Linear Theory of the Coaxial Ridge-Loaded Helical Groove Waveguide

The coaxial ridge-loaded helical groove waveguide, an all-metal slow-wave circuit, has advantages of good heat dissipation and great size, and thus is suitable for use of millimeter TWTs. In this paper, the dispersion equation of the circuit with an annular electron beam is obtained according to self-consistent field theory. The influence of various electron beam parameters on the small signal gain is investigated and discussed by the numerical computation.     

Wave Propagation Along a Helical Step-Loaded Groove Waveguide

A new kind of helical groove structure, step-loaded groove waveguide is presented and analyzed in this paper. The dispersion equation of this structure is derived by means of a field-matching method. This equation may be reduced to the dispersion equation of helical ridge-loaded structure and rectangular one. In order to demonstrate the influence of the step on the dispersion properties, the comparison of the dispersion characteristics is made in these helical rectangular and modified rectangular groove structures. Form the analysis, it is shown that the step loading tends to reduce the dispersion of the helical groove circuit and the step-loaded structure has the weaker dispersion compared with the rectangular one or the ridge-loaded one. The effect of the step shape on the wave properties is also discussed under the deep groove case. The theoretical results explicitly indicate that the V-like step-loaded structure has the weakest dispersion in all step-loaded structures.     

The Analysis of Hole-Gap Helical Groove Waveguide

The hole-gap helical groove waveguide, as a all-metal slow-wave circuit, has advantages of good heat dissipation and great size, and thus is suitable for use of mm TWT. By means of an approximate field theory, the expressions of the dispersion equation and the coupling impedance of the hole-gap helical groove waveguide is obtained in this paper. The influence of various circuit dimensions on the dispersion relation and the coupling impedance is discussed by the numerical computation.     

Dielectric effect on the rf characteristics of a helical groove travelling wave tube

A new type of partial-dielectric-loaded helical groove slow-wave structure (SWS) for millimetre wave travelling wave tube (TWT） is presented in this paper.The radio-frequency characteristics including the dispersion properties,the longitudinal electric field distribution and the beam-wave coupling impedance of this structure are analysed.The results show that the dispersion of the helical groove circuit is weakened,the phase velocity is reduced and the position of the maximum Ez is moved from the mouth to the inside of the groove after partially filling the dielectric materials in the helical groove SWS.Therefore,the dielectric-loaded helical groove SWS is suitable for a multi-beam TWT with broad band and high gain.     

具有任意槽的矩形波导栅慢波结构高频特性的研究

将任意形状槽的连续轮廓近似用一系列相连的矩形阶梯近似，利用各阶梯面上导纳的匹配，以及槽与互作用区边界场的连续与匹配条件，获得了具有任意槽的矩形波导栅慢波结构的色散方程和耦合阻抗的表达式，并进行理论上的验证.加工制作了矩形槽波导栅模型，冷测表明理论值与测量值相吻合.分别求解几种特殊槽形矩形波导栅慢波结构的色散特性及耦合阻抗，其中，三角形结构的色散和耦合阻抗均最弱，而倒梯形结构色散最强，耦合阻抗最大. 关键词： 矩形波导栅 任意槽 色散特性 慢波结构     

曲折圆形槽波导慢波系统的高频特性

 对曲折圆形槽波导新型慢波系统的高频特性进行了研究，通过理论分析和数值计算，得到了它的色散曲线和耦合阻抗表达式，并分析了结构参数变化对色散特性和耦合阻抗的影响。研究表明：当周期变小时色散减弱，耦合阻抗增加；而增大直波导长度时色散变弱，但同时耦合阻抗也会下降。因此较小的周期有利于改善曲折圆形槽波导慢波电路的高频特性。鉴于这种电路的耦合阻抗较低，可以适当地减小直波导长度来提高耦合阻抗。曲折槽波导结合了曲折波导散热能力强、色散特性好、容易加工和槽波导单模工作、低损耗、大尺寸等优点，在毫米波及亚毫米波段的行波管中具有较好的发展前景。     

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.     

