Patent ID: 7868718

Claim:
A balanced filter device, comprising: an unbalanced-side resonance electrode coupled to an unbalanced terminal; a first pair of resonance electrodes directly connected to a pair of balanced terminals, and at least one second pair of resonance electrodes, wherein said unbalanced side resonance electrode, said first pair of resonance electrodes and said at least one second pair of resonance electrodes are formed on different dielectric layers in a laminated arrangement, wherein the at least one second pair of resonance electrodes is interposed between said unbalanced-side resonance electrode and said first pair of resonance electrodes, wherein the device further comprises a coupling electrode interposed between said at least one second pair of resonance electrodes and said unbalanced-side resonance electrode, wherein said unbalanced-side resonance electrode comprises a λ/2 strip-line folded into two substantially equal λ/4 strip-line portions, and wherein said coupling electrode couples the folding point of the λ/2 strip-line to at least one point on each of the two λ/4 strip-line portions.