Patent ID: 7271686

Claim:
A dielectric filter comprising: a planar-shaped lower conductor and a planar-shaped upper conductor; a dielectric substrate which includes a plurality of dielectric layers stacked therein and is interposed between the lower conductor and the upper conductor being in contact therewith; an interior conductor layer having a plurality of resonance aperture areas that is provided in at least one of the dielectric layers inside the dielectric substrate; and a multilayer-type waveguide formed by lines of via conductors arranged inside the dielectric substrate, wherein the resonance aperture areas are juxtaposed with a predetermined distance in between, an open end portion of the multilayer-type waveguide is opposed to one of the plurality of resonance aperture areas provided in the interior conductor layer, and wherein a distance between the lines of via conductors increases to form a funnel or horn shape as the location thereof nears the resonance aperture areas, and one of the dielectric layers has a larger thickness than any of the other dielectric layers, said plurality of dielectric layers disposed; (1) between the upper conductor and the interior conductor layer, and (2) between the interior conductor layer and the lower conductor; said dielectric layer of larger thickness having a cutoff frequency fc that is higher than a frequency f used, and at least one or both of signal input and signal output is effected by the multilayer-type waveguide.