Patent ID: 7151421

Claim:
A coupler comprising: a first dielectric substrate having a first surface and a second surface which are parallel to each other; a second dielectric substrate having a first surface and a second surface which are parallel to each other, said second dielectric substrate being placed on said second surface of said first dielectric substrate; a third dielectric substrate having a first surface and a second surface which are parallel to each other, said third dielectric substrate being placed on said second surface of said second dielectric substrate; a ground conductor on said first surface of said first dielectric substrate; two coupling line conductors each having a length of a ¼ wavelength, said coupling line conductors being close to each other on said second surface of said second dielectric substrate so as to be electromagnetically coupled to each other; plural via conductors filled in plural through holes passing through said second dielectric substrate or said third dielectric substrate, and placed and connected to said two coupling line conductors; and via conductors filled in through holes passing from said first dielectric substrate to said third dielectric substrate, and said via conductors in said through holes passing through said three substrates are arranged to make opposing ends of said two coupling line conductors short-circuit to said ground conductor on each of said first dielectric substrate, thereby providing comb-line coupling.