A multibeam metamaterial backward wave oscillator

Abstract

Microwave sources transform the kinetic energy of an electron beam into microwaves through the interaction of electrons with a periodic slow wave structure (SWS). A metamaterial (MTM) waveguide is proposed for use in a microwave oscillator instead of a conventional periodic SWS that has been used for a long time to generate high power microwave radiation. MTMs have interesting properties such as the negative refractive index, low group velocity, and below cutoff propagation, among others. In this work, we study the interaction of a multibeam cathode with a set of MTM structures inside a cylindrical waveguide. We developed a structure comprising a number of MTM metallic plates that have periodicity in the axial direction and are repeated in the azimuthal coordinate. Using eigenmode simulations, we obtained negative dispersion around the operating frequency where the group velocity is negative and extremely small. The fully electromagnetic, relativistic particle-in-cell codes MAGIC and CST Particle Studio and the fully electromagnetic software tool CST Microwave Studio were used to obtain the results in this study.