Balun Design

Balun DesignSheet 1 of 6

Balun Design In the design of mixers, push-pull amplifiers, baluns are used to link a symmetrical (balanced) circuit to a asymmetrical (unbalanced) circuit. Baluns are designed to have a precise 180-degree phase shift, with minimum loss and equal balanced impedances. In power amplifiers loss of symmetry will degrade efficiency and the symmetrical port must be well isolated from ground to eliminate parasitic oscillations. The basic construction/design of a balun consists of two 90-degree phasing lines that provide the required 180-degree split, and this involves the use of λ/4 and λ/2. A wire-wound transformer provides an excellent balun. Miniature wirewound transformers are commercially available covering frequencies from low kHz to beyond 2GHz. They are often realised with a