SIW-Based Circular Cavity-Backed Slot Antenna for Vehicle to Vehicle and 5G Applications

A low-profile circular substrate integrated waveguide (SIW) cavity-backed slot antenna is designed and tested in this manuscript for millimeter-wave (mm-wave) vehicle-tovehicle (V 2 V) and fifth-generation (5 G) applications. The design comprises a circular cavity resonator using SIW technology, inside which an X-shaped slot is etched at the center. The cavity is designed to radiate at 28.22 GHz, and the slot improves its radiation characteristics. An inset feed is used in the feeding section to get the impedance matching at the operating band. The design antenna is simulated, fabricated, as well as, tested with a substrate thickness of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{1. 5 2 4 ~ m m}\left(\mathbf{0. 1 4} \lambda_{0}\right)$</tex>. The geometry exhibits a measured fractional impedance bandwidth (IBW) of 3.86 %, a simulated gain of 6.52 dBi at the end-fire direction, a radiation efficiency of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{9 4. 1 7 \%}$</tex>, a cross-polarization level below <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$-\mathbf{3 7. 7 ~ d B}$</tex>, and a front-to-back ratio of 10.20 dB at the center frequency of 28.22 GHz.