Circularly Polarized Antennas Inspired by Dual-Mode SIW Cavities

This paper presents a detailed study on a family of circularly polarized (CP) antennas inspired by the dual-mode substrate integrated waveguide (SIW) cavities. The related design methodology has been proposed and summarized for the first time. The field distribution for dual-mode SIW cavities (using TE
₁₀₂
, TE
₂₀₁
and TE
₁₀₃
modes) are first analyzed. Based on the current flow of the orthogonal modes, slot cuts are incorporated on the top surface considering both the phase and current magnitude, which leads to optimal boresight CP radiation. All the feasible slot combining configurations which are able to generate CP radiation for the dual-mode cavities are summarized and characterized. For experimental verification, four low-profile, low-cost and high- efficiency CP antennas using the dual-mode cavities are proposed, analyzed and implemented, including two CP antennas based on the degenerate TE
₁₀₂
/TE
₂₀₁
half-mode-like resonators, and a CP antenna as well as its 2-element array using the degenerate TE
₁₀₃
/ TE
₂₀₁
dual-mode cavity. The measured and simulated results are in excellent agreement. Useful design guidelines are provided. These antennas show a measured bandwidth varying from 2.0 % to 4.1 % and a peak gain ranging from 7.0 dBic to 9.4 dBic, respectively. They demonstrate good CP performance and high radiation efficiency which is better than 88 % in simulation. They offer attractive features including interesting working principle, easy implementation, low-cost, and non-sensitivity to tolerance, appearing as good candidates for high-frequency directive antenna application.