Patent ID: 7236064

Claim:
A laminated balun transformer including a dielectric block formed by laminating a plurality of dielectric sheets, and a plurality of external electrodes formed on the outer sides of the dielectric block and used for a ground, input/output of the unbalanced signal, input/output of first and second balanced signals, and non-connection, wherein the dielectric block includes: an internal ground electrode formed on a lower layer spaced apart by a certain distance from the top layer of the dielectric block, the internal ground electrode being connected to the external electrode for a ground; a first strip line formed on a lower layer below the internal ground electrode and having one end connected to the external electrode for input/output of the unbalanced signal; a second strip line formed on a lower layer below the internal ground electrode and having one end connected to the other end of the first strip line, the other end of the second strip line being opened; a third strip line formed in parallel with the first strip line on a lower layer below the internal ground electrode and having one end connected to the external electrode for a ground and the other end connected to the external electrode for input/output of the first balanced signal; and a fourth strip line formed in parallel with the second strip line on a lower layer below the internal ground electrode and having one end connected to the external electrode for a ground and the other end connected to the external electrode for input/output of the second balanced signal, wherein the bottom layer of the dielectric block is mounted on a ground pattern of a substrate, the first to fourth strip lines are formed on different layers in the dielectric block, and the dielectric block further includes a non-ground electrode made of a conductive metal material and formed on a layer between the third strip line and the fourth strip line in parallel with each other for forming an electrical shielding between the first and third strip lines and the second and fourth strip lines.