Three Dimension Simulation of Millimeter Wave Double Staggered Coupled Cavity Structure

After analyzed the cavity field mean method theory resolution, the software simulation method to obtain the resonance frequency, Q value and RF dispersion by MAFIA and ANSYS software is discussed for the double staggered coupled cavity Millitron structure in the millimeter-wave TWT. The resonance frequency and Q value of the single cavity is obtained and is consistent with two kind of the simulation software. Their average error is about 0.6%. The two kind of the simulation result is consistent to the design precise. The simulation method saves on the cost and time in the experiment, improve the data precise and work efficiency. The trend of the dispersion simulation result is consistent with the cavity field mean method theory result. The high end of the theory result is great contrast to that of MAFIA result. It shows that the theory adopt some hypothetical conditions, But the theory result has some instructional signification in initialization design of the novel slow wave structure.     

G波段双注折叠波导行波管的注-波互作用特性

研究了G波段双注折叠波导(FWG)TE20模的基本特性。首先计算了双注FWG TE20模的高频特性,采用等效电路法计算了色散特性;根据定义式计算了耦合阻抗,同时将二者的计算结果与HFSS仿真结果进行对比。结果显示,色散特性随频率升高差距增大,耦合阻抗随频率升高差距降低。利用电磁仿真技术(CST)粒子模拟软件对双注FWG TE20模的注-波互作用情况进行仿真,得到了慢波结构中电子轨迹以及输入输出信号频谱图,结果表明,在工作频率为205 GHz时,四段FWG的增益为34.74 dB。     

三维螺旋慢波电路的精确的冷测模拟

利用MAFIA的准周期边界条件对螺旋慢波电路的高频特性进行模拟,发现模拟结果在一定的网格取值范围内作微小变化,在此基础上使得色散曲线趋于数值收敛;并提出利用MAFIA后处理模块直接计算耦合阻抗的方法;将模拟计算结果与实验测试值进行比较,其平均误差范围达到设计要求,为软件模拟的精确计算作了一些有益的研究.     

A slow wave structure for gyro-TWA H11 operation

It was shown in a previous work, that it is possible to achieve high quality amplifier application based on the basic cyclotron maser instability principle: the narrow bandwidth of gyro amplifiers could be overcome using a disc loaded circuit in the hybrid mode interaction. In this work, we use the Galerkin method to analyze the fold circuit structure, obtaining both its dispersion characteristics and its characteristic impedance. This effort complements an earlier effort, where a polynomial obtained from experimental data was used for the cold circuit dispersion characteristic. The complete behavior of the actual structure is studied: first, the propagation of the hybrid H₁₁ mode in the cold circuit; next, the finite length of the real structure is taken into account to derive the characteristic impedance of the actual circuit. Numerical and experimental results are compared and shown to match accurately throughout the wide frequency range used     

苜蓿叶形耦合腔慢波结构的模拟和验证

苜蓿叶形耦合腔慢波结构是一种高耦合阻抗的慢波线。由于结构复杂,其数学分析及工程设计都非常困难。该文利用三维电磁计算软件Isfel3d,Mafia,HFSS对这种结构的色散特性、耦合阻抗进行数值模拟,在分析模拟结果的基础上,对这种结构做了初步的优化。结果表明,数值模拟与实验结果有很好的一致性,这对改进这种慢波线的工程设计具有重要意义。     

Slow-Wave Characteristics of a Frame–Rod Structure Based on Micro-Fabricated Technology for THz Vacuum Electron Devices

A simple equivalent circuit analysis of the frame–rod slow-wave structure (SWS) on dielectric substrates of a traveling-wave tube (TWT) is developed, using the quasi-TEM approximation approach for the dispersion and coupling impedance characteristics of the structure. Moreover, the obtained complex dispersion equation and coupling impedance are numerically calculated. The calculation results by our theory method agree well with the results obtained by the 3D EM simulation software HFSS. It is shown that the dispersion of the frame–rod circuit is decreased; the phase velocity is reduced and the bandwidth becomes greater, while the coupling impedance decreases after filling the dielectric materials in the frame–rod SWS. In addition, a comparison of slow-wave characteristics of this structure with a rectangular helix counterpart is made. As a planar slow-wave structure, this structure has potential applications in compact TWTs based on the micro-fabrication technology, which could be scaled to millimeter wave, even to THz frequency.     

