A Wideband Full-Metal Sidewall-Loaded Magnetoelectric Dipole Array Based on Combined Ridge and Groove Gap Waveguides in the Q-Band
Yaxiang Wu, Takashi Tomura, Jiro Hirokawa, Miao Zhang
Abstract
A wideband full-metal sidewall-loaded magnetoelectric (ME) dipole array antenna fed by a combined ridge–groove gap waveguide (GGW) is proposed. Three promising full-metal aperture-coupled <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times2$ </tex-math></inline-formula> element ME-dipole subarrays are investigated and compared in detail. By introducing sidewalls around the metal pillars and increasing their height to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.36\lambda _{0}$ </tex-math></inline-formula> , the bandwidth of the subarray is substantially enhanced to 33% for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{S}_{11} < -15$ </tex-math></inline-formula> dB. An eigenmode analysis is performed to explain and validate the broadband property of the proposed subarray with taller pins and sidewalls. The combined ridge GW (RGW) and E-plane GGW are employed in the feeding layer for a compact array as well as for lower losses and better isolation between the gap waveguides. Wideband ridge-to-groove (RG) and groove-to-ridge (GR) junctions are designed using stepped transformers for bandwidth enhancement. For verification, an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times8$ </tex-math></inline-formula> element sidewall-loaded ME-dipole array is designed and fabricated by computer numerical controlled (CNC) milling technique in the Q-band. The bandwidth for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{S}_{11} < -10$ </tex-math></inline-formula> dB is widened to 35.9% from 34.5 to 49.4 GHz. From 34.3 to 34.7 and 35.6 to 48.7 GHz, the antenna efficiency is better than 75%, with a bandwidth of 32.5%. The proposed design is attractive for wideband and higher-frequency wireless applications.