Modelling of three-port RF transformers

A new model of a three-port transformer, with a ferrite core is presented. The transformer's operating frequency lies in the VHF and lower UHF range. The presented model is compatible with most common computer programs for network analysis and synthesis. A measurement method is given for model parameter extraction, including a discussion of stray elements and loss mechanisms. Application of the transformer model to a feedback amplifier with two stages, each with a ferrite transformer in its feedback network, proves the validity of the model.