同轴交错圆盘加载波导慢波结构高频特性的研究

采用多导体传输线分析方法, 对同轴交错圆盘加载波导慢波结构进行了理论分析, 得到了这种慢波结构的色散方程; 利用该色散方程, 得到的色散特性与HFSS仿真软件模拟结果符合良好. 分析了结构参数的变化对同轴交错圆盘加载波导慢波结构的色散特性影响. 结果表明: 增加内径和减小慢波结构的单位周期长度可以拓展慢波结构的带宽. 对同轴圆盘加载波导和同轴交错圆盘加载波导两种慢波结构的色散特性进行了比较, 结果表明: 采用圆盘交错加载方式可以减弱色散, 拓展带宽. 研究结果对同轴交错圆盘加载波导在毫米波行波管中的应用具有指导意义. 关键词： 行波管 同轴交错圆盘加载波导 慢波结构 色散特性     

Backward Wave Oscillators With Coaxial Structures: Dispersion Relation and PIC Simulation

The dispersion relation of a corrugated—wall resonator with an inner coaxial structure has been analyzed as well as the effects of the corrugation period, amplitude and the radius of the coaxial structure on it. Furthermore, we got an output power of 2.1GW at frequency 11.09GHz in a non-uniform slow wave structure by using the PIC simulation software—MAGIC.     

脊加载同轴交错圆盘波导的高频特性

提出脊加载同轴交错圆盘波导慢波结构,并用电磁场仿真软件HFSS对其色散特性和耦合阻抗进行了计算,分析了不同结构参数对其高频特性的影响。研究表明:脊加载同轴交错圆盘波导有较好的色散特性,它比非同轴结构的带宽有明显增加,同时可以降低慢波结构的相速,用作行波管慢波结构时可以降低工作电压。脊加载同轴交错圆盘波导是一种全金属结构,散热性能好,损耗低,在毫米波及亚毫米波段的行波管中有较好的应用前景。     

Study of Rayleigh type surface wave in the initial stressed irregular bottom of ocean due to point source

Rayleigh type surface wave propagation in the irregular bottom of ocean model which is the interface of homogeneous liquid layer over laying an irregular boundary of homogeneous orthotropic half space under initial stresses has been discussed in this paper. Three different dispersion equations are obtained in the form of simple equation using and not using Perturbation technique. Some special cases have been considered. The effect of irregularity, initial stressed, point source, and depth of liquid layer on the propagation of Rayleigh waves has been analyzed and results of numerical discussion have been presented graphically for three different dispersion equations. Mainly the graphs are shown the variation of phase velocity with wave number in different cases.     

Spectral Domain Analysis of Coaxial Cavities

Coaxial cavities are used in high power gyrotrons as the beam-wave interaction structure. Much research has been devoted to their mode selective properties. A coaxial cavity lacks a sharp boundary at its open end, so it has some physical features that can only be observed using a spectral model, such as frequency-dependent field profiles and mode overlapping effects. These properties are important since cold tests are usually conducted in the frequency domain. This study applies the incident/reflected wave boundary condition to the wave equation of a weakly irregular coaxial waveguide. The resistivity of the wall is considered in the analysis. Calculations reveal that the fixed-position spectrum yields an uncertain resonant frequency and quality factor. Although the maximum-field spectrum can uniquely determine the properties of the coaxial cavity, the resonant frequency obtained using the maximum-field spectral model is inconsistent with that obtained using the temporal model. The field-energy spectrum explains the low Q nature of the coaxial cavity. Moreover, resonant frequencies evaluated using the field-energy spectrum agree precisely with those evaluated using the temporal model.     

The Linear Analysis of Coaxial Helical-Groove Slow-Wave Structure

The coaxial helical-groove slow-wave structure is a new-type high power circuit. The dispersion equation of this circuit with an annular electron beam is obtained according to self-consistent field theory. The computation results of the hot dispersion equation show the relations between electron beam parameters and the small signal gain. The presented analysis will be useful for the design of the TWT with coaxial helical-groove circuit.     

有孔矩形腔屏蔽效能的传输线法分析

首先介绍了用传输线法（transmission line method,TLM）分析有孔矩形腔屏蔽效能的基本原理，然后将基本公式作进一步扩展，使其能计算圆孔、多孔洞以及在任意极化方向时的情形。仿真结果表明:当频率低于主谐振频率时，离孔缝越近，耦合进的电磁能量越大；当处于谐振频率时，屏蔽腔与孔形成共振，屏蔽效能很低甚至为负，而且腔体内任何空间都如此；屏蔽效能随极化角度的递增而递减，低频段的屏蔽比高频段要好；对于相同面积的孔洞，单孔洞的屏蔽效能比多孔洞的屏蔽效能要差，孔洞越多，屏蔽效果越好，而圆形孔（等同于方形孔）的屏蔽效果最好。     

