A marchand balun with a reduced plane size is disclosed. The marchand balun provides two coupling units each having two transmission lines coupled to each other and having a length of λ/8, where λ is a characteristic wavelength of a signal subject to the marchand balun. The marchand balun further provides an additional unit, where two coupling unit and the additional unit are connected in series to each other. The additional unit is one of a transmission line with a length of λ/16 with one open end and a capacitor with one grounded end.
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