【作者】 陈晓辉；

【导师】 张世昌；

【作者基本信息】 西南交通大学 ， 通信与信息系统， 2008， 硕士

【摘要】 高功率毫米亚毫米波源,在雷达、等离子体加热、高能加速器、通信等方面,有着重要的应用前景,一直以来受到各国的重视。而高功率毫米波器件是高功率微波技术的一个重要方向,布喇格反射器(Bragg reflector)是其中的一个重要分支,是目前国内外研究的热点。布喇格结构是一种一维光子晶体被广泛的应用于回旋自谐振脉塞(Cyclotron Autoresonance Maser,CARM),自由电子激光和微波领域。由于在高功率微波领域,它不仅可以提供很好的单模选择性,而且不影响相对论电子注的通过,因此被认为是最适合应用于毫米波、亚毫米波的微波器件。其中,近年来发展起来的同轴布喇格反射器(coaxial Bragg reflector)被公认优于普通的圆柱或者平面型布喇格反射器,受到专家学者的重视。本硕士学位论文利用数值模拟和软件仿真对同轴布喇格反射器进行了比较深入、全面的研究,取得了有价值的研究成果。首先研究了内外导体波纹槽相位差和槽深对同轴布喇格反射器性能的影响。我们分别运用了两种分析方法:一种是根据同轴布喇格反射器腔体内的电磁耦合方程编写仿真程序,来模拟反射器的性能;一种就是利用三维电磁仿真软件对反射器进行全面的仿真测试。为了改善布喇格反射器的性能,消除频率响应曲线的残余旁瓣,我们根据滤波器的原理,对布喇格反射器的波纹进行窗函数加权,分析了渐变同轴布喇格反射器的性能。结果显示,布喇格反射器的性能得到了明显提高,达到了我们预期的目标。在工程实施中,器件的安装调试不可能达到理想的要求,特别是同轴器件,偏心问题非常普遍,因此论文深入分析了同轴布喇格反射器内导体偏心的两种情况对反射器性能的影响,找出最优的解决方案,为工程提供有益的参考。本论文对同轴布拉格反射器的研究,其主要创新点是:1.利用三维电磁仿真软件CST研究了开余弦槽的同轴布喇格反射器内外波纹相位差和开槽深度对反射器的影响,得出当相位差为π时可获得反射系数接近1的最佳效果。2.用窗函数可以有效抑制同轴布喇格反射器的残余旁瓣,比较分析了加不同窗函数对同轴布喇格反射器性能的影响。3.首次考虑工程上的需要,研究了同轴布喇格反射器两种内导体偏心对反射器工作性能的影响,得出在内外波纹槽相位差等于π时,平行偏心和倾斜偏心都对同轴布喇格反射器的传输系数有很小的影响,甚至可以忽略不计,为工程实践提供了有益参考。更多还原

【Abstract】 High-power radiation sources in millimeter and sub-millimeter waves have a great prospect of applications to radar, plasma heating, high-gradient linear colliders, and communications, and therefore, attract more and more attention in many countries. Microwave devices play an important role in high-power microwave technology. And as one of microwave devices, Bragg reflector is focused by researchers in the world.In the past years, Bragg structures have been widely applied as Electromagnetic Band-Gap periodic structures in cyclotron auto-resonance maser (CARM), free electron laser (FEL), and microwave field. Generally speaking, a Bragg reflector is regarded as the most suitable cavity structure in millimeter and sub-millimeter, because it can provide good mode selectivity and high quality factor for the selected mode.This dissertation designs a novel coaxial Bragg reflector, where both the outer wall and inner rod are corrugated with weak sinusoidal ripple, and makes the comprehensive study including numerical and software simulations. Several valuable academic achievements are obtained.Firstly, special simulations are done. Simulation results are compared with two ways. One way is that the reflection characteristics of the coaxial Bragg reflector are evaluated with the code we design according the coupled mode equations introduced in Chapter 2. Another is making use of CST software to analyze the characteristics. Compared to the first way, CST can provide us more comprehensive simulated results. The special simulation indicates that the corrugation phase and amplitude substantially affected the characteristics of the coaxial Bragg reflector.To optimize the characteristics, improved Bragg reflector with window distribution of the slot depth is present, based on a common technique in filter theory. The results in Chapter 5 show that the smooth of pass-band is improved effectively and the anticipative goal is achieved.Finally, two kinds of eccentricity between the outer-wall and inner-rod axes with the coaxial Bragg structure are studied in Chapter 6, because the two eccentricities always happen in practice. The results we obtain can offer the engineering references for the coaxial Bragg reflector.Main innovation points in the dissertation are as follows:1. The influence of corrugation phase and ripple depth on the bandwidth of coaxial Bragg reflector is studied by making use of the CST software. Specific simulation indicates the reflectivity of operating mode is close to 1 with a phase difference ofπ..2. The smoothness of pass band is well improved by introducing window techniques. The situations of Hamming window, Blackman window, Gauss window are studied employing CST.3. The effects of eccentricity between the outer-wall and inner-rod axes on the transmission band gap in a coaxial Bragg structure are analyzed. The influence of the eccentricity is minimized and becomes negligible when the phase difference is equal toπ.更多还原