【作者】 张雍；

【导师】 杨建红；

【作者基本信息】 兰州大学 ， 微电子学与固体电子学， 2010， 博士

【摘要】 螺旋线慢波结构是最重要的宽频带高增益行波管慢波系统,良好的色散特性、低的相速度、高的耦合阻抗、简单的制造工艺,使其广泛应用于通信系统、现代雷达和电子对抗等军事领域。螺旋线慢波结构的慢波特性研究对提升行波管的工作带宽与增益有重要意义；而它的选频及贮能特性研究是铷原子频标星载小型化所需考虑的重要方面。本博士学位论文围绕螺旋线慢波结构的理论分析与应用设计展开研究工作,详细分析了螺旋线慢波结构以及它的变型：加载介质夹持杆和金属翼的螺旋线慢波结构。从分析电磁慢波系统开始,以螺旋导电面理论为基础,采用场匹配方法,建立了单螺旋绕线慢波结构理论模型、加载圆柱形和矩形夹持杆螺旋线慢波结构理论模型、加载扇形金属翼与T型金属翼螺旋线慢波结构理论模型。利用VBA自编程序处理计算数据。根据CST MWS软件建模结果,在实验结果验证的基础上,对色散特性和耦合阻抗特性进行了比对分析,总结出各项结构参量对慢波特性的具体影响,为行波管的慢波结构设计提供参考。同时,在此基础上,详细分析了螺旋线慢波结构在铷原子频标中的电磁波传播特性,研究螺距和介质材料对特性的影响程度,从而对现有结构进行改进性设计,实现了铷原子频标星载小型化之目的。主要工作和结论如下：(1)以电磁慢波系统为基础,建立单螺旋绕线慢波结构的螺旋线导电面模型。同时以有限积分理论为基础,利用数值模拟方法,对单螺旋绕线慢波结构进行建模设计。结合理论模型和建模结果,首次呈现该结构的电磁场分布状态,为将螺旋线慢波结构应用到铷原子频标中提供理论基础。(2)针对加载介质夹持杆螺旋线慢波结构,建立了考虑螺旋带厚度、螺旋带宽度、以及夹持杆形状的螺旋带模型。利用等效介质圆环计算等效介电常数。通过场匹配法得到加载圆柱形和矩形块夹持杆慢波系统的色散关系和耦合阻抗。比对不同管壳半径、夹持杆材料、几何形状、螺旋带厚度和宽度对系统慢波特性的具体影响,提出了优化结构参量之方法,为含有夹持杆的螺旋线慢波结构设计提供指导。(3)针对加载金属翼螺旋线慢波结构,提出采用傅里叶空间转换方法,将金属翼片所在区域转换为傅氏空间,建立电磁场方程,求解系统色散关系和耦合阻抗。利用此种方法使分析加载金属翼片螺旋线慢波结构的理论模型计算精度得到提高,相比有限厚度翼片螺旋导电面模型,其精度提高了一倍。在此基础上分析了加载扇形翼片与T型翼片系统的慢波特性,得出对于相同结构参数的两种翼片慢波系统,加载T型金属翼的螺旋线慢波结构特性优于加载扇形金属翼；同时首次提出通过调节翼片参数可以使得系统呈现出正性或负性的色散关系,为应用在超高频带宽的螺旋线慢波结构设计提供指导。(4)在利用CST MWS模拟圆柱型谐振腔体的基础上,研究了应用在铷原子频标中TE111腔体的电磁场分布状态,得到了腔体品质因数和设计参数,设计了加载介质的TE111模谐振腔体,使腔体体积得以压缩,为铷原子频标星载小型化提供设计思路。(5)以螺旋线导电面模型为基础,首次分析了应用在铷原子频标中的螺旋线慢波结构腔体的电磁场方程,求解了色散关系和耦合阻抗,比对了不同螺距和介电常数对慢波特性的影响。同时沿着在腔体中添加介质层用以压缩体积的思路,设计出改进型螺旋线慢波结构腔体。利用更小的螺距及恰当的介质使得腔体体积进一步压缩。利用温控电路用以减小改进型螺旋线慢波腔体的腔牵引效应。通过将该腔体应用于铷原子频标中,获得其腔体谐振吸收线、铷原子频标的频率稳定度,信噪比,及温度稳定度,这些关键参量能够达到星载铷原子频标小型化设计要求。更多还原

