Proximity-Fed MIMO Antenna with Two Printed Ifas and a Wideband T-Shaped Neutralization Line
A proximity-fed MIMO (multiple-input-multiple-output) antenna with two printed IFAs (inverted-F antennas) and a wideband T-shaped neutralization line is presented. Each element printed IFA is fed by a proximity-fed structure which provides a parameter to control the return loss without effect on the isolation of the two IFAs. The wideband T-shaped neutralization line, which consists of two meandered branches and a rectangular grounded branch, can enhance the isolation of the two IFAs over a wide operation band (2.35-3.75 GHz). The two meandered branches are connected to the two IFAs, respectively, and the rectangular branch is connected to the ground plane. There are two parameters to adjust the isolation without effect on the return loss. Therefore, the operational bandwidth and the isolation of the proposed antenna can be controlled independently. A bandwidth of 46% with VSWR ≤ 2 and isolation ≥ 20 dB from 2.35 to 3.75 GHz is achieved. The MIMO antenna of compact size 40 x 14 mm2 is suitable for application in mobile phones. Moreover, the ground plane size can be changed for applying the proposed antenna in different handsets. The results, including S-parameters, radiation pattern, mean effective gain (MEG), radiation efficiency, complex correlation coefficient and the effects of human hand and head, indicate the proposed MIMO antenna can provide spatial and pattern diversity.