220GHz折叠波导慢波结构的有损参数化模型（英文）

建立了自洽的考虑波导璧损耗的折叠波导等效电路模型,用来计算该慢波结构周期TE10模式中各次空间谐波的相速度,耦合阻抗和线衰减系数.分析结果将会用到220 GHz折叠波导返波管一维束波互作用模型的计算中.当微波频率上升到太赫兹波段时,粗糙波导表面电流导致的壁损将不能再忽略不计.进一步研究表明,起振电流和输出功率水平将和损耗特性的计算密切相关.从原有模型发展而来的有损电路模型可以给出更准确损耗估计.建立了折叠波导慢波线三维谐振腔模型来验证本文的等效电路理论,有较好的吻合.采用了该理论导出参数的一维束波互作用模型和三维数值PIC方法同样有很好的一致性.     

W波段折叠波导慢波结构设计及三维注波互作用模拟

本文综合分析了折叠波导的几何尺寸和电子束参数，运用电磁场软件MAFIA的粒子模拟程序对三维折叠波导慢波结构进行了模拟．模型中，电磁波通过波导模式导入；为了克服较大空间电荷效应造成的电子注发散，使用了纵向聚焦磁场．基于三维互作用模型得到了W波段折叠波导的模拟结果，该结果可以对折叠波导慢波结构的三维互作用性能进行预测和分析．     

折叠波导慢波电路的传输特性

研究了新型慢波结构折叠波导慢波电路的传输特性 ,利用等效电路法计算了折叠波导电路的色散特性、耦合阻抗和止带。分析和计算表明 ,该电路很适合用作短厘米波和毫米波大功率行波管的慢波结构。     

0.67 THz折叠波导慢波结构损耗的计算

在太赫兹频段,损耗对折叠波导慢波结构的特性有显著影响。提出一种计算折叠波导慢波结构损耗的理论模型,推导出弯曲波导的衰减系数。分别使用理论模型和商业仿真软件计算了0.67 THz折叠波导慢波结构的损耗,二者的计算结果吻合较好,表明理论模型有较高的精确度。最后,使用理论模型分析了0.67 THz折叠波导慢波结构的结构参数变化对损耗特性的影响。     

亚毫米波折叠波导慢波结构的损耗特性研究

损耗是慢波结构的重要参量之一.采用理论与仿真的方法分析了在亚毫米波段(220 GHz)折叠波导慢波结构的导体损耗.在理论模型计算了弯曲波导段的衰减系数,并考虑了波导内表面粗糙度对电导率的影响,从而使模型更接近实际情况.计算结果表明,弯曲波导段的衰减常数大于直渡导段,而且理论模型计算出的每周期折叠波导电路的损耗与高频仿真软件HFSS的结果吻合较好,说明理论模型有较高的精确度.在此基础上,分析了慢渡结构参数变化对损耗的影响.     

螺旋折叠圆波导慢波结构的特性

本文介绍螺旋折叠圆波导慢波结构的主要特性：色散关系和互作用阻抗。计算表明，该电路在ｒａ（径向传播参量）较小时，色散强于螺旋带慢波线，但其互作用阻抗较高。若它工作于较大ｒａ值，色散变弱，而仍具有高的互作用阻抗，故可作为宽频带高功率微波放大的电路。     

W波段大功率集成极靴式互作用结构研究

针对W波段大功率折叠波导行波管的技术难点,提出了一种一体式加工的集成极靴式互作用结构,该结构将直角型折叠波导嵌入到极靴中,实现注-波互作用结构与聚焦系统的集成,提高周期永磁系统的聚焦能力,再通过增加阴极发射的电子注电流,实现功率的提升。文中首先介绍了集成极靴式互作用结构,提供该结构中慢波结构的尺寸参数,计算其色散特性及耦合阻抗曲线,并设计了相应的磁聚焦系统。最终对互作用结构进行仿真模拟,在90~100 GHz频带内可获得高于700 W的饱和输出功率。带内饱和增益均小于20 dB,可有效防止自激振荡的产生,该互作用结构可广泛应用于级联功率放大模块的后级放大器中。     

0.22 THz折叠波导行波管设计

在一支0.22 THz折叠波导行波管样管的模拟设计和实验研究基础上,对该样管进行了优化设计。对慢波损耗特性、慢波结构的尺寸冗余度进行了研究,对结构加工进行了进一步的考虑,对样管的实验研究进行了详细讨论并论述了新慢波结构的设计。采用HFSS软件结合大信号理论计算进行模拟,结果表明,折叠波导行波管的输出功率不低于100 mW,带宽不低于5 GHz。     

