共查询到20条相似文献,搜索用时 109 毫秒
1.
提出了一种用于Smith-Purcell效应器件的介质加载光栅慢波结构,通过研究该结构的注-波互作用过程,推导出带电子注的色散方程,并数值求解出波的线性增长率.利用色散方程,结合电磁场传播的边界条件,推导出Smith-Purcell效应振荡器工作所需的起振电流.详细研究了高频结构长度、电子注主要参数和介质相对介电常数对起振电流的影响,并与普通金属光栅结构进行了比较.结果表明:保持其他参数不变时,高频结构长度越短,起振电流越大;保持高频结构参数不变时,起振电流随电子注厚度和注-栅距离的增大而增大,随电子注电压的增大而减小;与金属光栅相比,介质的引入提高了注-波互作用的增长率,有效减小了振荡器的起振电流.理论计算结果与软件CHIPIC的模拟结果比较符合. 相似文献
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提出了一种用于Smith-Purcell器件的介质加载金属光栅周期慢波结构.通过采用本征函数法和单模近似法求解了介质加载金属光栅的"热"色散方程,在同步点得到了注-波互作用的一阶和二阶增长率,分析了光栅槽宽和槽深对色散特性的影响,并研究了电子注参数及其与光栅表面距离等主要参数对增长率特性的影响.结果表明:通过介质加载金属光栅有利于减弱色散,随着介质相对介电常数、槽宽度以及深度的增大,色散曲线变平缓且向低频区移动;当电子注参数变化时,一阶增长率曲线从整体上粗略地描述增长率变化趋势,二阶曲线则更精细地描述增长率相应值的变化.利用软件MAGIC对该结构的色散特性进行了二维模拟,模拟结果与理论计算值符合良好. 相似文献
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提出了一种介质加载折叠波导慢波结构,给出了该结构中存在电子注时慢波互作用的热色散方程,在介电常数εr=1的特殊情况下该方程即简化为普通折叠波导的小信号工作方程.在给定慢波结构尺寸的基础上,分析比较了介质加载对放大器小信号增益特性的影响,结果表明:"弱加载"(介质厚度d/a<0.1)时,无需重新设计慢波结构的参数,只需适当调整工作电压和电流就可以满足原有设计要求,而且和未加载时相比增益特性更为平坦,降低的电子注阻抗也有利于电子效率的提高.考虑到
关键词:
折叠波导
行波管放大器
介质加载
热色散方程 相似文献
4.
利用自洽线性场理论,导出了薄环形相对论电子注通过填充等离子体的介质同轴波导中的注波互作用色散方程,得到了注波互作用产生切伦科夫辐射的同步条件和波增长率。分析了填充等离子体后的波与电子注之间的能量交换及等离子体密度对色散特性、波增长率和注波能量交换的影响。分析结果表明:切伦科夫辐射是由沿介质同轴波导传播的慢波与沿薄环形相对论电子注传播的负能空间电荷波耦合所致,且其耦合强度与电子注的密度成正比;输出频率和波增长率随着填充等离子体密度的增大而提高;保持一定的输出频率,增大电子注的束流可得到高的微波输出功率。 相似文献
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提出将开槽单矩形栅和圆形电子注作为 W波段返波振荡器的注波互作用回路. 使用 3维电磁场仿真软件CST-MWS对开槽单矩形栅的高频特性进行了仿真分析, 研究结果表明: 相对于传统单矩形栅, 新结构的基模带宽有所展宽; 基模与高次模发生模式竞争的可能性很小; 在采用圆形电子注时新结构能获得大得多的耦合阻抗; 新结构的趋肤损耗略有改善. 将该慢波结构应用于设计一支以94 GHz为频带中心的W 波段返波振荡器: 设计了简洁的慢波过渡部分、输出耦合器和终端匹配衰减器, 优化参数后获得了良好的信号传输特性; 利用粒子模拟软件CST-PS对返波振荡器模型进行了三维大信号注波互作用计算, 设定合适的电子注电流等参数后, 调整工作电压在较宽的频带内获得了瓦级的功率输出, 电子效率在整个频带范围内优于1%.
关键词:
开槽单矩形栅
圆形电子注
返波振荡器
W波段 相似文献
8.
对于离散的金属柱结构构建的周期性平板慢波系统,本文利用3维FDTD方法结合HFSS仿真软件深入分析了该慢波系统的高频特性.研究了金属柱高度、周期长度对色散特性的影响,计算了耦合阻抗,并与传统光栅慢波系统特性进行了对比分析.分析表明金属柱慢波系统既有与传统光栅慢波系统相似的高频特性,又具有独自的特点,位于离散的金属柱周期间隙中的电子注互作用耦合阻抗具有对称性;金属柱结构用作真空电子器件的高频系统可增加发生有效互作用的电子注厚度,降低起振电流密度,提高器件效率.本文的分析结果为设计低电流密度工作的多电子注短毫
关键词:
金属柱平板慢波系统
3维FDTD算法
色散特性
耦合阻抗 相似文献
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本文利用自洽非线性理论对回旋速调管放大器中的电子注-波互作用进行了时域瞬态分析,建立了多腔回旋速调管非线性理论,给出了相应的电子运动方程和复数形式的互作用瞬态场方程.探讨了调制腔、中间腔、和输出腔中注-波互作用的模型和研究方法,考虑了电子速度零散对注-波互作用的影响.最后利用FORTRAN语言给出并分析了一支Kα波段四腔回旋速调管注-波互作用的数值计算结果,经与实验值和PIC模拟结果相比较,三者较为符合.
关键词:
回旋速调管
电子注-波互作用
瞬态非线性理论 相似文献
11.
