Microwave Millimeter Wave Circularly Polarized Antenna Based on SIW Circular Cavity

In this paper, a microwave millimeter-wave circularly polarized antenna based on a SIW circular cavity is presented. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$T M_{020}$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$T M_{120}$</tex> modes of the SIW circular cavity are excited in the millimeter-wave band by a coupling slit, which gives the millimeter-wave band a dual-frequency characteristic, and are fed using a sequential rotation technique, thus realizing a dual-frequency broadband millimeter-wave circularly polarized antenna. In addition, the top metal layer of the SIW millimeter-wave array is multiplexed as a radiating patch for the microwave band, which is fed by a quadrature-fed patch, thus generating circularly polarized radiation in the microwave band. Experiments show that the antenna operates over the microwave band (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$4.61-4.86 \text{GHz}$</tex>) and millimeter-wave bands (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$25-33 \text{GHz}, 34-39.4 \text{GHz}$</tex>), with axial ratio bandwidths of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$4.78-4.89 \text{GHz}$</tex> (2.3%), <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$26.2-33 \text{GHz}$</tex> (23%), and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$35.1-39.1 \text{GHz}\ (10.8 \%)$</tex>, respectively. The present antenna can provide an optional solution with high feasibility and application potential for wireless communication applications.