Suspended Broadside-Coupled Slot Line with Overlay

This paper presents a rigorous analysis of symmetric, broad-side-coupled slot line with overlay. The structure is assumed to be suspended inside a conducting enclosure of arbitrary dimensions. The dielectric substrate and the overlay are assumed to be isotropic and homogeneous and are of arbitrary thickness and relative permittivity. The conducting enclosure and the zero thickness metallization on the substrate are assumed to have infinite conductivity. The computed results illustrate a) the dispersion characteristics and characteristic impedance of the coupled slot line structure, b) the variation of the even-mode and also the odd-mode relative wavelength ratio and characteristic impedance with slot width, and c) the effect of shielding on the even-mode and also the odd-mode dispersion and characteristic impedance. This structure should find application in the design and fabrication of MIC components such as magic-T's and directional couplers.     

太赫兹折叠波导慢波结构的设计与微加工

从行波管工作的物理特性提出了一种获得折叠波导慢波结构参数的简单方法,给定工作频率和电压,能够获得折叠波导慢波结构的初始参数.设计了D波段的折叠波导结构来验证该方法,对其冷测特性如色散、耦合阻抗进行了分析.仿真结果表明,设计的折叠波导慢波结构在中心频率处具有较平缓的色散关系,在中心频率处耦合阻抗为3.5欧姆.在电子注电压为20.6 kV,电流为15 mA时,27 mm(50个周期)的折叠波导慢波结构在220 GHz具有13.5 dB的增益,3 dB带宽为11 GHz(213~224 GHz).同时讨论了折叠波导慢波结构的微加工工艺,并通过UV-LIGA工艺获得了实验样品.     

Surface waves above a trapezoidal corrugated surface

The dispersion characteristics of surface waves above a perfectly conducting trapezoidal corrugated surface are analyzed as functions of the shape and period of corrugation. The analysis is based on the impedance approximation and numerical simulation with the use of the finite-element method. For two extreme particular cases, rectangular and triangular shapes of corrugation, the values of the calculated slowing factor are compared with the results obtained from analytic formulas and from a numerical experiment.     

Investigation of Double-groove Loaded Folded-Waveguide Slow-wave Structure for Millimeter Traveling-wave Tubes

To enhance the strength of beam-wave interaction and improve the performance of gain, the double-groove loaded folded-waveguide slow-wave structure (SWS) is proposed for millimeter traveling-wave tubes (TWTs). In the first part, the expressions for the dispersion and the interaction impedance of this novel structure are obtained by using matching conditions of the RF fields. Ansoft HFSS is also used to calculate the high frequency characteristics. The simulation results from HFSS agree with the theoretical results. Numerical calculation for different combinations of the groove width and depth is carried out to study the influence of groove loading on the properties of this novel circuit. In the second part, a linear theory of a double-groove loaded folded-waveguide TWT is developed and calculated for analyzing the effect of groove dimensions on the property of small signal gain. The investigation results indicate that the interaction impedance is obviously raised up and the small signal gain are enhanced by loading groove in the FWSWS.     

螺旋慢波系统高频特性的计算机仿真

介绍了用德国CST(Computer Simulation Technology)公司提供的微波工作室MWS(Microwave Studio)4．2软件模拟计算螺旋线慢波系统的色散特性和耦合阻抗的理论方法。通过对矩形夹持杆支撑螺旋慢波结构的模拟计算,与测试结果相比色散特性的平均模拟误差为1．5%左右,耦合阻抗的平均误差为0．3％左右;相比于MAFIA仿真,计算精度更高,计算时间更短。     

A capacitively coupled meander line for solid-state traveling-wave amplification

A slow-wave structure intended for use in solid-state traveling-wave amplifiers is described. The structure is a meander line with adjacent conducting elements electrically connected by lumped capacitors. The dispersion curve is derived and shown to agree with experiment. The structure is found to have a passband which is dependent on the coupling capacitors. The interaction impedance is estimated.     

Analysis of a Disc-Loaded Circular Waveguide for Interaction Impedance of a Gyrotron Amplifier

A rigorous electromagnetic analysis of a circular waveguide loaded with axially periodic annular discs was developed in the fast-wave regime, considering finite axial disc thickness and taking into account the effect of higher order space harmonics in the disc-free region and higher order modal harmonics in the disc-occupied region of the structure. The quality of the disc-loaded circular waveguide was evaluated with respect to its azimuthal interaction impedance that has relevance to the gain of a gyrotron millimeter-wave amplifier (gyro-traveling-wave tube) in which such a loaded waveguide finds application as a wideband interaction structure. The results of electromagnetic analysis of the structure with respect to both the dispersion and azimuthal interaction impedance characteristics were validated against the commercially available code: high frequency structure simulator (HFSS). The analysis predicts that the value of the interaction impedance at a given frequency decreases with the increase of the disc hole radius and disc periodicity. The change of the axial disc thickness does not significantly change the value of the interaction impedance though it shifts the frequency range over which appreciable interaction impedance is obtained. Out of the three disc parameters, namely the disc hole radius, thickness and periodicity, the lattermost is most effective in controlling the value of the azimuthal interaction impedance. However, the passband of frequencies and the center frequency of the passband both decrease with the increase of the disc periodicity. Moreover, the disc periodicity that provides large azimuthal interaction impedance would in general be different from that giving the desired dispersion shape for wideband interaction in a gyro-TWT, suggesting a trade-off in the value of the disc periodicity to be chosen.     

