Hybrid Metamaterial-TL-Based, Low-Profile, Dual-Polarized Omnidirectional Antenna for 5G Indoor Application

A novel hybrid metamaterial-transmission line (TL)-based dual-polarized omnidirectional antenna with a low profile and high port isolation for 5G indoor applications is proposed. A compact shared aperture hybrid metamaterial-TL structure is first proposed, which is carefully analyzed by dispersion curves and current distribution. The hybrid metamaterial-TL structure consists of a mushroom-like composite right/left-handed TL (CRLH-TL) and a ring-shaped mu-negative TL (MNG-TL), forming a pair of orthogonal zeroth-order resonant (ZOR) modes. The shunt ZOR mode of the CRLH-TL structure is successfully excited, which radiates vertically polarized (VP) waves. Horizontal polarization (HP) is realized by exciting a series ZOR response from the ring-shared MNG-TL. By simultaneously exciting two orthogonal ZOR modes, a dual-polarized (VP and HP) omnidirectional antenna with high isolation and good roundness is designed and fabricated. With a low profile of
$0.06\lambda _{0}$
, this dual-polarized antenna shows a measured overlapped −10 dB bandwidth of 14.1% (3.3–3.8 GHz), a port isolation larger than 39 dB, radiation efficiency higher than 80%, and cross pol. levels lower than −18 dB. It demonstrates the advantages of low profile, compact size, high isolation, good bandwidth, and radiation performance, and simple design for 5G indoor microcell, router, multi-input–multi-output (MIMO), or in-band full duplexing applications.