A balun, short for balanced-unbalanced, is a passive electronic device used to convert between balanced and unbalanced signals in RF and microwave systems. It transforms signals between a balanced transmission line (e.g., twisted pair, coaxial cable) and an unbalanced transmission line (e.g., coaxial cable). Baluns are commonly used in antenna systems, RF transceivers, and RF circuits to match impedance, reduce signal distortion, and minimize common-mode noise.