2-Port DL-MIMO Antenna Design for LTE-Enabled USB Dongles

A geometrically symmetric 2-port downlink (DL)- multiple-input-multiple-output (MIMO) antenna for Universal Serial Bus (USB) dongles is described. The design makes use of a center-tapped inductance to independently excite both the common mode and the differential mode. The solution allows for separate, mutually independent, common-mode and differential- mode matching networks. So as to maximize bandwidth and efficiency of the differential mode, the antenna physical structure is designed for maximum occupation of the very small available volume using two symmetric elements each comprising a helix loaded at its end with a capacitive plate. Fabricated prototype of the antenna features higher than 7 dB return loss (RL) and higher than 17 dB isolation in Evolved Universal Terrestrial Radio Access (E-UTRA) band class (BC) 13 and BC 17 and total efficiency higher than 50%.