Patent ID: 7633353

Claim:
A balun circuit disposed between a first terminal, a second terminal, and a third terminal, comprising: a first coupling line in which an unbalanced line thereof is connected to the first terminal and a balanced line thereof is electrically connected to the second terminal; a second coupling line having characteristics identical to those of the first coupling line in which an unbalanced line thereof is electrically connected to the unbalanced line of the first coupling line and a balanced line thereof is electrically connected to the third terminal; a first transmission path that is serially connected between the balanced line of the first coupling line and a ground potential and extends in a direction away from the balanced line of the first coupling line; a second transmission path that is serially connected between the balanced line of the second coupling line and a ground potential and extends in a direction away from the balanced line of the second coupling line, the length of the second transmission path being different from the length of the first transmission path; and a third transmission path that is serially connected between the unbalanced line of the first coupling line and the unbalanced line of the second coupling line, wherein the first transmission path, the second transmission path, and the third transmission path are formed in a manner and the lengths of the first transmission path and the second transmission path are adjusted in a manner such that an amplitude characteristic from among signal passing characteristics from the first terminal to the second terminal is the same as an amplitude characteristic of signal passing characteristics from the first terminal to the third terminal and such that a phase characteristic from among the signal passing characteristics from the first terminal to the second terminal is a characteristic having an inverted phase in relation to a phase characteristic of the signal passing characteristics from the first terminal to the third terminal.