Analysis of the Coaxial Ridge-Loaded Helical Groove Waveguide

The coaxial ridge-loaded helical groove waveguide is proposed in this paper. As an all-metal slow-wave circuit, it has advantages of good heat dissipation and great size, and thus is suitable for use of millimeter TWT. By means of field theory, the expressions of the dispersion equation and the coupling impedance of the coaxial ridge-loaded helical groove waveguide are obtained. The influence of various circuit dimensions on the dispersion relation and the coupling impedance is investigated by the results of 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.     

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.     

圆柱开槽波导FEM放大器数值研究

以圆柱开槽波导、螺旋摇摆器为模型,考虑了电子初始速度零散、引导磁场等效应对放大器饱和特性的影响,导出了自洽的注波互作用三维非线性方程组.并在此基础上编制了相应的计算软件,通过数值分析的方法研究了圆柱开槽波导自由电子激光放大器的饱和效率、频带宽度等高频特性.     

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. Project supported by the National Nature Science Foundation of China (Granted NO.60401005 and 60532010).     

Attenuation Characteristics of Corrugated Circular Groove Waveguide

When neglecting space harmonics and higher-order slot modes, the attenuation characteristic of corrugated circular groove waveguide has been investigated. It is shown that under certain conditions, the attenuation coefficient of HE ₁₁ mode will be lower than that of dominant TE ⁽¹⁾ ₁₁ mode of circular groove waveguide with same radius.     

Investigation of the Half-Circular Helical Groove Slow-Wave Structure

As a new type all-metal slow-wave structure of the millimeter wave TWT, The helical groove has a lot of advantages: large power handling capability, large sizes, high precision and moderate bandwidth. Of the helical groove structure, the half-circular helical groove can achieve wider passband than the rectangular helical groove can do. The approximate and much simple matching method of the fields of the half-circular structure is presented in this paper. The more general expressions of the dispersion characteristic and coupling impedence, in which the fast-wave modes and slow-wave modes are considered simultaneously, are obtained. It is indicated from the results of the numerical calculation that choosing suitable dimensions of the structure and suppessing the backward wave osillation, this kind of slow-wave structure can operate over 50% hot relative bandwidth.     

A Cylindrical Waveguide Structure with Helical Grooves for High Power TWTs

In this work, the field analysis of a cylindrical interaction structure, with helical grooves, and an inner dielectric lining for possible employment in high power TWT amplifiers in the conventional slow-wave regime, is presented. The Ohmic dominance of the microwave power on the walls of this propagating circuit is deduced.     

An Efficient Iterative Procedure for Solution of Plasma Loaded Helical Waveguide Problems

The behaviour of axially-symmetric waves travelling on plasma filled screened helical coil is comprehensively studied by Anicin [J. Phys. D： Appl. Phys. 33 （2000） 1276], where all analytical expressions are derived in the full-wave theory, but the diagrams are computed in the quasistatic approximation. We use an iterative procedure to overcome this limitation. The iterative procedure is rapid and we have proven that often the first-order approximant is sufficient to improve defects which are known as immanent to the quasistatic approximation. The fixed point method appears as the natural choice for numerical treatment of formulae which could arise in a broad class of physical problems usually recognized as guided surface plasma waves.     

Design of a Rectangular to Circular Groove Waveguide Transition by Finite Element Method

A rectangular to circular groove waveguide transition is described in millimeter-wave band. The transition maintains a constant cutoff wavelength. Using the Finite Element Method, the size of the variable cross-section throughout the transition are calculated and the transition is designed.     

The Analysis of Post-Mount in W-Band Circular Groove Guide

Finite-difference time-domain (FDTD) method is used to calculate the driving-point impedance of the circular groove guide diode mount. A simple way is proposed to approximate the curvilinear metal boundary of circular groove guide. Discrete equations are obtained from the Ampere's law and Faraday's law. Perfectly matched layer (PML) is applied on the open boundary of circular groove guide. At last program is made to obtain the field components. The driving-point impedance can be achieved from the ratio of the Fourier transform of the voltage and the Fourier transform of the current. The cutoff frequency and field pattern of the dominant mode are also obtained with well agreement with the theoretical results, this verifies the validity of the FDTD program.     

Investigation of the Dielectric-Loaded, Ridged Helical Groove Slow-Wave System for the Millimeter Wave TWT

A dielectric-loaded, ridged helical groove slow-wave structure for the millimeter wave traveling wave tube is presented in this paper. The effects of the groove depth, ridge dimensions and the dielectric permitivety on the wave propagating properties and the interaction impedance are investigated in detail. From the analysis, it is indicated that for broader band amplification in a helical groove travelling wave tube, a ridged helical structure with shallow groove and loaded by dielectric with proper relative permitivety may be applied.     

