Realization of a Beam-Tilted Circularly Polarized Corporate-Fed Waveguide Slot Array in the 60 GHz Band

Abstract

A beam-tilted circularly polarized (CP) corporate-fed waveguide slot array is accomplished in the 60 GHz band. The main beam tilting in the 45° cut-plane is achieved by introducing a corporate feeding circuit with a linearly tapered phase distribution. The T- and H-junctions with nonidentical output waveguide widths are newly proposed to realize progressive output phases. By cascading asymmetric T- and H-junctions into a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$16\times16$ </tex-math></inline-formula> way power divider, we design a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$32\times32$ </tex-math></inline-formula> element array consisting of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$256\,\,2\times 2$ </tex-math></inline-formula> element CP subarrays. The simulated tilt angle coincides with the theoretical one over the whole frequency band. The test antenna is fabricated by the diffusion bonding of thin copper plates. Stable beam directions and wideband operations are verified by the experimental evaluations. The overall reflection is sufficiently suppressed below −14 dB over the 56–67 GHz frequency band. The realized gain higher than 37 dBic is achieved over the frequency range of 59–64 GHz, while the AR is suppressed below 3.5 dB over the frequency range of 57.25–66.75 GHz.