The present disclosure is directed to a balun circuit adapted to operate at a frequency of between about 5 GHz to about 110 GHz. The balun circuit includes first and second output striplines and an input stripline formed on a first surface of the substrate, and a slotline formed on a second surface of the substrate opposite the first surface. The slotline has first and second ends, the first end overlapping the first output stripline and the second end overlapping the second output stripline, and the input stripline overlapping the slotline midway between the first end and the second end.