Simulation Study On Electromagnetic Properties Of Coaxial Bragg Resonator

Both Cyclotron Auto-resonance Maser (CARM) and Free Electron Laser (FEL) as high efficiency, high power microwave (HPM) sources have a vast application prospect in many areas such as radar, electronic countermeasures, microwave directed energy weapon, plasma heating, controlled thermonuclear reaction, high-energy accelerator, communication. Among them, Bragg structures have been paid much attention in international in recent years as high frequency beam-wave interaction resonator in Cyclotron Auto-resonance Maser (CARM) and Free Electron Laser (FEL) oscillator.Bragg structure is usually a kind of periodic structure with continuous corrugation phase, which has excellent mode selectivity and frequency selectivity properties. When phase jump is introduced to Bragg structure, the corrugation phase continuity is destroyed, which can provide some unique properties.In previous works, extensive theoretical and experimental studies have been devoted to the planar or cylindrical Bragg structure, which were mainly confined to the single-mode approximation and the low-order mode, there are more inadequate. In fact, for large dimensional size Bragg structure operated at high frequency especially Terahertz frequency range, the device will inevitably work at the over-moded state, and most operating mode is higher-order mode. Investigations of the rectangular ripples Bragg structures with phase jump are also mainly concentrated on the cylindrical and coaxial Bragg structure.However, in some practical applications, they require for Bragg structure with deeply corrugated ripples, or demand for working at TM mode, or need to make use of corrugation phase jump properties of coaxial Bragg structures, but the issues were studied insufficiently. Therefore, further study on electromagnetic properties of high frequency higher-order overmoded Bragg structures has academic significance and practical value.In consideration of the existing questions above, nonlinear simulation study on related problems is carried out by making use of three-dimensional electromagnetic simulation software CST in this dissertation, in order to be applied in new type Cyclotron Auto-resonance Maser (CARM) and Free Electron Laser (FEL) oscillator.The main contents of master dissertation are organized as follows:band-gaps properties of high frequency higher-order Transverse Magnetic (TM) over-moded coaxial Bragg reflector are studied, to explore approaches of band-gap-overlap separation and residual-side-lobe elimination, to improve performance of coaxial Bragg reflector; when inner-rod and outer-conductor are deeply corrugated, we explore its influence on frequency response, bandwidth of 3 dB and center-frequency shift of low and high frequency higher-order Transverse Electric (TE) over-moded coaxial Bragg reflector; comprehensive comparative study of four kinds of high frequency higher-order over-moded coaxial resonator electromagnetic characteristics are carried out.