Equivalent Circuit Analysis of Serpentine Folded-waveguide Slow-wave Structures for Millimeter-wave Traveling-wave Tubes

A simple equivalent circuit model for the analysis of dispersion and interaction impedance characteristics of serpentine folded-waveguide slow-wave structure was developed by considering the straight and curved portions of structure supporting the dominant TE ₁₀-mode of the rectangular waveguide. Expressions for the lumped capacitance and inductance per period of the slow-wave structure were derived in terms of the physical dimensions of the structure, incorporating the effects of the beam-hole in the lumped parameters. The lumped parameters were subsequently interpreted for obtaining the dispersion and interaction impedance characteristics of the structure. The analysis was simple yet accurate in predicting the dispersion and interaction impedance behaviour at millimeter-wave frequencies. The analysis was benchmarked against measurement as well as with 3D electromagnetic modeling using MAFIA for two typical slow-wave structures (one at the Ka-band and the other at the W-band) and close agreement observed.     

A simple equivalent circuit analysis of rectangular folded-waveguide slow-wave structure

A simple yet accurate equivalent circuit model was developed for the analysis of slow-wave properties (dispersion and interaction impedance characteristics) of a rectangular folded-waveguide slow-wave structure. Present formulation includes the effects of the presence of beam-hole in the circuit, which were ignored in existing approaches. The analysis was benchmarked against measurement as well as with 3D electromagnetic modeling using MAFIA for two typical slow-wave structures operating in Ka- and Q-bands, and close agreements were observed. The analysis was extended for demonstrating the effect of the variation of beam-hole radius on the RF interaction efficiency of the device.     

Design and Characterization of a W-Band Folded-Waveguide Slow-Wave Structure

A single-section slow-wave structure for a W-band folded-waveguide traveling-wave tube with operating bandwidth of around 4% was designed for delivering the output power of 50 W at the operating voltage of 13.5 kV and operating beam current of 80 mA. The design was carried out using analytical formulations and 3D electromagnetic simulations. The beam-wave interaction analysis was carried out using large signal Lagrangian analysis and particle-in-cell simulation. The folded-waveguide slow-wave structure along with input-output couplers and RF windows were fabricated. Cold test measurements were carried out for dispersion characteristics of the slow-wave structure and voltage standing-wave ratio and insertion loss characteristics of the RF window. The measured cold circuit parameters show close agreement with the analysis.     

Analysis of Helix Slow Wave Structure for High Efficiency Space TWT

This paper describes the analysis of helix slow-wave structure (SWS) for a high efficiency space traveling wave tube that is carried out using Ansoft HFSS and CST microwave studio, which is a 3D electromagnetic field simulators. Two approaches of simulating the dispersion and impedance characteristics of the helix slow wave structure have been discussed and compared with measured results. The dispersion characteristic gives the information about axial propagation constant (Beta). Which in turn yields the phase velocity at a particular frequency. The dispersion and impedance characteristics can be used in finding the pertinent design parameters of the helix slow-wave structure. Therefore a new trend has been initiated at CEERI to use Ansoft HFSS code to analysis of the helix slow wave structure in its real environment. The analysis of the helix SWS for Ku-band 140W space TWT has been carried out and compared with experimental results, and found is close agreement.     

微机械圆盘谐振器的仿真分析及等效电路

通过对径向振动圆盘的机械振动方程进行分析,将机械振动的分散参数集总化,提取出机械集总参量并通过机电类比的方法将集总化的机械参量类比成电参量,建立起径向振动微机械谐振器的电参数模型。利用ANSYS软件对径向振动盘式微机械谐振器进行模拟,提取出谐振频率和振动位移,并以此为基础计算出等效质量及阻尼和刚度的数值,进而通过机电耦合系数求出电参数值。以所提取的电参数为依据,分析了谐振器的结构对谐振器的等效阻抗的影响。谐振器的等效电路及分析结果将成为后续结构和驱动电路设计的出发点。     

Traveling-wave tube gain fluctuations with frequency

Periodic traveling-wave tube gain fluctuations with frequency are described in terms of fundamental tube parameters and readily measurable quantities using the simplified one-wave theory of Pierce. An analysis of the feedback existing in a traveling-wave amplifier due to mismatches in the discontinuity regions is presented. Thus, the form, periodicity, and magnitude of these fluctuations and their dependence upon the beam voltage are quantitatively determined. The microwave structure is analyzed from a network point of view and the circuit parameters are defined with mismatches in the lumped center attenuator and at the ends of the slow-wave transmission line. The gain fluctuations are related to the cold circuit parameters and standing wave measurements. Pertinent experimental data, indicating the correlation of gain fluctuations to vswr variations, are included, in addition to an elementary discussion of the distortion effects possible due to such periodic gain variations in a traveling-wave tube.     

平面人工传输线等效集总参数经验公式的研究

平面人工传输线是一款性能良好的新型慢波结构,主要由弯曲线电感、交指电容等微带准集总元件构成。系统研究了弯曲线电感和交指电容的等效集总参数随结构参数变化的规律并给出反映这些规律的经验公式,考虑微带介质基板厚度和介电常数的影响,将所得经验公式进行修正使之适用于不同介质基板厚度和介电常数的情况,将修正的经验公式应用于基于平面人工传输线的威尔金森功分器的设计中。所得经验公式可用来快速、准确地设计平面人工传输线,对其他微带不连续或慢波结构的设计也具有参考意义。     

A Simple and Accurate Analysis of Conductivity Loss in Millimeter-Wave Helical Slow-Wave Structures

Electromagnetic field analysis of a helix slow-wave structure was carried out and a closed form expression was derived for the inductance per unit length of the transmission-line equivalent circuit of the structure, taking into account the actual helix tape dimensions and surface current on the helix over the actual metallic area of the tape. The expression of the inductance per unit length, thus obtained, was used for estimating the increment in the inductance per unit length caused due to penetration of the magnetic flux into the conducting surfaces following Wheeler’s incremental inductance rule, which was subsequently interpreted for the attenuation constant of the propagating structure. The analysis was computationally simple and accurate, and accrues the accuracy of 3D electromagnetic analysis by allowing the use of dispersion characteristics obtainable from any standard electromagnetic modeling. The approach was benchmarked against measurement for two practical structures, and excellent agreement was observed. The analysis was subsequently applied to demonstrate the effects of conductivity on the attenuation constant of a typical broadband millimeter-wave helical slow-wave structure with respect to helix materials and copper plating on the helix, surface finish of the helix, dielectric loading effect and effect of high temperature operation – a comparative study of various such aspects are covered.     

人工传输线传输特性的分析与设计

人工传输线以其慢波效应可以使微波部件小型化,因而得到了广泛应用。首先介绍了人工传输线的基本原理,给出了一种简洁的等效电路模型,然后推导出了基于该模型的传输特性计算公式;在此基础上,根据仿真结果推算出各等效电路参数,从而得到了人工传输线传输特性与等效电路参数的关系;最后设计制作了人工传输线,测试结果与分析结果比较吻合,证明了提出的分析模型是有效的。为进一步简化设计平面型人工传输线奠定了基础。     

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...