user’s head (low SAR value). PIFAs are widely used as an internal antenna solution. They have desirable features such as high efficiency multi-frequency behavior, moderate bandwidth, low profile, low cost, less prone to breakage and reduced user power absorption compared with equivalent external antennas. For US or European GSM systems, the antenna should be matched to either the GSM850 / GSM1900 bands or the GSM900 / GSM1800 bands. The antenna presented here is based on a small [1] dual band PIFA with maximum dimensions 36 mm x 12 mm x 6 mm. This size is typical of a PIFA designed for a contemporary mobile phone. While versitile, at lower frequencies it is often difficult to completely cover the GSM850 and EGSM 900 bands simultanously using a small antenna. In this paper, a PIFA is reported with switches to select between two sets of low and high resonance pairs. The antenna has been designed with the intention to operate in either of the GSM850/GSM1900 and GSM900/GSM1800 band pairs, while being manufactured with standard planar phototihography processes.