Patent ID: 8207797

Claim:
A balun, comprising: a first substrate, comprising a first surface and a second surface, wherein the first surface is opposite to the second surface; a feed conductor, comprising a feed portion and an extended feed portion, wherein the feed conductor is disposed on the first surface extending along a first axis; a second substrate, comprising a third surface and a fourth surface, wherein the third surface faces the second surface; a first ground layer, disposed on the third surface corresponding to the feed portion; a second ground layer, disposed on the third surface corresponding to the extended feed portion, wherein a gap is formed between the first ground layer and the second ground layer; and a common ground element, disposed on the fourth surface, wherein the common ground element is electrically connected to the first ground layer and the second ground layer, the common ground element comprises a first common ground portion, and the first common ground portion is parallel to the first axis and corresponding to the feed conductor, wherein the first ground layer comprises a first output port, the second ground layer comprises a second output port, the first output port and the second output port are located on a second axis and extend toward opposite directions, and the second axis is perpendicular to the first axis.