【Abstract】 Helix slow wave structure (helix SWS)is the most important slow wave system of the traveling wave tube (TWT). The good dispersion relationship, low phase velocity, high interaction impedance, and easy manufacture make the helix SWS widely used in modern military, including communication system, modern radar, electronic warfares and, etc. The investigations of the slow wave characteristics, frequency selective and storing energy characteristic are very useful for improving the performance of TWT and miniaturizing Rubidium Atomic Frequency Standards (RAFS).In this doctoral dissertation, the theoretical analysis and application design of the helix SWS have been investigated. We research on the performance of the helix SWS and its modified structures such as with loaded on the dielectric cylindrical or rectangular sup-port rods and sector shaped or T-shaped metallic vanes. Studying on the electromagnetic slow-wave system and field-match theory, we build up some theoretical models based on the spiral conducting surface. Using VBA program to process data and CST MWS mod-eling, the simulated results, including phase velocity, on-axis interaction impedance, and distribution of the electromagnetic field, are implemented and compared with the experi-mented results. The effect of the structure’s parameters on the slow-wave characteristics are analyzed in detail and it can be referenced to the design of the helix SWS in TWT. At the same time, an improved helix SWS based on good propagation characteristics as a resonator for RAFS is designed. The effects of the different helical pitch and dielectric material in the insulator cylinder on the slow-wave characteristics are analyzed in detail. The main tasks and several valuable results are listed as following:(1) Based on the electromagnetic slow-wave system, a spiral conducting surface modeling of the single helix SWS is designed. The theoretical analysis is performed together with the simulations of the propagation characteristics. The distributions of elec-tromagnetic field are presented at the first time. Those conclusions can be the theoretical basis of the applying the helix SWS for RAFS.(2) For analysis of the dielectric support rods-loaded helix SWS, a helical tape model is built up by considering the width or thickness of the helix and the rods’shapes. The dielectric constant is calculated by the equivalent dielectric annulus. The dispersion re-lationship and interaction impedance of loading the cylindrical or rectangular dielectric support rods are gained by field-matched method. Considering the detailed effects of the helix width and thickness, several ways of optimizing structural parameters are proposed for improving the performance of the helix SWS.(3) The effects of different metallic vane-loaded helix SWS of TWT are proposed based on the analysis of Fourier expansions in the exterior region with metallic vanes. The influences of the metallic vanes dimensions on the phase velocity and interaction impedance are considered in detail. The computed data is compared with the reference data in the practical frequency range with a good consistency. The analytical results reveal that the method of using Fourier expansions can contribute effectively to the reducing of the error between the theoretical and experimented data. By analyzing the computed re-sults, the performances of the helix SWS, with T-shaped metallic vanes are superior to the sector-shaped with the same designed parameters. Adjustments can be made to the outer radius of T-shaped metallic vanes which then control the dispersion relationship showing either negative or positive, and it is similar to sector-shaped vanes by adjusting its inner radius. It is useful to design the helix SWS worked in the ultra high broadband.(4) Based on the simulation of the cylindrical resonator in RAFS using CST MWS models, the distribution of the electromagnetic field and the quality factor Q of TE111 mode are proposed. From analyzing the parameters, we design a miniaturized cavity with loaded the dielectric materials to compact the volume of RAFS. It is helpful to design a more smaller RAFS.(5) Based on the helix conducting surface model, the electromagnetic field equations of the helix SWS as the resonator cavity for RAFS is solved at the first time. An im-proved helix SWS based on good propagation characteristics as a helical resonator for RAFS is designed. The theoretical analysis is performed together with the simulations of the propagation characteristics. The simulated results, including phase velocity, on-axis interaction impedance, and distribution of the magnetic field, are implemented and compared with the experimented results. The effects of the different helical pitch and di-electric material in the insulator cylinder on the propagation characteristics are analyzing in detail. The analyzed results show that smaller helical pitch and proper usage of dielec-tric material in the insulator cylinder can make the propagation characteristics of the helix SWS superior. Then a heating circuit of temperature stability is designed to weaken the cavity-pulling effect. The improved helix SWS have been applied in RAFS and the rela-tion parameters, including the resonant cavity’s resonance line, frequency stability, SNR, and temperature stability are all achieved.更多还原