Model for the low-frequency performance of ferrite-loaded balun transformers

This paper presents a model for the low- frequency response of the ferrite-loaded transmission-line transformer. The ferrite is characterized by measured impedance and the performance of the transformer is determined through basic circuit-analysis techniques. The validity of the model is established by measurements on a 50-Ω balun with various groundings of the load. Input impedance, SWR, gains, and phases are predicted accurately at frequencies up to several hundred megahertz.