Constant impedance tunable IOT power extraction circuit

The resonant circuit in an Inductive Output Tube (IOT) extracts the kinetic energy of the modulated electron beam converting it to electromagnetic energy. For the application considered here, mobile low-frequency sources (5-10 MHz) for ionospheric heating, high efficiency is important, and thus class D operation is desired. The broad frequency range requires the circuit to be tunable, and the need for a constant decelerating voltage requires constant impedance. This paper discusses the design and construction of a resonant circuit with a highly coupled transformer that has the above features. The design and optimization of the circuit was performed with Orcad Spice and the transformer design was designed using Autodesk Inventor and a finite element electromagnetic field solver, Maxwell 3D and HFSS Simulator software.