Hybrid folded rectangular waveguide filter

A group of rectangular waveguide resonators for use in a rectangular waveguide filter, the group comprising a first resonator and a second resonator,

• wherein the first and second resonators are arranged so that first lateral walls of the first resonator extend in parallel to second lateral walls of the second resonator, the first lateral walls corresponding to broad sides of a first cross section of the first resonator perpendicular to a guide direction of the first resonator and the second lateral walls corresponding to broad sides of a second cross section of the second resonator perpendicular to a guide direction of the second resonator;
• the first and second resonators are further arranged so that one of the first lateral walls at least partially faces one of the second lateral walls and
• the first resonator is electromagnetically coupled to the second resonator through a first aperture in the one of the first lateral walls and a second aperture in the one of the second lateral walls.