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 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).     

Linear Analysis of Folded Double-Ridged Waveguide Slow-Wave Structure for Millimeter Wave Traveling Wave Tube

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 caleulated 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.     

The Millimeter Wave Radiation of a Traveling Wave Sinusoidal Wire Antenna

In this paper, investigation of radiation properties of the traveling-wave sinusoidal wire antennas is extended to the millimeter-wave frequencies (Ka-band) for the antennas whose geometrical dimensions vary in a wide range. Far-field patterns and S-parameters of composed three antenna sets were measured. A mathematical model was constructed for the structure and a MATLAB code based on this theoretical approach was written to calculate patterns, phase and attenuation constants of all investigated antennas. Frequency characteristics and the relation of antenna dimensions with wave parameters were investigated. Measured and calculated patterns were also compared with the constructed far-field patterns obtained by MoM (method of moments) and the MoM current distributions were used to explain the loss mechanisms of antennas. A directive, undistorted and smooth radiation can be achieved only choosing small undulated antennas whose peak-to-peak amplitude to period ratio κ is smaller than 0.4 (κ < 0.4). It is shown that wavelength of broadside radiation is not equal to antenna period for all antennas, except for very small undulated antennas (κ < 0.2). This antenna type can be used as a frequency-scan antenna for millimeter wave radars.

Efficient Analysis of Millimeter Wave Circuit Using Numerical Calibration Technique

In this paper, A numerical technique, called short-open calibration (SOC), in conjunction with edge-based finite element method (FEM) is employed to analyze millimeter wave circuit that can be segmented into two distinct section: static model of feedlines and dynamic model of circuit discontinuity. The derivation of reflection coefficient of 3D discontinuities is arranged in two steps. In the first step, this SOC technique is incorporated into the FEM for mesh truncation of computaional domain. In this way, much faster convergence is achieved for large-sparse linear matrix equations from FEM by this termination than by perfectly matching layers (PML). The field distribution of the dominated mode in uniform feedlines and entire circuit is obtained individually by exciting a pair of even and odd impressed voltages along the struture. In step two, Scattering parameters based on the voltages and current defintion is calculated by integral of electric and magnetic fields. Numerical solutions for a class of planar circuit discontuities are very well compared with those published in the available literatures.     

Ka波段耦合腔行波管放大器设计

由于Ka波段耦合腔行波管放大器设计技术取得了较大的发展,已经可以满足军用雷达的严格要求,这种设计技术也受到更多的关注.这里简要介绍Ka波段耦合腔行波管放大器的设计技术.通过介绍Ka波段耦合腔行波管放大器的基本组成、工作原理及设计中仿真工具的运用来说明这种设计技术.用这种设计技术成功设计出了多种耦合腔行波管放大器,在功率和体积方面突破了原有的Ka波段固态和螺旋线行波管放大器的局限,取得了明显的进步.Ka波段耦合腔行波管放大器的设计技术经过实践验证,在输出功率、带宽及重量方面已经取得了重大突破,满足了现代军用雷达的需求.     

Preliminary Design of a Harmonic-doubling Gyrotron Traveling Wave Amplifier

This study proposes a Ka-band harmonic-doubling gyrotron traveling-wave amplifier (gyro- TWT), using distributed wall losses in the input stage and mode-selective interaction circuit in the output stage, to improve the stability of the amplification. Based on a large signal simulation code, a saturated peak power of 163 kW with an efficiency of 15.5%, a gain of 31.1 dB, and a 3 dB bandwidth of 0.9 GHz is predicted for the gyro-TWT driven by 70 kV, 15 A electron beam with a velocity ratio of 1.2 and velocity spread 5% at 33.2 GHz.     

