INVESTIGATION ON METMAMTERIAL BASED HIGH POWER MICROWAVE DEVICES

Abstract

High-power microwave (HPM) devices are advanced vacuum electron devices known for their exceptional efficiency and energy output. These devices have diverse applica tions across numerous sectors, including military and defense, communications, high energy research, industrial processes, and healthcare. In the advancement of HPM de vices, the assistance of metamaterial (MTM) structure significantly improved the device performance by increasing their efficiency and power generation. The MTM-loaded inter action structures are compact in size, highly resonant, and provide a dispersive negative refractive medium for wave propagation. Therefore, the MTM-inspired vacuum electron devices (VEDs) are designed and investigated for traveling wave tubes (TWTs) and back ward wave (BW) oscillators (BWOs) applications. In this dissertation, metallic MTM loaded slow-wave structures (SWSs) are designed for high efficiency and HPM genera tion. Moreover, the double-negative MTM (DNM)-assisted helical SWS is investigated using theoretical and simulation approaches for VED applications. An MTM-loaded all-metallic SWS is designed. The structure consists of periodically arranged split-ring resonator (SRR) pairs within a cylindrical guide, with azimuthal repe tition at every 120◦. The frequency range of 1.85-2.60GHz defined the DNM regime for the designed structure. The structure exhibits MTM properties such as negative refrac tive index, extremely small and negative group velocity, below-cutoff BW propagation, among others. The hot-test simulation analysis of the MTM-SWS determined the power generation of 140MW at the operating frequency of 2.1GHz within the pulse duration of 18-20ns. Furthermore, the structure demonstrates an efficiency of 41% during this operational phase. A novel multibeam MTM-BWO is designed using a four-beam all-metallic MTM SWS comprising several broadside-coupled SRR (BC-SRR) pairs, arranged periodically in axial direction and repeated azimuthally. This MTM-BWO is investigated with the ob jectives of DNMoptimization, dispersion and interaction characterization, and S-parameter validation. The designed multibeam MTM-BWO oscillates at 2.17GHz operating fre quency and radiates TE21-like electromagnetic (EM) waves. It generates an average out put power of 175MW within 22-24ns with an efficiency of 43%.