Millimeter-wave 3D printing metasurface filtering crossover based on a single groove gap waveguide cavity

• The filtering crossover we developed exhibits lower insertion loss. • Our design achieves a third-order filtering crossover using a single GGWR, resulting in a highly compact structure. • The filtering crossover leverages a precise degenerate mode, ensuring excellent isolation performance. • The independently controllable TZ in both the upper and lower stopbands provide high frequency selectivity. A millimeter-wave (mm-wave) 3D-printing metasurface filtering crossover based on groove gap waveguide (GGW) structure is proposed in this letter. Firstly, the metasurface composed of elec­tromagnetic bandgap elements in GGW technology is designed and analyzed. This configuration effectively mitigates radiation and electromagnetic wave leakage. The upper part of the GGW resonator features a groove structure with periodic pins distributed, while the lower part consists of a metal groove structure. Subsequently, by incorporating resonant irises, the device order and bandwidth are increased. Transmission zeros (TZ) is generated by cross-coupling between the GGW resonator and source. Furthermore, by adding an L -shaped capacitive stub at one end of each port, another TZ is created, further enhancing the frequency selectivity of the filtering crossover. To verify the design, a third-order filtering crossover operating in the Ka band is fabricated using 3D printing technology. The measured results show excellent agreement with the simulations. The final filtering crossover achieves a 3-dB fractional bandwidth of 4.8 %, a return loss better than 19.5 dB, and an in-band isolation greater than 32 dB.