Waveguide/transmission line converter configured to feed a plurality of antenna elements in an antenna device

A waveguide/transmission line converter configured to convert power transmitted by a waveguide and power transmitted by at least one transmission line to each other, the waveguide/transmission line converter comprising:

• the waveguide having two wide walls and two narrow walls;
• a dielectric substrate arranged in a manner blocking an opening of the waveguide;
• a short-circuit metal layer arranged on a surface of the dielectric substrate and outside of the waveguide, and held at a potential which is the same as a potential of the waveguide either by a metal member penetrating the dielectric substrate along cross-sections of the two wide walls of the waveguide and not along cross-sections of the two narrow walls of the waveguide or by a metal member penetrating the dielectric substrate along the cross-sections of the two wide walls and a cross-section of one of the two narrow walls of the waveguide and not along a cross-section of the other of the two narrow walls of the waveguide;
• and
• a matching element arranged on a surface of the dielectric substrate and inside the waveguide, coupled to the transmission line, and having a resonant length in an electric field direction inside the waveguide and in a feed power direction of the transmission line, wherein the resonant length is adapted to set up, as a standing wave, an electromagnetic wave transmitting the power transmitted by the waveguide and having an effective wavelength in a surrounding environment of the dielectric substrate.