The modelling and simulation of 2:1 balance-to-unbalance transmission-
line transformers (balun TLT) are presented. The validity of the compl
ete equivalent model of the basic 2:1 balun is confirmed by the excell
ent match between the simulated results and experimental data. This co
mplete model makes a contribution to predict and explain the character
istics of the 2:1 balun, including low-frequency and high frequency op
eration.