Study of the Leakage Loss in a Silica-on-Silicon Slab Waveguide 总被引:1,自引:0,他引:1
A simple and efficient method for studying the leakage loss in a conventional silica-on-silicon planar waveguide is presented. The magnitude of the leakage loss is obtained by calculating the complex propagation constant of the leaky waveguide structure. The dependence of the leakage loss on the thickness of the silica buffer layer (as well as the thickness of the silica upper-cladding layer) is investigated. Numerical results are presented and compared to those calculated with the beam propagation method. 相似文献
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The method of nitriding of metals in an electron beam plasma is used to change the current density and energy of nitrogen
ions by varying the electron beam parameters (5–20 A, 60–500 eV). An electron beam is generated by an electron source based
on a self-heated hollow cathode discharge. Stainless steel 12Kh18N10T is saturated by nitrogen at 500°C for 1 h. The microhardness
is measured on transverse polished sections to obtain the dependences of the nitrided layer thickness on the ion current density
(1.6–6.2 mA/cm2), the ion energy (100–300 eV), and the nitrogen-argon mixture pressure (1–10 Pa). The layer thickness decreases by 4–5 μm
when the ion energy increases by 100 V and increases from 19 to 33 μm when the ion current density increases. The pressure
dependence of the layer thickness has a maximum. These results are in conflict with the conclusions of the theory of the limitation
of the layer thickness by ion sputtering, and the effective diffusion coefficient significantly exceeds the well-known reported
data. 相似文献
15.
采用离子束溅射技术制备了单层和双层Ge量子点, 通过原子力显微镜对比了不同Si隔离层厚度和不同掩埋量子点密度情况下表层量子点的尺寸和形貌差异, 系统研究了掩埋Ge量子点产生的应变对表层量子点的浸润层及形核的影响, 并用埋置应变模型对其进行解释. 实验结果表明, 覆盖Ge量子点的Si隔离层中分布着的应变场, 导致表层量子点浸润层厚度的降低, 从而增大点的体积; 应变强度随隔离层厚度的减小而增加, 造成表层量子点形状和尺寸的变化; 此外, 应变还调控了表层量子点的空间分布.
关键词:
Ge量子点
埋层应变
离子束溅射 相似文献
16.
We report a numerical simulation of continuous terahertz beam induced transient thermal effects on static water. The terahertz wave used in this paper has a Gaussian beam profile. Based on the transient heat conduction equation, the finite element method (FEM) is utilized to calculate the temperature distribution. The simulation results show the dynamic process of temperature change in water during terahertz irradiation. After about 300 s, the temperature reaches a steady state with a water layer thickness of 5 mm and a beam radius of 0.25 mm. The highest temperature increase is 7 K/mW approximately. This work motivates further study on the interaction between terahertz wave and bio-tissue, which has a high water content. 相似文献
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Two-dimensional thermoelasticity analysis of functionally graded thick beams is presented using the state space method coupled
with the technique of differential quadrature. Material properties vary continuously and smoothly through the beam thickness,
leading to variable coefficients in the state equation derived from the elasticity equations. Approximate laminate model is
employed to translate the state equation into the one with constant coefficients in each layer. To avoid numerical instability,
joint coupling matrices are introduced according to the continuity conditions at interfaces in the approximate model. The
differential quadrature procedure is applied to discretizing the beam in the axial direction to make easy the treatment of
arbitrary end conditions. A simply-supported beam with exponentially varying material properties is considered to validate
the present method. Numerical examples are performed to investigate the influences of relative parameters. 相似文献
18.
Jyotsna Ravi S. Lekshmi K.P.R. Nair T.M.A Rasheed 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,83(2):193-202
A modified amplitude method to analyze the photothermal probe beam deflection signal for the determination of low thermal diffusivity values of materials is proposed. This simple theoretical model, which is an extension of the amplitude method proposed by Quelin et al., takes into account the dependence of the photothermal signal on the height of the probe beam above the sample surface which affects mirage measurements when the thermal diffusivity of the coupling medium is greater than that of the sample. The present work is similar to the modification to the phase method proposed by Bertolotti et al. for determination of low thermal diffusivity. The method can be applied irrespective of whether the sample is optically transparent or optically opaque and is independent of thickness. 相似文献
19.
Vibration and dynamic stability of a traveling sandwich beam 总被引:1,自引:0,他引:1
The vibration and dynamic stability of a traveling sandwich beam are studied using the finite element method. The damping layer is assumed to be linear viscoelastic and almost incompressible. The extensional and shear moduli of the viscoelastic material are characterized by complex quantities. Complex-eigenvalue problems are solved by the state-space method, and the natural frequencies and modal loss factors of the composite beam are extracted. The effects of stiffness and thickness ratio of the viscoelastic and constrained layers on natural frequencies and modal loss factors are reported. Tension fluctuations are the dominant source of excitation in a traveling sandwich material, and the regions of dynamic instability are determined by modified Bolotin's method. Numerical results show that the constrained damping layer stabilizes the traveling sandwich beam. 相似文献
20.
Electro-mechanical response of functionally graded beams with imperfectly integrated surface piezoelectric layers 总被引:1,自引:1,他引:0
The time-dependent behavior of a simply-supported functionally graded beam bonded with piezoelectric sensors and actuators
is studied using the state-space method. The creep behavior of bonding adhesives between piezoelectric layers and beam is
characterized by a Kelvin-Voigt viscoelastic model, which is practical in a high temperature circumstance. Both the host elastic
functionally graded beam and the piezoelectric layers are orthotropic and in a state of plane stress, with the former being
inhomogeneous along the thickness direction. A laminate model is employed to approximate the host beam. Moreover, the coupling
effect between the elastic deformation and electric field in piezoelectric layers is considered. Results indicate that the
viscoelastic property of interfacial adhesives has a significant effect on the function of bonded actuators and sensors with
time elapsing. 相似文献