The Analysis of Radial Transmission-Line in W-Band Circular Groove Guide

In this paper, finite-difference time-domain (FDTD) method is used to calculate the driving-point impedance of radial transmission-line in circular groove guide. A simple way is used to approximate the curvilinear metal boundary of circular groove guide. And perfectly matched layer (PML) is applied on the open boundary of circular groove guide. Fine-grid is used to calculate the EM fields in the radial transmission-line in which we are interest. Discretized wave equation is used to update the tangential electric field on the boundary of coarse- and fine-grid. At last, the driving-point impedances related to different diameter of the radial transmission-line are obtained from the ratio of the Fourier transform of the voltage to the Fourier transform of the current.     

Calculation of Dispersion Characteristics of a Circular Waveguide with Deep Helical Corrugation by the FDTD Method

We study the dispersion characteristics of a circular waveguide with helical corrugation, which are used in microwave amplifiers and oscillators. The results of calculations by the finite difference time domain (FDTD) method are compared with the results obtained using the perturbation theory and the experimental results. The problems of improving the calculation accuracy are considered     

A New Circular Groove Guide Analysis

Using the Fourier transform and the mode matching technique, the circular groove guide is analyzed. While deriving a series of simultaneous equations basing on boundary conditions, we get the characteristic equation of this guide structure that is strict than those before. The numerical result shows that the approach presented in this paper has a good precision.     

Mechanism Analysis of One-Dimensional Quasiperiodic Groove Drag-Reduction

Grooves arranged in one-dimensional quasiperiodic patterns are prepared by mechanical method. Drag reduction experiments are performed by R/S plus rheometer and the results show that there is a novel drag reduction effect compared with periodic grooves. An equivalent grating model is proposed to investigate the mechanism. It is found that, in comparison with periodic grating, the intensity distributes more uniform in a limited area when the coherent wave gets through quasiperiodic grating. Corresponding to the quasiperiodic grooves, the energy transfers more uniform, which could inhibit the generation of large vortices.     

Analysis of Elliptical Thin Ridged Waveguide

Elliptical waveguides and ridged waveguides have found broad applications in many microwave structures. The elliptical waveguide with double infinite thin ridges has been formulated using the mode-matching method. Exact closed-form expressions for eigenvalue problem of all TE and TM modes are presented. Numerical results suggest that the elliptical ridged waveguides have larger bandwidth than that of circular ones. Supported in part by the National Natural Science Foundation of China under Grant 60532010, and in part by the Scientific Research Foundation for the Returned Overseas Chinese Scholars under Grant 04LXJ01.     

Linear Analysis of Folded Double-Ridged Waveguide

A novel slow-wave structure (SWS), the folded double-ridged waveguide structure, is presented and its linear gain properties are investigated. The perturbed dispersion equation is derived and the small signal growth rate is calculated for dimensions of the ridge-loaded region and the parameters of the electron beam. The novel structure has potential applications in the production of high power and broad band radiation. For a cold beam, the linear theory predicts a gain of 1.1-1.27dB/period and a 3-dB small-signal gain bandwidth of 30% in W-band. A comparison between the folded double-ridged waveguide SWS and folded waveguide SWS (FWSWS) shows that with the same physical parameters, the novel SWS has an advantage over the FWSWS on the bandwidth and electron efficiency.     

基于非对称脊波导的多种聚合物弯波导性能分析

以缩短马赫-曾德尔(M-Z)电光调制器分支波导为目的,将有机聚合物非对称结构的脊波导应用于S弯波导中。采用半矢量有限差分光束传输分析法,系统地分析了不同参数下采用非对称脊波导的三种常见弯波导,即正弦弯、圆弧弯和余弦弯分支波导的TM00光场传输损耗,并与采用对称脊波导的结构相比较。研究表明,在芯层厚度h=1.5μm、脊高为0.3μm、脊宽w=4μm、分支高度G=11μm的情况下,当脊波导短边芯层平板宽度s≥2μm时,在相同传输损耗条件下,正弦弯、圆弧弯和余弦弯分支波导长度分别可减少40%、30%和25%,该结果对有机聚合物M-Z调制器中分支波导的设计具有一定的参考价值。     

硅基二氧化硅波导和SOI脊型波导应力双折射研究

采用有限元方法分析了硅基二氧化硅波导和SOI（Silicon on Insulator）脊型波导内部残留热应力引起的双折射.对于硅基二氧化硅波导,应力双折射系数的数量级为10－4,对于上包层为空气的SOI脊型波导,该系数的数量级为10－5,对于上包层为SiO2的SOI脊型波导,该系数的数量级为10－3,可见在硅基二氧化硅波导和上包层为SiO2的SOI脊型波导中产生了大的应力双折射,而在上包层为空气的SOI脊型波导中应力双折射较小.