3rd order coupled-resonator bandpass filter assisted by Groove Gap-Waveguide technology for 26-GHz radio link diplexer

This paper investigates the design of a bandpass filter (BPF) intended for 26-GHz radio-link diplexer using Groove-Gap-Waveguide (GGW) technology. Its unit-cells consist of a rectangular metal-pin which is connected to a bottom metal plate and its other side is electromagnetically coupled to a top plate with an air-gap of approximately λ/4 that creates a bandgap, preventing unwanted electromagnetic-wave propagation. An array of these unit-cells forms a cavity resonator, allowing wave propagation over a specific conductive region. To achieve the desired passband response, a rectangular slot-channel is milled on the bottom metal plate, perturbing the cavity modes and creating the desired filter characteristics.