Effect of Attenuator on BWO Start Oscillation Condition in a Helix Millimeter Wave TWT Under Magnetic Focusing

In a practical helix millimeter wave traveling-wave tube (TWT), there are always magnetic focusing system for constraining the electron beam as it passes through the interaction region and attenuator for suppressing the oscillations, including backward-wave oscillation (BWO) and improving the output power. In view of the attenuator and magnetic focusing system, a 2D linear theory is employed to analyze BWO start oscillation condition. Numerical results show that the start oscillation length of the millimeter wave TWT decreases when the start position of the attenuator is close to the input section of the slow wave structure (SWS), and that it increases with the decrease of the attenuation length or the increase of the attenuation quantity. Therefore, in order to predict the BWO accurately, we should take into the attenuator and magnetic focusing system account.     

The Improvement of PML Approach for the Calculation of Microwave and Millimeter Waves Circuit

The improved PML absorbing boundary condition have been introduced in this paper. The reflection coefficient of the absorbing boundary condition is less than the reflection coefficient of Berenger's PML algorithm. And in order to validate the theory and its effectiveness, We have applied the absorbing boundary condition to the calculation of microwave and millimeter waves circuit and get its reflection coefficient S ₁₁. The numerical result is shown in this paper.     

行波管用钨铼合金中高含量铼的X射线荧光光谱测定

根据行波管用的关键材料-钨铼合金中高含量铼测定的需求,研究了用X射线荧光(XRF)光谱法测定铼时所存在的基体效应、谱线重叠和背景干扰的影响,从理论上解释了XRF二元比例法校正曲线线性差的原因。理论和实验结果均表明：直接用Re Lα分析线强度绘制的校正曲线比二元比例法可以获得更好的线性。本法具有快速准确的特点,分析结果与化学方法一致,在生产控制中应用效果显著。     

高功率窄脉冲毫米波返波管粒子模拟与实验研究

采用数值模拟方法优化设计出BWO(Backward Wave Oscillator)慢波结构, 并在RADAN303加速器平台上进行了实验研究, 在电子束电压177kV、电流785A、磁场强度1.7T的条件下, 产生毫米波辐射功率18MW、频率39.8GHz、脉冲宽度3ns、模式为TE₁₁的毫米波输出.     

Development of a Millimeter Wave Compact Equipment for NDT of Materials

We developed a compact equipment working at 94 GHz to replace the commonly used network analyzer for nondestructive testing of materials. The compact equipment was designed to measure the variations in the amplitude and phase of the reflected signal from the material relative to a reference signal. A good accuracy of the amplitude and phase measurement of the equipment was obtained in the confirmative experiments. The distribution of a drop of water in a wood plate is clearly visible in the millimeter wave images obtained by the amplitude and phase measurement.     

Theoretical Study of Millimeter Wave Harmonic Oscillator Stabilized with a Transmission Cavity

An equivalent circuit model of millimeter wave second harmonic oscillator stabilized with a transmission cavity has been proposed for constructing analytical formulations between performance parameters of the oscillator and parameters of the circuit. The model consists of an equivalent circuit of fundamental wave and that of second harmonic wave. Each of the circuits comprises circuit models of main cavity, transmission waveguide, and transmission cavity. Absorbing material placed between the transmission waveguide and the transmission cavity can suppress additional resonances originated from transmission cavity. The behavior of the second harmonic oscillator can be effectively described by the circuit model. Furthermore, based on this model, mechanical tuning characteristics have been studied at first, and then analytical formulas for quality factor and efficiency depending on circuit parameters have been derived. The circuit parameters can be conveniently extracted by electromagnetic field simulation. Hence the formulas exhibit both compact form and enough accuracy. Thereafter, general rules of performance parameters varying with circuit parameters have been deduced for the harmonic oscillators. Then some design considerations have been derived according to the corresponding analysis. The equivalent circuit model is useful for designing and adjusting millimeter wave second harmonic stabilizing oscillator with a transmission cavity.     

