A novel model for a planar wideband Marchand balun

A new lumped element model for conventional Marchand baluns is presented. Analyzed by the even- and odd-mode method, the equivalent equations are derived for λ/4 coupled lines. Based on the proposed 5th-order lumped equivalent circuit for λ/4 coupled lines, the self-inductance, mutual inductive coupling and the capacitance can be calculated according to the even- and odd-mode characteristic impedance, therefore, the model parameters of the balun can be easily gained from the derived equations. To verify the model, a GaAs monolithic wideband Marchand balun was implemented and tested. The EM simulation and experimental results show a good agreement with the model simulation. This model is available in a wide frequency range and makes the design procedure of the Marchand balun faster and easier. (semiconductor integrated circuits)