Waveguide circuit

A waveguide circuit comprising:

• a first waveguide tube having a first cross-sectional shape to allow propagation of a TE mode;
• a second waveguide tube disposed adjacent to the first waveguide tube and having a second cross-sectional shape to allow propagation of a TE mode;
• and
• a third waveguide tube having a tube axis perpendicular to both a tube axis of the first waveguide tube and a tube axis of the second waveguide tube, and having a third cross-sectional shape to allow propagation of a TE mode, wherein,
• the first cross-sectional shape has a pair of straight-line long sides facing each other and a pair of straight-line short sides facing each other, in a plane orthogonal to the tube axis of the first waveguide tube,
• the second cross-sectional shape has a pair of straight-line long sides facing each other and a pair of straight-line short sides facing each other, in a plane orthogonal to the tube axis of the second waveguide tube,
• the first waveguide tube has a pair of sidewalls which form the pair of straight-line short sides of the first cross-sectional shape,
• the second waveguide tube has a pair of sidewalls which form the pair of straight-line short sides of the second cross-sectional shape,
• the pair of straight-line long sides of the second cross-sectional shape is parallel to the pair of straight-line long sides of the first cross-sectional shape,
• the tube axis of the second waveguide tube is parallel to the tube axis of the first waveguide tube,
• one sidewall of the pair of sidewalls of the second waveguide tube is disposed to face one sidewall of the pair of sidewalls of the first waveguide tube, and
• the third waveguide tube includes a coupler which connects a hollow guide of the third waveguide tube to both a hollow guide of the first waveguide tube and a hollow guide of the second waveguide tube.