3-line balun transformer

PURPOSE: A three-line balun transformer is provided to simplify the configuration of the transformer by reducing the number of ground ports, while allowing for ease of manufacture. CONSTITUTION: A three-line balun transformer(50) comprises an unbalanced port(54) for inputting or outputting an unbalanced signal; a first balanced port(55) and a second balanced port(56) which have the same size, and output or input balanced signals having a phase difference of 180 degrees; a first line(51) having a first end connected to the unbalanced port and a second end to be grounded; a second line(52) spaced apart from the first line and arranged in parallel with the first line, wherein the second line has a first end and a second end which is connected to the first balanced port; and a third line(53) spaced apart from the second line and arranged in parallel with the second line, wherein the third line has a first end connected to the first end of the second line and a second end connected to the second balanced port.