考虑螺带厚度的纵向导体加载螺旋慢波特性分析

考虑非翼片区角向高次模式以及螺带厚度,运用场匹配方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;并运用MAFIA软件对该结构进行模拟计算,将理论结果与模拟计算进行比较,其误差范围基本满足设计精度的要求,并讨论了不同翼片结构参数对色散特性的影响,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方法。     

一种有限厚度翼片加载螺旋线色散特性及耦合阻抗研究

翼片加载螺旋线慢波结构广泛应用于大功率、宽频带行波管中.一般的计算未考虑翼片加载所引起的角向空间谐波,本文考虑空间谐波,建立了有限厚度翼片加载螺旋线慢波结构的模型,推导出实用的色散方程和耦合阻抗表达式.利用导出的方程对实际行波管的螺旋慢波结构进行计算,并与测量结果和简单翼片模型进行了比较.首次通过分析的方法得到加载翼片有最佳中心夹角(θ)存在.     

Effects of Beam and Magnetic Field Parameters on Highly Competing TE01 and TE21 Modes of Vane Loaded Gyro-TWT

In this paper, the dispersion relation for a vane-loaded cylindrical waveguide, considering the azimuthal harmonic effects arising from the azimuthal periodicity of the vanes, excited in transverse electric (TE) modes and the gain for a gyro-TWT have been presented. The effects of beam and magnetic field parameters on two highly competing modes have been studied.     

GAIN AND BANDWIDTH ANALYSIS OF A VANE-LOADED GYRO-TWT

Theoretical investigation of the peak-gain and 3-dB bandwidth of the vane-loaded gyro-traveling wave tube (gyro-TWT) amplifier in the small-orbit TE₀₁ waveguide mode configuration at 35 GHz has been presented. The vane-loaded gyro-TWT enjoys higher gain and bandwidth compared to that of the smooth-wall device. In the analysis, the azimuthal harmonic effects generated due to the angular periodicity of vanes in the wedge-shaped metal vane-loaded cylindrical waveguide interaction structure have been taken into account in the cold (beam-absent) dispersion relation only.     

Nonlinear Eulerian hydrodynamical analysis of helix traveling-wavetubes for harmonic generation and its control

Eulerian hydrodynamics was developed to study the nonlinear problem of second harmonic generation in a helix traveling-wave tube (TWT). A closed-form expression for the second-harmonic component of RF output power was obtained. The method required the specification of the dispersion and interaction impedance characteristics of the helical slow-wave structure (SWS) used in the device, obtainable by the field analysis of the SWS. Care was taken however to restrict the present Eulerian theory to the correct regime, which was found in terms of the RF input power drive and the device interaction length, by validating the theory against the more accurate Lagrangian theory. Within this regime, that was below the saturation level of the device, the effect of the dispersion of the SWS on the second harmonic generated in the device was studied. It was found that, irrespective of whether the dispersion of the SWS is positive or negative, the second harmonic content of the device decreased with the amount of the dispersion. Furthermore, though both the fundamental and the second harmonic content of the device decreased with the distributed loss on the SWS, the second harmonic relative to the fundamental showed a minimum at an optimum value of the distributed loss     

双注多翼片加载的角向夹持角度对数曲折线慢波结构

针对角向夹持的角度对数周期曲折线慢波结构,提出了展宽其工作带宽、降低其工作电压的新方法.通过翼片加载技术,可以对慢波结构的色散特性进行修正,从而使得其带宽得到有效展宽.通过数值模拟仿真,得到无翼片加载的慢波结构以及多翼片加载的慢波结构的3 dB带宽分别为2. 5 GHz、3 GHz,工作电压分别为5 450 V、4 650 V.研究表明,翼片加载结构可以有效降低角度对数周期曲折线慢波结构的工作电压,以及展宽其工作带宽.     

