Patent ID: 7541887

Claim:
A balun, comprising: a first transforming part, comprising: a first coupled line, comprising a first end and a second end; a first transmission line, connected to the first end, comprising a first balanced port; a second transmission line, connected to the second end, comprising a second balanced port; and a first capacitor, for connecting the first balanced port and the second balanced port; and a second transforming part, comprising: a second coupled line, comprising a third end and a fourth end; a third transmission line, connected to the third end, comprising an unbalanced port; a fourth transmission line, connected to the fourth end, an extending end of the fourth transmission line spaced from that of the third transmission line; a first line node, disposed between the extending ends of the third transmission line and the fourth transmission line; a second capacitor, for connecting the third transmission line and the first line node; a second line node, disposed between the extending ends of the third transmission line and the fourth transmission line and spaced from the first line node; and a third capacitor, for connecting the fourth transmission line and the second line node.