A Simple and Novel Planar Structure to Excite Characteristic Modes

In this paper a low-profile and novel planar excitation technique is proposed to excite characteristic modes of a patch antenna. The proposed exciter consists of a printed balun and four exciters are positioned at the middle of each side of a square plate. Rectangular and circular slits are incorporated to each side of the square plate to achieve wide band operation. The designed antenna element operates in 24-31 GHz frequency band with VSWR below 2:1 and four different radiation modes can be obtained by exciting the ports with appropriate phase shifts corresponding to the radiation mode of interest. Simplicity of the designed antenna structure enables the utilization of the antenna element in a massive MIMO base station for 5G mmWave applications.