Ultra-Wideband and Low-Profile Circularly Polarized Waveguide Antenna Array with Wave-Absorber for mm-Wave Applications

In this paper, an ultra-wideband circularly polarized (CP) waveguide antenna array for millimeter-wave (mm-Wave) communications is presented. The design includes a wideband CP hollow waveguide amplitude element, comprising the retained portion of the broad-wall and notches of the narrow-wall. These structures provide field components parallel to the yoz-plane and xoz-plane, respectively, thereby achieving balanced amplitude and stable 90° phase difference, resulting in a wideband left-handed circularly polarized (LHCP) response. The antenna element exhibits excellent good CP radiation performance across the 19-31 GHz frequency band (Bandwidth:48%). Additionally, a novel structure for wave-absorber, the structure consists of an open circular upper layer for low-frequency wave absorber and a lower layer with a square lattice for high-frequency wave-absorber. Tt is proposed to enhance the CP performance of the antenna array by suppressing radiation aperture coupling. The antenna array is fed by an equal-amplitude, in-phase substrate-integrated coaxial line (SICL) feeding network. A prototype 4 × 4 antenna array with dimensions of 36 × 40 × 25 mm³ has been manufactured and measured, demonstrating operation within the 19-31 GHz frequency range, with a 48% impedance bandwidth and 48% axial ratio (AR) bandwidth. The antenna array achieves a peak gain of 21.9 dBic and an impressive total antenna efficiency of 90%, indicating its suitability for mm-Wave applications. © 2024 IEEE.