Antenna device and transformer

A transformer between waveguide and transmission-line, comprising:

• a high-frequency circuit module having differential-pair terminals through which a differential signal is input and output;
• transmission-lines, each being connected to one of the differential-pair terminals;
• a waveguide including a first and second metal walls parallel to each other and one ends of the first and second metal walls are connected each other through a third metal wall;
• and
• feed pins being arranged inside of the waveguide, each being connected to one of the transmission-lines, having a first distance of approximately (λg/2) away from each other, one of the feed pins having a second distance of approximately (λg*(1+2 α)/4) away from the third metal plane, “λg” is a wavelength in the waveguide, and “α” is an integer which is equal or larger than “0”,
• wherein each of the feed pins has a third distance of approximately (a/2) away from the first or second wall, “a” is length of the waveguide along the third metal wall.