A Dual-Polarized Omnidirectional Metasurface Antenna Designed via Characteristic Mode Analysis

A low-profile dual-polarized (DP) omnidirectional metasurface antenna is proposed in this letter. By conducting characteristic mode analysis on a metasurface, one mode with a vertically polarized (VP) omnidirectional radiation pattern and another one with a horizontally polarized (HP) counterpart are first found. To allow for an easy excitation, a method that can independently manipulate both modes is then developed. After optimization, the VP modal current concentrates at the center of the metasurface, whereas the HP modal current mitigates to the edges of the metasurface. As a result, the two modes can be excited simultaneously with a simple feeding strategy, namely, a central probe is used to excite the VP mode, and four slots under the four edges of the metasurface are used to excite the HP mode. To verify the design, a prototype is simulated, fabricated, and measured. The results show that the proposed antenna achieves a DP omnidirectional radiation with a wide bandwidth of 39.4% and high port isolation of 32 dB.