A Wideband Circularly Polarized SIW Cavity-Backed Patches Antenna with Air Cavity

A novel single feed wideband circularly polarized (CP) substrate integrated waveguide (SIW) cavity-backed antenna with air cavity is presented in this paper. The proposed structure is mainly composed of two SIW cavities, aperture coupling slot, air cavity, and two patches. The CP operation is achieved by introducing a pair of L-shaped strips to the corners of the lower patch, and embedding a cross-slot on the upper patch. The proposed antenna exhibits a simulated impedance bandwidth (IBW) of 30.89% (13.96 to 19.06 GHz) for
$\boldsymbol{\vert \mathrm{S}_{11}\vert \leq-10}$
dB, a 3-dB axial ratio bandwidth (ARBW) of 14.67% (15.86 to 18.37 GHz) for axial ratio (AR)
$\boldsymbol{\leq 3\text{dB}}$
, and gain of
$\boldsymbol{6.86\pm 0.6\text{dBi}}$
across the 3-dB ARBW. In addition, its AR can be kept below 3 dB over the entire 3-dB beam width. The proposed antenna also has a stable radiation pattern over the entire CP frequency band and exhibits good symmetry in all plane.