Design of an Oppositely-Oriented Circular Split-Ring Resonator-Loaded Multibeam All-Metallic Metamaterial Backward-Wave Oscillator

In this article, we proposed a novel metamaterial (MTM) inspired interaction structure for high-power microwave backward-wave oscillator (BWO). The proposed structure is an all-metallic MTM slow wave structure (MSWS) which comprises of a number of broadside-coupled split ring resonator (BC-SRR) pairs, arranged periodically in the axial direction and repeated azimuthally. Each pair of oppositely oriented split ring resonator (SRR) provides negative $\mu$ and the cylindrical waveguide generates negative $\varepsilon$ medium for below cutoff TE-modes propagation. The full wave cold simulation analysis of the proposed structure, using computer simulation technique (CST)-microwave studio, has been carried out with the objectives of double-negative medium (DNM) optimization, dispersion, and interaction characterization, and S-parameter validation. For the particle-in-cell (PIC) simulation analysis, the CST-particle studio (CST-PS) has been used. In this work, we report an operation of the proposed MTM-loaded BWO (MTM-BWO) employing a beam potential and total beam current of 340 kV and 1.2 kA, respectively, generating an output power of 175 MW within 22–24 ns with an efficiency of 43% using the four-beam MSWS. As compared to its three-beam counterpart, the four-beam structure generates higher power with better efficiency.