Modeling of Multilayer Suspended Microstrip Line and its Discontinuities on CMOS Grade Silicon Substrate for Millimeter Wave Integrated Circuit Applications

Transmission line parameters such as characteristic impedance Z₀, effective dielectric constant ε_eff, attenuation constant α of suspended microstrip line on multilayer low resistively silicon substrate are investigated using full wave FEM simulator HFSS. Effect of variation in the thickness of Si₃N_4, polyimide and metal layers on attenuation are studied. Due to suspended nature, significant reduction in transmission loss is observed in the simulation at 60 GHz frequency. Discontinuities such as open end, gap and step in width of strip conductor are analyzed to extract their lumped equivalent circuits which can be used in the design of integrated circuits.     

Traveling Wave Solutions for Nonlinear Differential-Difference Equations of Rational Types

Differential-difference equations are considered to be hybrid systems because the spatial variable n is discrete while the time t is usually kept continuous.Although a considerable amount of research has been carried out in the field of nonlinear differential-difference equations,the majority of the results deal with polynomial types.Limited research has been reported regarding such equations of rational type.In this paper we present an adaptation of the(G /G)-expansion method to solve nonlinear rational differential-difference equations.The procedure is demonstrated using two distinct equations.Our approach allows one to construct three types of exact traveling wave solutions(hyperbolic,trigonometric,and rational) by means of the simplified form of the auxiliary equation method with reduced parameters.Our analysis leads to analytic solutions in terms of topological solitons and singular periodic functions as well.     

螺旋拉胀纱线动态拉伸行为的数值模拟

螺旋拉胀纱线是由高模量纱线螺旋式包缠低模量纱线所形成的复合纱线,在纵向拉伸下呈现沿横向膨胀的负泊松比现象。为揭示其抗冲击机理,基于有限元模拟,开展了螺旋拉胀纱线的动态拉伸行为研究,发现在螺旋拉胀纱线中存在着分别由包缠纱和芯纱所主导的一快和一慢两个应力波,且在两个波阵面之间横向变形和Mises应力均随时间和空间周期性变化。给出了双波波速随加载速度和摩擦系数的变化规律,并结合等效模量的概念进行了定性讨论。模拟结果还显示,螺旋拉胀纱线中内能与动能基本相等,且摩擦对能量吸收有重要贡献。     

A Novel Parallel-Series Feeding Network of Microstrip Patch Arrays with Composite Right/Left-Handed Transmission Line for Millimeter Wave Applications*

A novel parallel-series feeding network of microstrip patch arrays with composite right/left-handed transmission line (CRLH-TL) for millimeter wave applications is proposed. Since there is no inserting phase shift in the patch elements with CRLH-TL feeding structure, the inherent pattern shift resulting from the traditional parallel-series feeding network is removed. Besides, because of the simpler structure and the shorter length of the CRLH-TL feeding network, the antenna array is of higher gain than that with the conventional parallel feeding network.* Supported by the National Natural Science Foundation of China (No. 60371010) and (No. 60471037)     

Application of Preconditioned GMRES Algorithm for Analysis of Millimeter Wave Ferrite Sphere Circulators

The generalized minimal residual (GMRES) iterative method is applied to solve such sparse large non-symmetric system of linear equations resulting from the use of edge-based finite element method. In order to speed up the convergence of GMRES, the symmetric successive overrelaxation (SSOR) preconditioning scheme is applied for the analysis of millimeter wave ferrite circulator. Consequently, this preconditioned GMRES (PGMRES) approach can reach convergence 19 times faster than GMRES. The isolation and insertion losses of millimeter wave waveguide circulator are compared with those obtained from literature.     

Application of Preconditioned GMRES Algorithm for Analysis of Millimeter Wave Ferrite Sphere Circulators

The generalized minimal residual (GMRES) iterative method is applied to solve such sparse large non-symmetric system of linear equations resulting from the use of edge-based finite element method. In order to speed up the convergence of GMRES, the symmetric successive overrelaxation (SSOR) preconditioning scheme is applied for the analysis of millimeter wave ferrite circulator. Consequently, this preconditioned GMRES (PGMRES) approach can reach convergence ten times faster than GMRES. The reflection and insertion losses of millimeter wave waveguide circulator are compared with those obtained from literature.