纵向金属导体加载螺旋慢波特性的理论研究

 考虑角向均匀谐波与非翼片区角向高次谐波的影响，运用场匹配法参考脊加载环板慢波结构的边界条件，推导得到翼片加载螺旋慢波结构的色散特性方程，在此基础上推导得到有限翼片加载下的耦合阻抗和衰减常数。运用MAFIA软件对该结构进行模拟计算，将理论结果与模拟计算和部分实验数据进行比较，其曲线趋势基本一致，反映了该结构的物理本质，本方法为各种类型的翼片加载螺旋慢波特性的计算提供了一种参考手段。     

同轴任意槽形周期圆波导慢波结构色散特性的研究

用阶梯近似的方法分析任意槽形加载的圆波导慢波系统，利用各阶梯相邻面的导纳匹配条件 以及中心互作用区与加载区的场匹配条件，获得了任意槽形加载周期慢波结构的统一色散方 程. 利用该色散方程，得到色散特性与CST MWS仿真软件模拟结果良好符合. 分别求解几种 特殊槽形加载慢波结构的色散特性及耦合阻抗，其中，三角形结构色散和耦合阻抗均最弱， 而倒梯形结构色散最强，耦合阻抗最大. 关键词： 任意槽形 慢波结构 色散特性 行波管     

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。     

Accurate analysis of arbitrarily-shaped helical groove waveguide

This paper presents a theory on accurately analysing the dispersion relation and the interaction impedance of electromagnetic waves propagating through a helical groove waveguide with arbitrary groove shape, in which the complex groove profile is synthesized by a series of rectangular steps. By introducing the influence of high-order evanescent modes on the connection of any two neighbouring steps by an equivalent susceptance under a modified admittance matching condition, the assumption of the neglecting discontinuity capacitance in previously published analysis is avoided, and the accurate dispersion equation is obtained by means of a combination of field-matching method and admittance-matching technique. The validity of this theory is proved by comparison between the measurements and the numerical calculations for two kinds of helical groove waveguides with different groove shapes.     

脊加载螺旋槽行波管的小信号增益计算

脊加载螺旋槽行波管是一类新型毫米波大功率器件,给出了此结构中引入电子注后的“热”色散方程,并利用“牛顿”下山法求解了此复系数超越方程.通过数值计算给出了一个工作电压为20kV频率为474GHz的脊棱加载慢波结构的具体尺寸,并对此结构中小信号增益随脊尺寸的变化情况及电子注参数对其影响进行了研究,计算结果表明：此结构适宜于作为高增益窄带毫米波大功率行波管的慢波线,其3dB增益带宽为34%;为了展宽其工作带宽,可以适当减小间隙宽度,也可在一定范围内提高电子注电流.给出的理论对于研制此类行波管具有一定的指导意 关键词：     

矩形栅慢波系统的高频特性分析

 对于矩形栅这一经典的慢波结构，采用场匹配法来分析其慢波特性，进而得到其耦合阻抗。其中对槽区内的场处理，保留其高次项，表示为一无限本征驻波之和的形式。然后通过数值实例具体分析了矩形栅的两种典型结构：浅槽栅和深槽栅。当增大槽深后，色散增强，系统通带变窄，同时耦合阻抗有明显增大，工作点移向前向波区，适合用在放大器的慢波结构上。     

DIELECTRIC EFFECT ON THE RADIO-FREQUENCY CHARACTERISTICS OF A RECTANGULAR WAVEGUIDE GRATING TRAVELING WAVE TUBE

A new type of partial-dielectric-loaded rectangular waveguide grating slow-wave structure (SWS) for millimeter wave traveling wave tube (TWT) is presented in this paper. The radio-frequency characteristics including the dispersion properties, the longitudinal electric field distribution and the beam-wave coupling impedance of this structure are analyzed. The results show that the dispersion of the rectangular waveguide grating circuit is weakened, the phase velocity is reduced and the position of the maximum E _z is basically invariant after partially filling the dielectric materials in the rectangular waveguide grating SWS. Although the coupling impedance decreases a little, it still keeps above 40 Ω.     

