A Wideband Full-Metal Sidewall-Loaded Magnetoelectric Dipole Array Based on Combined Ridge and Groove Gap Waveguides in the Q-Band

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 $2\times2$ element ME-dipole subarrays are investigated and compared in detail. By introducing sidewalls around the metal pillars and increasing their height to $0.36\lambda _{0}$ , the bandwidth of the subarray is substantially enhanced to 33% for $\text{S}_{11} < -15$ 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 $8\times8$ element sidewall-loaded ME-dipole array is designed and fabricated by computer numerical controlled (CNC) milling technique in the Q-band. The bandwidth for $\text{S}_{11} < -10$ 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.