Slit-Slot Line and Its Application to Low Cross-Polarization Slot Antenna and Mutual-Coupling Suppressed Tripolarized MIMO Antenna

A slit-slot transmission line is devised, investigated, and applied to a slit-slot antenna and a co-located tripolarized slit-slot antenna array for 2.45 GHz multipolarization multi-input-multi-output (MIMO) applications. The slit-slot transmission line, with slit array etched on its conductive planes, is analyzed and characterized by using an equivalent circuit model and a graphical method based on simulations. Taking advantage of the features of a slit-slot transmission line, which include a shorter wavelength and a favorable current distribution for antenna applications, a slit-slot antenna, and a co-located tripolarized slot antenna array are presented and investigated by simulations and experiments. The effects of slits on the performances of the slit-slot antenna and the antenna array are explained. The simulated and measured results of fabricated prototypes show that the slits improve the cross-polarization of both the slit-slot antenna element and the antenna array around 5 dB, and that the isolation among the tripolarized slit-slot antenna array is improved by 14 dB, compared to the associated slot antennas. Furthermore, tripolarized slit-slot antenna array has an omnidirectional radiation patterns and low correlation which are favorable for MIMO applications.