0.22 THz宽带折叠波导慢波结构的设计

通过对折叠波导的理论分析,提出一种快速设计折叠波导慢波结构的方法。优化设计了中心频率为0.22 THz的折叠波导慢波结构,分析了结构参数对高频特性的影响。为防止振荡,仿真中采用截断的慢波结构。互作用仿真表明,在电子注电压为16 kV,电流为10 mA情况下,中心频率处增益为23.9 dB,输出功率为1.2 W。其中3 dB带宽大于14 GHz(0.214 THz~0.228 THz),带内输出功率大于0.5 W,在7 GHz(0.217 THz~0.224 THz)范围内输出功率大于1 W。     

0.14 THz大功率回旋行波管前级激励源粒子模拟研究

以折叠波导行波管作为大功率回旋行波管的前级激励信号源,利用电磁仿真软件HFSS和粒子模拟软件(CST粒子工作室),对0.14 THz微电真空折叠波导行波管慢波结构的色散特性、耦合阻抗进行计算分析,然后对折叠波导行波管束波互作用过程进行粒子模拟,最后通过粒子模拟得到该折叠波导行波管的增益、工作电压、电流等工作特性参数。在电压为13.9 kV、电流为16 mA,输入功率为5 mW的条件下,输出功率为5 W,线性增益为30 dB,带宽3.7 GHz,最大输出功率为6.2 W,该结果为0.14 THz大功率回旋行波管实现kW量级的功率输出提供功率足够的前级馈入信号奠定了基础。     

矩形波导加载光栅结构的太赫兹振荡器

本文采用矩形波导加载光栅的慢波结构作为太赫兹返波管的高频结构,通过理论分析和电磁仿真研究了该慢波结构的色散特性和互作用阻抗,理论分析结果和仿真结果能很好地吻合。在理论分析的基础上,设计了一个中心频率为340GHz的返波管,经粒子模拟软件计算,在较低电流密度的情况下该返波管输出功率达100mW且可调带宽约30GHz。     

A Tapered Ridge-loaded Folded Waveguide Slow-wave Structure for Millimeter-wave Traveling-wave Tube

This paper presents a tapered ridge-loaded folded waveguide (FWG) slow-wave structure (SWS) for broadband and high power millimeter wave traveling wave tube (TWT). The radio-frequency characteristics including dispersion properties, interaction impedance, S-parameters are analyzed. And based upon these results, the nonlinear large signal performance of the tapered ridge-loaded folded waveguide TWT working in W-band is simulated by 3-D particle-in-cell code. In the same ridge length, the tapered FWG has lower reflection and radio-frequency loss than the normal ridge-loaded FWG. Besides, the tapered ridge-loaded FWG TWT also has higher electron efficiency and larger bandwidth, which is more suitable for millimeter-wave TWT.     

新型慢波系统毫米波行波管研究

研究了三种新型的曲折波导慢波系统,分别是曲折双脊波导、脊加载曲折波导和矩形槽加载曲折波导。给出了其高频特性的理论和仿真结果。然后介绍了基于常规曲折波导和脊加载曲折波导慢波系统的Ka 波段行波管的实验结果。     

Accurate parametric modeling of folded waveguide circuits for millimeter-wave traveling wave tubes

In this paper, results of different models are compared for calculating effective, cold-circuit (beam-free) phase velocities and interaction impedances of folded waveguide (FW) slow wave circuits for use in millimeter-wave traveling wave tubes (TWT). These parameters are needed for one-dimensional (1-D) parametric model simulations of FW traveling wave tubes (FWTWTs). The models investigated include approximate analytic expressions, equivalent circuit, three-dimensional (3-D) finite difference, and 3-D finite element. The phase velocity predictions are compared with experimental measurements of a representative FW circuit. The various model results are incorporated into the CHRISTINE1D code to obtain predictions of small signal gain in a 40-55 GHz FWTWT. Comparing simulated and measured frequency-dependent gain provides a sensitive, confirming assessment of the accuracy of the simulation tools. It is determined that the use of parametric 1-D TWT models for accurate, full band predictions of small signal gain in FWTWTs requires knowledge of phase velocity and impedance functions that are accurate to <0.5% and <10%, respectively. Saturated gain predictions, being approximately half as sensitive to these parameters, appear to require correct specification of phase velocity and interaction impedance to within /spl sim/1% and 20%, respectively. Although all models generate sufficiently accurate predictions of the interaction impedance, not all generate sufficiently accurate predictions of the effective axial phase velocity.     

