A Low-Profile Wideband Circularly Polarized Filtering Antenna Based on SIW Cavity $\text{TE}_{110}$ Mode for Millimeter-Wave Applications

This letter introduces a circularly polarized (CP) filtering antenna that utilizes a substrate integrated waveguide (SIW) cavity to achieve wideband filtering characteristics. The antenna consists of a stacked patch, a radiating patch, a resonance excitation patch (REP), a SIW cavity, and four shorting pins. The stacked patch and the radiating patch together provide the CP performance. The REP is employed to excite the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\rm {TE}_{110}$</tex-math></inline-formula> mode of the SIW cavity, thus realizing a filtering response. In addition, to suppress high-order modes that appear at higher frequencies, four shorting pins are embedded within the SIW structure, significantly suppressing unwanted radiation. Measured results indicate that an impedance bandwidth of 14.1% (23.5GHz to 27.1GHz), a 3dB axial ratio (AR) bandwidth of 10.9% (23.75GHz to 26.5GHz), and a peak gain of 6 dBi have been achieved. Thanks to the REP and SIW cavity, the proposed antenna shows excellent filtering performance. Featuring the merits of outstanding filtering response, stable and wideband CP radiation, easy integration, and low profile, the proposed antenna is promising for high-speed millimeter-wave applications.