A Low-Profile Broadband Dual-Polarized Omnidirectional Antenna with Low Gain Variations for 5G Indoor Mobile Communications

A low-profile broadband dual-polarized omnidirectional antenna with low gain variations (GV) for 5G indoor mobile communications is presented. A vertical-polarized (VP) antenna element is composed of a pair of orthogonal conical plates and a top-loaded circular brass disc to broaden the impedance bandwidth. A horizontal-polarized (HP) element is consisted of four printed dipoles with rectangular etched slot and parasitic patches around the dipoles to broaden the operating bandwidth, and a 1-to-4 power divider feeding network on the bottom. The feeding network with the balun of “T”-shaped with terminated shorting-circuit via to improve the isolation between the VP and HP elements. Two pairs of extending strips printed along the ±45° direction are used to reduce the GV and broaden the impedance bandwidth. The antenna achieves a compact size of 110mm*110mm*40mm, and the height is only 0.26λ
min
(λ
min
which is the free-space wavelength at the minimum operating frequency). The overlapped bandwidth of 76% (1.69-3.75GHz) with an excellent port isolation (> 28dB) is achieved. Satisfactory omnidirectional radiation characteristics are obtained for both the VP and the HP elements, the GV of the VP element is less than 2 dB, and the GV of the HP element is less than 2.5 dB.