同轴慢波结构相对论高功率微波产生器理论分析

 推导了同轴波导的空间电荷限制流,其值大于圆波导的空间电荷限制流。因此在阴极电势和束流相等的情况下,同轴波导中的束流具有更高的动能,同轴器件有可能获得更高的微波转换效率。理论推导出同轴慢波结构中考虑束流空间电荷影响的色散方程,利用Matlab进行了编程求解。不考虑束流空间电荷影响时,编程计算结果与Superfish模拟结果一致。由考虑束流空间电荷影响的色散方程数值计算结果,可知文献中提出的同轴慢波结构相对论高功率微波产生器工作在准TEM模的π模,频率为7.67 GHz,峰值时间增长率较高,电子束损失的能量与其初始能量之比为34%。这些结果均与文献中的数值模拟结果一致。同时理论分析说明该种器件无论在能量转换效率,还是在产生微波脉冲的上升时间上均具有优势。     

宽谱段共光轴线色散成像光谱仪三棱镜分光系统设计

针对棱镜型成像光谱仪结构复杂、具有严重的色散不均匀性,进行了共光轴线色散棱镜式宽谱段成像光谱仪研究。利用棱镜的色散公式建立了对称型三棱镜组合分光结构的数学模型,获得了满足直视结构的棱镜组合,并在此基础上分析影响棱镜组色散线性因素：棱镜材料的折射率和色散率对棱镜组线色散影响比较大,入射角度对其影响比较小,并提出改善色散线性的方法,获得了满足线色散要求的棱镜组合的折射率条件,从而为共光轴结构的线色散棱镜式成像光谱仪初始结构的选择提供了重要理论依据。在工作波段为400~1 000 nm、中心波长偏向角为0°、最大色散角为0.6°、光谱仪系统数值孔径NA为0.18、光谱分辨率为5 nm条件下,实现共光轴三棱镜分光系统的线色散设计,最后利用ZEMAX进行了模拟分析表明,理论计算结果与实际仿真结果基本相符。     

Dispersion Characteristics of Coaxial Circular-Arc-Groove Slow-Wave Structure

The coaxial circular-arc-groove periodic slow-wave system for relativestic traveling wave tubes (RTWT) is presented in this paper. To analyze the field in the groove region, the continuous profile of the circular arc is approximately replaced by a series of rectangular steps and the field continuity at the neighboring steps is deduced. The dispersion equation of the coaxial circular-arc-groove slow-wave structure is derived by the matching conditions at the interface between the groove region and central region. The influence of various circuit parameters on the dispersion relation is investigated by the numerical calculation.     

双频相对论返波振荡器的数值模拟

 提出了X波段双频两段式同轴相对论返波振荡器的物理模型,推导了该结构在冷腔时的TM0n模式色散方程,数值求解了两段式同轴波纹慢波结构TM01模色散曲线;用粒子模拟软件对其结构和电磁参数进行分析研究,优化得到的结构参数为第一、二段分别为10个和4个周期数,周期长度分别为0.50 cm和 0.73 cm,波纹幅值分别为0.13 cm和0.21 cm,平均半径为2.9 cm,同轴间隙为2.1 cm。结果表明:在环形相对论电子注电压为510 kV、电流为9.4 kA,引导磁场为0.7 T的条件下,器件得到了X波段稳定的高功率双频微波输出,其平均功率约为0.75 GW,平均功率效率为15.6%。     

薄环形等离子体介质切伦柯夫脉塞

 理论分析了无限大引导磁场情况下的薄环形等离子体介质切伦柯夫脉塞。得出了通入相对论电子注时行列式形式的热腔色散方程,并求出了波增长率。针对不同等离子体密度下,对色散方程以及波增长率进行数值计算和模拟验证。研究发现与电子注作用的主要模式为低频等离子体模式中的前两个模式,随着等离子体密度的升高,脉塞中心工作频率升高、增益变大、带宽明显变宽,由模拟结果可以看出:等离子体频率为4.5×10¹⁹ m^-3时对应着最大的输出功率为80 MW,效率为19.75%,频率为15.55 GHz,继续增大等离子体密度虽然可以使输出频率进一步提高,但是同时会使输出功率迅速下降。     

填充等离子体的介质同轴波导中的切伦科夫辐射

 利用自洽线性场理论，导出了薄环形相对论电子注通过填充等离子体的介质同轴波导中的注波互作用色散方程，得到了注波互作用产生切伦科夫辐射的同步条件和波增长率。分析了填充等离子体后的波与电子注之间的能量交换及等离子体密度对色散特性、波增长率和注波能量交换的影响。分析结果表明：切伦科夫辐射是由沿介质同轴波导传播的慢波与沿薄环形相对论电子注传播的负能空间电荷波耦合所致，且其耦合强度与电子注的密度成正比；输出频率和波增长率随着填充等离子体密度的增大而提高；保持一定的输出频率，增大电子注的束流可得到高的微波输出功率。     

Microwave properties of composites with glass coated amorphous magnetic microwires

