A novel topology of broad-band coaxial impedance transformer

Broad-band low-loss transmission-line transformers are key components in the design of RF high-power transmitters. In this work systematic analysis of ferrite-based coaxial transformers is presented, in order to clarify trade-offs inherent both to the ideal structures and to the ferrite and mounting parasitics. A novel topology of 1:4 impedance transformer is presented, based on inductive compensation of the ferrite parasitic capacitance. Design and measurements of a 400 W 1:4 transformer in the band 20-500 MHz have been carried out to demonstrate performance of the proposed topology.