Planar integrated substrate integrated waveguide circularly polarized filtering antenna

A new design of substrate integrated waveguide (SIW) circularly‐polarized (CP) filtering antenna is presented, which is based on dual‐mode (TE₁₀₂ and TE₂₀₁) cavities. The satisfying filtering performance of the antenna is realized by a coupled‐resonator circuit of two dual‐mode SIW cavities. And the radiating element of the antenna is a cavity‐backed CP slot antenna which is formed by a nonuniform ring slot integrated with the back cavity. To demonstrate the idea, a prototype antenna operating at X band is designed, fabricated, and measured. Measured results show that the 10‐dB impedance bandwidth is 4.2% (from 11.6 to 12.1 GHz), the 3‐dB axial‐ratio (AR) bandwidth is 4%, and the gain is 5.6 dBi at the center frequency of 11.8 GHz.