A Novel 3-D Printed G-M-G Integration Method for H-Plane GGW and E-Plane MW Resonators in mm-Wave Wide-Stopband Filter Designs

This article proposes an innovative methodology for designing millimeter-wave groove gap waveguide (GGW) filters with wide stopbands. To overcome the limitations caused by the dense high-order cavity modes and periodic pin modes, a novel and effective GGW-metal waveguide-GGW (G-M-G) integration method is introduced, which embeds an E -plane metal waveguide resonator within back-to-back H -plane GGW resonators. First, a wide-stopband bandpass filter (BPF) is designed by embedding an E -plane TE₁₀₁-rectangular waveguide cavity between two TE₁₀₂-mode GGW cavities. The GGW cavities utilize the TE₂₀₁ mode for resonant decoupling, producing two freely switchable transmission zeros (TZs) flanking the passband. Leveraging the unique H -to- E -plane coupling and high-order mode interleaving between GGW and rectangular waveguide resonators, a −20 dB stopband extending to 2.25 f₀ is realized. Second, the rectangular resonator is replaced with a dual-mode cross-shaped resonator. Its two orthogonal TE₁₀₁-like modes couple with the TE₁₀₂ and TE₂₀₁ modes in the GGW cavities, forming a dual-band BPF with a −20 dB stopband reaching 2.08f₀ . Furthermore, by altering the port arrangement, the dual-band BPF can be converted into a wide-stopband diplexer. Prototypes of both BPFs fabricated using stereolithography (SLA) 3-D printing demonstrate wide stopbands, compact size, and high selectivity. Measured results validate the method’s effectiveness for advanced millimeter-wave wireless communication systems.