Patent ID: 8441405

Claim:
A transformer between a waveguide and a transmission-line, comprising: a high-frequency circuit module having differential-pair terminals through which a differential signal is output; transmission-lines, each being connected to one of the differential-pair terminals; a waveguide including first and second metal walls parallel to each other and ends of the first and second metal walls are connected to each other through a third metal wall; and feed pins being arranged inside of the waveguide, each feed pin being directly connected to a respective 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+2α)/4) away from the third metal wall, “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, and wherein the differential signals are output from the high-frequency circuit module into the waveguide through the feed pins being directly connected to the transmission-lines.