Compact Inkjet-Printed Flexible MIMO Antenna for UWB Applications

In this paper, a miniaturized fully inkjet-printed flexible multiple-input-multiple-output (MIMO) antenna for ultrawideband (UWB) application is proposed, occupying a compact size of $22\times 31\times 0.125$ mm³. In the proposed antenna, two half-planar radiators are introduced to minimize the antenna size. Moreover, a modified T-shaped stub is employed on the ground plane to improve the impedance performance. In addition, a slot is etched on this modified T-shaped ground stub to further enhance the isolation. By doing so, the proposed antenna can operate from 2.9 to more than 12 GHz with the mutual coupling less than −15 dB. Furthermore, to address the out-of-band characteristic drawback that existed in most of the previous UWB antenna, a parallel coupled band-pass filter with stepped impedance transformation and defected ground structure is incorporated in the feedline of the antenna to achieve sharp rejection at the edges of the UWB band. The measurements indicate that the proposed filter-antenna can cover from 3.43 to 10.1 GHz, with the envelope correlation coefficient below 0.3 and the channel capacity loss below 0.4 bit/s/Hz, which ensures its good MIMO performance.