A novel broadband omnidirectional dual polarized MIMO antenna for 4G LTE applications

A low-profile broadband omnidirectional multiple-input and multiple-output (MIMO) antenna with dual polarization is presented, which provides polarization diversity for the 4G Long Term Evolution (LTE) communication systems, networks, and base stations. It consists of two orthogonally polarized radiating elements with separate feeds. The horizontally-polarized element is comprised of four pairs of flag-shaped dipoles, four parasitical strips, and a balun with tapered striplines for balance-unbalance transition. It has a fractional bandwidth of 55% covering from 1.7 GHz to 3.0 GHz with return loss greater than 10 dB and an overall size of 43×43×1.6 mm³. The vertically polarized element consists of a discone antenna, a round sleeve, and a top-loading ring shorted to the ground-plane for bandwidth enhancement. It has a fractional bandwidth of 137% covering from 671 MHz to 3580 MHz, and an overall volume of 170×170×56 mm³. The measurement results show both antenna elements exhibit smooth gain over the operational bandwidth. In addition, the geometrical shape and compactness of the proposed design, along with the omnidirectional radiation patterns, makes it ideal for ceiling or surface-mounted 4G LTE applications.