Application of Metamaterials in Microwave Resonators and Slow Wave Structures

Although potential application of metamaterials in various areas of optics and electromagnetics has been investigated to a great extent in the recent years, interaction of free electrons with metamaterials or more precisely metamaterial loaded slow wave structures (SWSs) which may result in vacuum devices with superior performance is one of the areas that has not been extensively considered in the literature.
In this thesis, the SWS of a specific type of vacuum electronic devices called spatial harmonic magnetron (SHM) has been considered, then by developing a novel approximate theory it has been shown that loading the SWS of a SHM with an epsilon near zero metamaterial can enhance beam wave interaction and as a consequence improve the output power and efficiency of this device. Details of the realization of the metamaterial loaded SWS has been presented and a 41 GHz metamaterial loaded SHM has been designed. By developing an accurate simulation model in CST-Particle Studio, the hot cathode performance of the metamaterial loaded SHM has been compared with that of its conventional counterpart at 41 GHz.
Before involving in the complexity of the beam wave interaction in a metamaterial loaded SWS, metamaterial loaded cylindrical and coaxial cylindrical resonators have been investigated in this thesis. These investigations revealed interesting miniaturization possibilities for both TE and TM mode cylindrical resonators and, on the other hand, provide the preliminary tools and steps for analyzing the metamaterial loaded SWS. Presenting the dispersion relations of the metamaterial loaded resonators in a generally anisotropic case has revealed the possibility of employing less complex anisotropic metamaterials instead of their complex isotropic counterparts in order to realize miniaturized resonators.