理论分析毫米波螺旋线行波管慢波系统导体和介质损耗

该文基于夹持杆分层螺旋带模型和3维电磁场模型分析,详细研究了毫米波螺旋线行波管慢波系统的导体和介质损耗。螺旋带模型中介质损耗考虑为纵向传播常数的虚部,给出电磁场的解析解,导体损耗由螺旋线和管壳表面的面电流不连续性获得。3维电磁场模型分析通过本征模法,求解单周期结构的品质因数和周期储能,获得有限导电率导体和夹持杆陶瓷损耗角带来的慢波系统高频损耗。结果表明,毫米波段螺旋线的导体损耗和夹持杆的介质损耗远大于管壳导体损耗,介质损耗与陶瓷损耗角呈线性关系,对高频损耗的影响不可忽略。     

Frequency-selective transmission by a leaky parallel-plate-like waveguide

The phenomena of high frequency-selective transmission of a plane wave by a dielectric two-dimensional (2-D) periodic waveguide, comprising a uniform dielectric layer sandwiched by two finite thickness 2-D periodic structures served as the waveguide wall is described. This structure is termed a leaky parallel-plate-like waveguide because the waveguide walls are not perfect reflection mirrors. The scattering characteristics and dispersion relation, including the phase and attenuation constants, of the 2-D periodic waveguide are thoroughly analyzed with the modal transmission-line method and Floquet theory. The extraordinary open stopbands caused by the contra-flow coupling between a leaky parallel-plate-like waveguide and the leaky waves, which are generated by 2-D periodic structures (waveguide walls), are displayed in the form of the Brillouin diagram. The phase-match condition is used to verify the resonant coupling between the incident plane wave and the leaky parallel-plate-like waveguide modes. Specifically, the transmission peak frequencies are accurately predicted.     

ANALYSIS OF RECTANGULAR WAVEGUIDE GRATING SLOW-WAVE STRUCTURE WITH THE ARBITRARY SHAPED GROOVES

The rectangular waveguide grating slow-wave structure (SWS) with arbitrary shaped grooves is presented and analyzed in this paper. As an all-metal slow-wave circuit, it has properties that can be used in high-power millimeter-wave or sub-millimeter wave traveling wave tube (TWT). The unified dispersion equation and the expression of coupling impedance are obtained in this paper by means of an approximate field-theory analysis, in which the profile of the groove is approximately replaced by a series of steps and the field continuity at the interface of two neighboring steps together with the field matching conditions at the interface between the groove region and the interaction region are employed. A rectangular groove SWS was manufactured and the cold measurement was made. The experimental data are in good agreement with the numerical calculation. The derived transcendental equations are resolved numerically for four classical structures such as rectangular, dovetail, ladder and cosine. Finally, taking the rectangular waveguide grating SWS with rectangular grooves for example, the influences of physical dimensions on dispersion relation and coupling impedance are discussed.     

THz返波管圆波导梳状慢波结构的研究

该文利用三维电磁仿真软件模拟计算了THz圆波导梳状慢波结构的负1次返波的色散和耦合阻抗。结果证实:在430-570GHz频带内,慢波结构内半径为0.175mm,约为中心频率波长的0.292倍;在760-940GHz的频带内,慢波结构内半径为0.1mm,是中心频率处波长的0.392倍。该结构较大的径向尺寸有利于提高电子注通过率。这种结构负1次返波的耦合阻抗较小,基本上小于1 ,很好解释了现有THz返波管的电子效率小于0.01%的事实。     

周期损耗介质加载波导与均匀圆波导间的模式映射

损耗介质环与金属环间隔加载的周期损耗介质波导能够有效地控制各种模式的衰减特性,这对于抑制毫米波回旋行波管放大器的绝对不稳定性和提高其性能具有重要作用.针对应用于Ka波段、TE01模的回旋行波管放大器的周期损耗介质加载圆波导,系统地分析了该周期系统与均匀系统间的模式映射关系.研究表明,当介质层厚度一定时,均匀介质加载波导中的高阶模式可以映射为光滑波导中的低阶模式,且相互映射的模式在中空区域的场型一致.周期系统中的模式表现出复合模式的分布.在一个周期中,介质段和金属段的模式分别映射为均匀介质波导和金属波导中的模式.明确周期介质加载波导系统与均匀波导系统间的模式映射关系是分析发生在这种复杂的互作用回路中的回旋电子脉塞注波互作用的前提,对简化其物理模型具有指导作用.     

Measurement of the complex permittivity of low loss polymer powders in the millimeter-wave range.

An improved measurement method of complex permittivity of low loss polymer powders is suggested. The measurements are done in the mm-wave range using a quasi optical resonator. The 2-D corrugated mode exciter is employed to improve suppression of undesirable higher modes. The model used for reconstructing complex permittivity takes into account ohm losses of metal mesh coupling that provide better accuracy of the reconstructing procedure. An example illustrating this method is reported.