A Half-Mode Gap Waveguide With High-Density Mushroom-Type AMC Enabling High Assembly Tolerance At Millimeter Waves

Journal article, 2026

This paper presents a half-mode groove gap waveguide (HM-GGW) employing a high-density mushroom-type artificial magnetic conductor (AMC) to achieve robust millimeter-wave transmission with low phase sensitivity to assembly misalignment. Conventional HM-GGW structure using low-density pin suffer from pronounced phase variations due to the imperfect approximation of a perfect magnetic conductor (PMC). By reducing the unit-cell period, the proposed high-density mushroom-type AMC effectively suppressing misalignment-induced phase perturbations. A W-band 1-to-2 power divider prototype is fabricated for validation. Measurements demonstrate a reflection coefficient better than -10 dB and an insertion loss below 0.8 dB over 85.0-96.9 GHz. Under multiple random assembly conditions, the phase imbalance between the two output ports remains within ±1°, confirming the excellent phase robustness and assembly tolerance of the proposed structure.