Compact MIMO PIFA for LTE/ WWAN operation in the mobile application

In this article, a multiple input multiple output (MIMO) antenna for LTE/WWAN mobile application is proposed. The designed MIMO antenna consists of two symmetric coupled-fed antenna elements which are disposed on the corners of the long edge of the system circuit board. Each of the two antenna elements occupies a small area of 13×35mm², which is small enough to be incorporated in a mobile MIMO terminal. The proposed antenna element has a simple structure of comprising a shorting strip of length about λ/8 at 1760 MHz with a tuning stub connected to it and a simple inverted-L feeding strip to capacitively excite the shorting strip. As a result, a wide operating band to cover GSM1800/1900/UMTS2100/LTE2300/ 2500 operation is obtained with desired 2:1 VSWR, and the measured isolation value (S21) between the two antenna elements is lower than -15dB. The MIMO antenna system is an all-printing structure with low production cost, which is especially suited for thin-profile mobile terminals.