螺旋槽回旋行波管高频特性分析

 在Foulds等人对螺旋槽结构进行深入分析的基础上，考虑了槽区内高次模式对慢波结构高频特性的影响。结果表明：槽宽较小时，结论与其结论吻合较好； 槽宽较大时，计算结果与其有较大差别。此外，讨论了螺旋槽结构参数对高频特性的影响，结果表明：除槽宽外的其它结构参数固定时，存在一个最佳的δ/L值，可以获得较弱的色散和较大的横向场幅值，适合做回旋行波管互作用结构。     

Folded waveguide circuit for broadband MM wave TWTs

In millimeter wave band, the folded waveguide circuit exists some advantages such as wide operating frequency band, high mechanism strength, better heat disspation, easy fabrication and lower cost. It is expected that contradictory between broadband and high power in millimeter wave range can be solved by using the folded waveguide circuit. Computational results of dispersion character and coupling impedance of the folded waveguide are given. It is shown that the folded waveguide has wide bandwidth character in millimeter wave band.     

Modified Tunneladder Slow-Wave Structures for High-Power Millimeter-Wave TWTs

In this paper, five modified Tunneladder slow-wave structures (SWS), the ridge-loaded stub-supported meander line with circular electron tunnel (CET-RSML), ring-plane frame line (RPFL), the ridge-loaded thick ladder line (RLTLL), the ridge-loaded pole-piece folded-waveguide circuit (RLPFWL), and the double-period Tunneladder line (DPTL) were discussed. The dispersion characteristics and the interaction impedances of the five modified Tunneladder SWS were calculated by simulation and the corresponding analytic models. The calculation results explain that the CET-RSML and the RLTLL hold wider bandwidth in comparison with the Tunneladder, when the volume dimensional lengths are same. When the bandwidth is definite, the interaction impedance of RLTLL can be higher than Tunneladder, but that of CET-RSML can’t. The dispersion curves of the RLPFWL and the DPTL are more linear in comparison with Tunneladder, but the interaction impedances are very low. Supported by the National Natural Science Foundation of China, under Grant No. 60532010.     

Investigation of a wideband folded double-ridged waveguide slow-wave system

The folded double-ridged waveguide structure is presented and its properties used for wide-band traveling-wave tube are investigated.Expressions of dispersion characteristics,normalized phase velocity and interaction impedance of this structure are derived and numerically calculated.The calculated results using our theory agree well with those obtained by using the 3D electromagnetic simulation software HFSS.Influences of the ridge-loaded area and broad-wall dimensions on the high frequency characteristics of the novel slow-wave structure are discussed.It is shown that the folded double-ridged waveguide structure has a much wider relative passband than the folded waveguide slow-wave structure and a relative passband of 67% could be obtained,indicating that this structure can operate in broad-band frequency ranges of beam-wave interaction.The small signal gain property is investigated for ensuring the improvement of bandwidth.Meanwhile,with comparable dispersion characteristics,the transverse section dimension of this novel structure is much smaller than that of conventional one,which indicates an available way to reduce the weight of traveling-wave tube.     

Analysis of Performances for Broadband Millimeter Wave Folded Waveguide TWTs

On the basis of computation of dispersion and coupling impedance for folded waveguide circuit (FWC), main performances: interact coefficient, saturated gain and output power are analyzed. Computation shows that if FWC is used in MMW amplifier, high power and wide band can be easy reached.     

Study of the double rectangular waveguide grating slow-wave structure

A slow-wave structure (SWS) with two opposite gratings inside a rectangular waveguide is presented and analysed. As an all-metal slow-wave circuit, this structure is especially suited for use in millimetre-wave travelling wave tubes (TWTs) due to its advantages of large size, high manufacturing precision and good heat dissipation. The first part of this paper concerns the wave properties of this structure in vacuum. The influence of the geometrical dimensions on dispersion characteristics and coupling impedance is investigated. The theoretical results show that this structure has a very strong dispersion and the coupling impedance for the fundamental wave is several tens of ohms, but the coupling impedance for --1 space harmonic wave is much lower than that for the fundamental wave, so the risk of backward wave oscillation is reduced. Besides these, the CST microwave studio is also used to simulate the dispersion property of the SWS. The simulation results from CST and the theoretical results agree well with each other, which supports the theory. In the second part, a small-signal analysis of a double rectangular waveguide grating TWT is presented. The typical small-signal gain per period is about 0.45 dB, and the 3-dB small-signal gain bandwidth is only 4\%.