A compact planar balun formed on a substrate including a hairpin-shaped conductive microstrip and a single-ended contact. The hairpin-shaped conductive microstrip includes first and second linear segments integrally formed with a U-shaped segment, and a single-ended contact is conductively coupled at a location along the first linear segment. The first and second linear segments each have a first characteristic impedance and are in parallel with each other having a first end forming first and second differential contacts and having a second end. The U-shaped segment has a second characteristic impedance that is less than the first characteristic impedance in order to achieve proper scatter parameter alignment. The U-shaped segment may be generally formed thicker or wider than the linear segments to achieve a reduced characteristic impedance. In the alternative or in addition, co-planer ground metal is formed closer to the U-shaped segment to achieve a reduced characteristic impedance.