The complex permittivity and permeability of composites filled with Fe-based microwires are measured in a coaxial line at frequencies from 0.01 to 10 GHz.The samples under study consist of closely packed wire sections with various orientations relative to wave vector. The composites, where the wires are collinear to the coaxial axis, are found to be low permeable. Their permittivity has frequency dispersion governed by the length of the wire and its linear impedance. The middle section of the wire has higher impedance than that of the end sections where the regular domain structure is distorted. Magnetic bias parallel to the wire axis affects the linear impedance and parameters of dielectric absorption of a composite, the effect is proportional to bias strength. The samples of a coil-type structure, where the wires are wound around the coaxial axis, display the intensive magnetic absorption attributed to the domain wall motion. The absorption takes place in the megahertz band, at microwaves the permeability is close to unity. The microwave properties of diluted composites filled with randomly oriented permeable wires are discussed.     

螺旋线厚度对螺旋线慢波结构高频特性的影响

在螺旋坐标系下采用近似场匹配法研究了厚度较厚的螺旋线慢波结构的高频特性,得到了其色散方程,并数值计算了螺旋线厚度对慢波系统的相速的影响。结果表明:随螺旋线厚度的增加,慢波结构的色散曲线变得平坦,色散变弱,带宽增加。与软件仿真结果及Hook的螺旋线模型对比表明:采用近似场匹配法的计算结果与CST仿真吻合得更好,比Hook模型具有更高的准确性,从而证明所采用理论方法的有效性。     

Solitons of the KP equation in dusty plasma with variable dust charge and two temperature ions: energy and stability

The propagation of nonlinear waves in dusty plasmas with variable dust charge and two temperature ions is analyzed. By using the reductive perturbation theory, the Kadomtsev-Petviashivili (KP) equation is derived. A Sagdeev potential has been investigated. This potential is used to study the stability conditions for existence of solitonic solutions. Also, it is shown that a rarefactive soliton can exist in most of the cases. The energy of the soliton has been calculated and by using the standard normal-mode analysis a linear dispersion relation has been obtained. The effects of variable dust charge on the amplitude, width and energy of soliton and its effects on the angular frequency of linear wave are also discussed.     

同轴周期慢波结构色散特性的通用数值解法

 运用场匹配法和傅里叶级数理论,提出一种原则上可数值求解任意同轴周期慢波结构色散特性的方法,给出了同轴慢波结构TM_0n模的色散方程。基于该方法,编制了Matlab程序,给出了同轴波纹波导和同轴双波纹波导色散特性,以算例形式分析计算了同轴盘荷波导的色散特性。数值计算结果与多维全电磁模拟软件结果进行比较,证明了该数值算法的准确性和可靠性。     

填充多层互易手征介质金属同轴线传播特性

 采用在圆柱坐标系中分离变量的方法，推出填充多层互易手征介质的金属同轴线各层电磁场之间的关系，得到其模式特征方程和圆波导模式特征方程，给出了填充两层手征介质金属同轴线部分模式的色散特性的数值计算结果，分析了手征介质参量及两层手征介质厚度变化等对手征同轴线传播特性的影响。如果互易手征介质的手征参数等于零，可得填充普通介质的同轴线的模式特征方程。与填充普通介质的同轴线中的模式相比，手征同轴线中的模式发生了分叉。当同轴线中所填介质的折射率增大时，其模式归一化截止频率和进行基模单模传输的带宽归一化频率都将减小。     

阶梯槽交错双栅慢波结构高频特性理论和模拟

本文基于一种阶梯槽交错双栅周期慢波结构模型,获得了该结构中的电磁场分布公式.通过场匹配方法,求出了该结构的高频色散方程和耦合阻抗表达式.以W波段行波管用的阶梯槽交错双栅为例,利用本文公式和CST-MWS电磁软件比较计算了色散和耦合阻抗特性,分析了阶梯尺寸参数对高频特性(基模色散、+1次空间谐波归一化相速和耦合阻抗)的影响.结果表明,理论和CST-MWS软件模拟有很好的一致性;相对矩形交错双栅,改善了色散特性,拓展了基模带宽,同时具有足够大的耦合阻抗和适合工程应用的机械强度,在一定程度上可以弥补矩形交错双栅周期慢波结构的不足.     

双脉冲高功率脉冲调制器的设计

采用螺旋线和折叠线技术相结合的方法,设计了一种基于水介质高功率脉冲调制器。该调制器采用了两个开关,通过控制两个开关的导通时刻,可以在两个负载上得到脉冲长度相等的两个脉冲。对该种折叠型传输线的波过程进行了详细分析,给出了过渡段部分阻抗等参数对负载电压的影响;用Pspice电路软件对脉冲形成线的充电电压和二极管电压、电流进行了模拟;最后利用高压同轴电缆,对该种类型调制器进行了低压情况下的验证实验,实验结果与理论分析、模拟研究一致。此种类型的调制器具有结构紧凑、可同时输出两个脉冲的优点。