Coupled‐fed tri‐band MIMO mobile antenna for WWAN and LTE applications

In this paper, a coupled‐fed tri‐band multiple‐input‐multiple‐output (MIMO) mobile antenna is proposed for WWAN and LTE applications. The MIMO antenna system is composed of two antenna elements and they are oriented diagonally at the non‐grounded portion of the FR‐4 substrate. Each antenna element consists of a planar inverted‐F antenna (PIFA) coupled‐fed by a L‐shaped driven strip monopole. By adding a parallel‐resonant spiral slit in the main ground, the bandwidth of the lower band can be enhanced to cover the whole GSM850 and GSM900 bands without increasing the antenna size. Slits embedded on the ground are employed to enhance port isolation between the antenna elements. The proposed antenna provides triple bands including the lower band of 810–965 MHz, middle band of 1560–3320 MHz, and upper band of 3400–3590 MHz for WWAN and LTE applications. Detailed geometry and working mechanisms of the antenna are presented.