Patent ID: 7239221

Claim:
A dual mode band-pass filter comprising: a dielectric substrate having first and second main surfaces; a metallic film having an opening and disposed on the first main surface of the dielectric substrate or inside of the dielectric substrate; at least one ground electrode disposed on the second main surface of the dielectric substrate or inside of the dielectric substrate, so as to be opposed to the metallic film with the dielectric substrate disposed therebetween; and a pair of input-output coupling circuits connected to different portions of the metallic film; wherein the metallic film has one of a substantially rhomboid shape and a substantial triangular shape; and the metallic film and the opening therein are configured such that first and second resonance modes of the dual mode band-pass filter are coupled; the metallic film includes at least a first vertex, a second vertex, and a third vertex; the first vertex and the second vertex are disposed at end portions of a first straight side of the metallic film; the first vertex and the third vertex are disposed at end portions of a second straight side of the metallic film; one of the different portions to which one of the pair of input-output coupling circuits is connected is located between the first vertex and the second vertex of the metallic film; the other of the different portions to which the other of the pair of input-output coupling circuits is connected is located between the first vertex and the third vertex of the metallic film; a length of a first portion of the first straight side between the first vertex and the one of the different portions to which one of the pair of input-output coupling circuits is connected and a length of a second portion of the first straight side between the second vertex and the one of the different portions to which the one of the pair of input-output coupling circuits is connected are different from each other; and a length of a third portion of the second straight side between the first vertex and the other of the different portions to which the other of the pair of input-output coupling circuits is connected and a length of a fourth portion of the second straight side between the third vertex and the other of the different portions to which the other of the pair of input-output coupling circuits is connected are different from each other.