毫米波行波管返波振荡的仿真研究

该文利用HFSS仿真了工作在Ka波段的螺旋线、反绕双螺旋线及耦合腔等慢波系统,通过傅里叶分析得到空间谐波,进而分析和比较了上述慢波系统的返波振荡特性.结果表明:螺旋线慢波系统中出现明显的角向谐波次数和轴向谐波次数不相等的窄问谐波分量,在π模附近,有产生返波振荡的危险:而反绕双螺旋线通过提高基波耦合阻抗及可工作的归一化频率来提高了抑制返波振荡的能力;为了避免返波振荡,耦合腔工作频带的选择应尽可能远离单腔相移为π,2π的频点.     

一种具有新型分立介质支撑的翼片加载螺旋带慢 波结构的研究

本文研究了一种具有新型分立介质支撑的翼片加载螺旋带慢波系统,该种慢波系统具有较高的功率容量和较宽的带宽.通过用切比雪夫多项式来展开螺旋带上的面电流,用真空层来模拟螺旋带的厚度,用均匀分层介质来等效新型分立介质支撑,考虑到过渡连接金属块的影响,用场论的方法得到了非常实用的色散方程和耦合阻抗的表达式,同时进行了HFSS模拟,发现用场论的方法所得出的结果与用HFSS模拟的结果吻合良好.本文的结果对这种新型慢波结构的设计具有指导意义.     

任意槽形螺旋槽慢波结构的色散方程

在本文的分析中,将任意槽形的螺旋槽的连续轮廓近似用一系列相连的矩形阶梯代替,利用各阶梯面上导纳的匹配,以及槽与中心互作用区边界场的连续和匹配条件,获得了任意形状螺旋槽慢波结构的色散方程;同时加工制作了一半圆形螺旋槽模型,对其色散特性的冷测实验表明理论与测量值相吻合。     

The Small Signal Analysis of a Centered Dielectric-Rod Loaded,Arbitrarily-Shaped Helical Groove Traveling-Wave-Tube

Properties of traveling wave-beam interaction in a centered dielectric-rod loaded, arbitrarily-shaped helical groove slow-wave structure (SWS) are investigated for a thin annular electron beam. The “hot” dispersion equation is obtained by means of the self-consistent field theory, and the small signal analysis is carried out including the effects of the dielectric-rod parameters and the groove shapes. The numerical results show that the bandwidth of the helical groove TWT is expanded by loading dielectric-rod, however, the small-signal gain is reduced; and when the groove shape changes from the swallow-tail shape to the triangle shape, the working frequency increases , while the peak gain decreases.     

V形杆夹持翼片加载螺旋线的色散特性

Ｖ形杆夹持、翼片加载的螺旋线但波结构很适合于宽频带行波管应用。本文对不同的翼片加载结构的色散特性进行了计算，计算数据与实验测量结果一致性较好。最后讨论了Ｖ形杆与圆形杆夹待时的介质负载和色散特性。     

Experimental Study of a Slot Antenna Excited by a TE011 Mode Coaxial Cavity

A slot antenna is developed to excite the high harmonic waveguide mode for generating large-area plasmas. This antenna consists of a TE₀₁₁ mode coaxial cavity with the axial slots positioned on equal interval on the inner wall. The waves radiated from those slots can excite the high harmonic mode in the central area. With the azimuthal symmetric wave field of the TE₀₁₁ mode, the number of the slots can be chosen to match the field pattern of the high harmonic mode. In this report, the dispersion relation of the coaxial waveguide, the coupling scheme and the mode competition of the cavity are studied. A method has been successfully developed to suppress the TE₁₂₁ mode which is the most competing mode to the TE₀₁₁ mode.     

Analysis of the Dispersion Characteristic and Interaction Impedance of a Tape Helix Slow Wave Structure with Novel Supporting Mode

In order to enhance the power capability of the helix travelling wave tube, a novel tape helix slow wave structure (SWS), which is supported by helically arrayed radial dielectric-support posts, is developed. Each dielectric post can be easily brazed with the tape helix and the metal envelope by means of a special soldering. This kind of supporting mode can protect the dielectric supporting posts from being broken by the thermal stress in the case of high temperature. A hybrid model is set up in consideration of the influences of both the radial thickness of the tape helix and these discrete dielectric-support posts. The dispersion equation and interaction impedance of the helical SWS are obtained. The calculated results using this hybrid model presented in the paper show good agreements with the HFSS simulation results. All the results presented here can provide a good basis for designing the novel tape helix SWS.     

