Design of a Low-Profile Tripolarized Antenna With Wide Bandwidth

In this paper, a low-profile tripolarized antenna with the wideband operation is presented. It includes a monopolar patch element for vertically linear polarization (LP) omnidirectional radiation in the horizontal plane and two orthogonal dipoles for x- and y-direction LP broadside radiations. In order to achieve the wideband, nevertheless keeping the low-profile, the monopolar patch antenna is coupled with an annular ring, while the two orthogonal dipoles are incorporated with a metasurface. Optimized design with a profile of 0.09λ
_min
(λ
_min
is the free space wavelength referring to the lowest operational frequency) has been fabricated and measured. The measurements result in an overlapped bandwidth of 24.45% (2.19-2.80 GHz) for reflection coefficient <; -10 dB and coupling coefficients of <; -30 dB among the three ports. In addition, the antenna yields measured peak gains of 8.4 and 9.5 dBi in monopolar mode and two broadside modes, respectively.