A Low-Profile Wideband Tripolarized Antenna

As a combination of three orthogonal dipoles, the tripolarized antenna has been demonstrated to significantly improve signal quality in scattering environment. In this communication, we propose a low-profile tripolarized antenna with wideband characteristics. The tristate includes 0° and 90° linear polarizations (LP) with the main beam at broadside and a vertically LP with omnidirectional pattern in the azimuth plane. The design consists of a monopolar patch and two orthogonal dipoles. The wideband performance for the monopolar patch is obtained from two nearly overlapped radiating modes controlled by an array of shorting wires. For the two orthogonal dipoles, the antenna profile is reduced with the effect of parasitic patches. One of the key design features is to utilize the shorting wire in the monopolar patch to feed the dipoles, allowing a simple design and avoiding any feeding network. The concept is experimentally verified with a prototype exhibiting an overlapped bandwidth of 14% with a low profile of <inline-formula> <tex-math notation="LaTeX">$0.09\lambda $ </tex-math></inline-formula>, where <inline-formula> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> is the free-space wavelength at the lowest operating frequency. The measured peak gain in two broadside modes and in monopolar mode are 10 and 7.5 dBi, respectively. Measured isolation between any port is better than 31 dB in the whole frequency range.