Multi-Cycle Terahertz Emission from <Emphasis Type="Italic">β</Emphasis>-Barium Borate

We report the observation of strong narrowband terahertz emission at 10.6 THz from the common nonlinear second harmonic generation crystal β-barium borate crystal excited by 40 fs laser pulses at a 800 nm center wavelength. The emitted THz field amplitude is linear with incident pump energy with no saturation observed up to 2 mJ of pump pulse energy, and exhibits a crystal azimuthal angular dependence consistent with an optical rectification process. The narrowband emission can be explained by the large dispersion caused by optical phonons in the vicinity of the emission energy.     

Effect of conductive perturber diameter on nonresonant measurementof interaction impedance for helical slow-wave structures

The measurement accuracy of the interaction impedance for a helical slow-wave structure (SWS) using the nonresonant perturbation method has been studied using conductive wire perturbers with different diameters. Data obtained by the measurement were compared with a rigorous numerical analysis. It is shown that the measured values of the interaction impedance for the helical SWS converge to those obtained by using a three-dimensional finite-element computational method when the diameter of the perturber is reduced to less than 10% of the helix diameter     

Validation of HFCS-I on Calculation of High-Frequency Parameters of Helical Slow-Wave Structures

To validate HFCS-I, a newly developed design tool for high frequency circuits of microwave tubes, the high-frequency parameters (including dispersion, interaction impedance and attenuation constant) of a typical helical slow-wave structure (SWS) for millimetre wave travelling-wave tube are calculated by HFCS-I and MAFIA. Both the direct calculation method and the Non-Resonant Perturbation (NRP) technique are adopted to get the interaction impedance. The obtained high-frequency parameters from HFCS-I and MAFIA are compared in detail and the consistency has proved the reliability and validity of HFCS-I.     

大直径波纹内导体同轴慢波结构特性的研究

提出了易以加工的大直径波纹内导体相对论返波振荡器慢波结构,推导了这种慢波结构的冷色散方程和耦合阻抗计算公式,数值计算并详细分析了相关结构参数对TM_0n模式色散曲线分离度以及TM₀₂模式的高频场耦合阻抗的影响.结果表明:慢波结构周期、波纹深度以及电子注平均半径都对高频场耦合阻抗有影响;这种慢波结构在抑制模式竞争、以及在低引导磁场下工作等方面都有较大的优势.     

太赫兹扩展互作用振荡器的矩形耦合腔特性研究

本文选用矩形耦合腔作为太赫兹扩展互作用振荡器(EIO)的慢波结构,鉴于其结构的复杂性,采用等效电路方法计算其色散.详细研究了腔体和耦合槽的电路参数,计算了不同结构尺寸、圆形和矩形电子通道的0.12THz和0.225THz慢波结构的色散特性.并采用专业电磁软件,研究了不同结构参数下的色散特性、耦合阻抗和特征阻抗.通过对色...     

Wave Properties of A Free Elliptical Helix Slow-Wave Structure with Arbitrary Eccentricity

This paper gives the investigations of the fundamental wave of a free elliptical helix slow-wave structure (SWS) with arbitrary eccentricity. The wave properties including the phase velocity characteristics, interaction impedance and the longitudinal electric field distribution of this mode has been fully studied. It is found that, when the eccentricity increases, the interaction impedance and the operating frequency of such SWS will be improved, which allows to have a higher gain and operating in a higher frequency band. Furthermore, the field configuration is different from that of a round helix; the azimuthal distribution of the E-field follows with the angular Mathieu function of the first kind, even with mode of zero. In radial, E-field is elliptical surface wave. When the eccentricity tends to zero, all the characteristics will be smoothly degenerates to the case of round helix correspondingly.     

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.