Dual‐band design and decoupling between two planar inverted‐F antennas using linear parasitic elements and bridge line

Abstract

In this study, a simple technique is proposed to simultaneously achieve dual-band characteristics and low mutual coupling between two planar inverted-F antennas (PIFAs), which is one of the most popular antennas used in handset terminals such as mobile phones. The PIFAs initially operate only at a single band at 2.0 GHz (UTMS band). Although several solutions have been proposed to increase the operating frequency band as well as reduce the mutual coupling between multiple-input multiple-output antennas, most of them require adjustment of the original antenna size or configuration. This would be disadvantageous if these methods are applied under design conditions that hinder the adjustment of the original antenna. The proposed method uses a combination of linear parasitic elements (LPEs) and a bridge line (BL) and then loads them onto PIFAs. The loading of LPEs increases the operating frequency band at 2.4 GHz, which can help the PIFAs achieve dual-band operation. Furthermore, the BL transmits opposite-phase currents to cancel the coupling current between the two PIFAs. Consequently, the mutual coupling can be reduced to less than −10 dB in the dual band without having to adjust the original PIFAs.