一种新型微带曲折线慢波结构的设计

设计了一种新型微带曲折线慢波结构,该结构采用双介质杆支撑式的V型平面曲折线慢波电路。利用电磁场仿真软件HFSS对这种新型结构和传统微带曲折线慢波结构进行了分析比较,研究结果表明,新型微带曲折线慢波结构在不改变色散强弱的情况下,工作频段向高频端拓展且耦合阻抗有了很大提高,可以更好地工作在短毫米波段。并仿真分析了结构参数对高频特性的影响,所获得的仿真结果为器件的粒子模拟及计算慢波结构的工作效率奠定了基础。     

Parametric Simulation and Optimization of Cold-test Properties for a 220 GHz Broadband Folded Waveguide Traveling-wave Tube

Characterized with full-metal structure, high output power and broad bandwidth, microfabricated folded waveguide is considered as a robust slow-wave structure for millimeter wave traveling-wave tubes. In this paper, cold-test (without considering the real electron beam) properties were studied and optimized by 3D simulation on slow-wave structure, for designing a 220 GHz folded waveguide traveling-wave tube. The parametric analysis on cold-test properties, i.e., phase velocity, beam-wave interaction impedance and cold circuit attenuation, were conducted in half-period circuit with high frequency structure simulator, assisted by analytical model and equivalent circuit model. Through detailed parametric analyses, interference between specified structural parameters is found on determining beam-wave interaction impedance. A discretized matrix optimization for interaction impedance was effectively carried out to overcome the interference. A range of structural parameters with optimized interaction impedance distributions were obtained. Based on the optimized results, a broadband folded waveguide with cold pass-band of about 80 GHz, flat phase velocity dispersion and fairly high interaction impedance was designed for a 220 GHz central frequency traveling-wave tube. A three-dB bandwidth of 20.5 GHz and a maximum gain of 21.2 dB were predicted by small signal analysis for a 28 mm-long lossy circuit.     

A New Approach for the Analysis of Planar Distributed Two-Dimentional (2-D) Left-Haned (Lh) Structures

A new approach is proposed to analyze planar distributed 2-D LH structures. The 4-port S parameters of the unit cell combined with the Bloch-Floquet theory are used to determine the dispersion relations and Bloch impedance. The LH and RH frequency bands are identified by the signs of the real parts of the wave number and the Bloch impedance. Several advantages of the new approach over the previous unit cell analysis methods are presented. As an example, a capacitance-enhanced LH structure is designed and analyzed with the new approach. FDTD simulation is also performed to study the periodic LH structure with infinite arrays. The results of the simulation at the LH frequency band show the backward wave properties in consistent with those obtained by the proposed approach.     

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。     

Analysis of a U-shaped vane-loaded helical slow-wave structure for wideband travelling-wave tubes

The dispersion equation and interaction impedance of a U-shaped vane-loaded helical slow-wave structure (SWS) is obtained by considering the azimuthal space harmonic in the non-vane region and the helical tape thickness, using the field theory matching method in the azimuthal field discontinuity. The theoretical calculation by electromagnetic analysis is consistent with the simulation result by MAFIA, which can explain some physical essence of the SWS. In the helical SWS, negative dispersion is reported to reduce the second harmonic content of a wideband travelling-wave tube at the low-frequency end of the band. When the SWS is assembled, the support rods are easily located in the groove of the vane. The solution provides a new instruction method for other types of vane-loaded helical SWS.     

0.14 THz折叠波导行波管慢波结构设计与加工

使用一种显式方法对0.14 THz折叠波导行波管慢波结构进行了快速设计,并通过解析模型、等效电路模型以及电磁场仿真软件(CST MWS)对结构的色散关系和耦合阻抗进行了计算。计算结果表明,0.14 THz附近的色散较为平坦,耦合阻抗在1Ω左右。为了满足大功率输出需求,对初始结构尺寸进行了部分调整。CST PS互作用模拟结果表明,在0.14 THz附近,输出功率大于1 W。用微电火花(EDM)和微铣削方法分别进行了加工实验,结果表明,两种方法在尺寸精确度上均能满足指标要求,微铣削加工能获得更平整、表面粗糙度更好的槽底。     

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.