Patent ID: 7924112

Claim:
A balun, comprising: a first metallic layer, having a first conductive pattern; a second metallic layer, comprising: a first spiral line, comprising an unbalanced I/O end and a first connection end; and a second spiral line, comprising a second connection end and an open-circuit end; a third metallic layer, comprising: a third spiral line, corresponding to the first spiral line and comprising a third connection end electrically connected to the first conductive pattern, and a first balanced I/O end; and a fourth spiral line, corresponding to the second spiral line and comprising a fourth connection end electrically connected to the first conductive pattern, and a second balanced I/O end; a first dielectric layer, disposed between the second metallic layer and the third metallic layer; a fourth metallic layer, via which the first connection end is electrically connected to the second connection end; a second dielectric layer, disposed between the third metallic layer and the fourth metallic layer; and a dielectric substrate, having a first surface and a second surface opposite one to another, wherein the first metallic layer is disposed on the first surface by thin film processing, and the second metallic layer, the third metallic layer, the first dielectric layer, the fourth metallic layer and the second dielectric layer are disposed on the second surface by thin film processing.