Circularly Polarized Slot Antennas With Dual-Mode Elliptic Cavity

Circularly polarized slot antennas based on dual-mode elliptic substrate integrated waveguide (SIW) cavities are proposed in this letter. Current distribution on the dual-mode cavity is analyzed first to facilitate the layout design. The antennas are divided into three categories. For the first one, three unbalanced slots are etched on the upper surface of the cavity with a central rectangular slot placed perpendicularly to the arc-shaped slots on the two sides of the long axis. For the other two antennas, two pairs of symmetric arc-shaped slots are etched on the upper surface of the cavity. One of them has an additional shorting-pin in the center. Circular polarization is achieved by simultaneously exciting two quasi-TM110cavity modes and combining them in the 5-6 GHz frequency range. The working principle of the dual-mode antennas is theoretically illustrated in detail and experimentally verified. The proposed antennas offer attractive features, including novel working principle, simple structure, low loss, low profile, low cost, and good gain, appearing as good candidates for indoor communication.