The cyclotron autoresonance maser with a large-orbit electron ring in a dielectric-loaded waveguide

The cyclotron autoresonace maser with a large-orbit electron ring in a dielectric-loaded waveguide has been analyzed. The stability properties are investigated self-consistently on the basis of the linearized Vlasov-Maxwell equations. The numerical results show the growth rate increases when the electron rotating ratio increases. And the dielectric liner can greatly reduce the energy of the electron beam.     

7.8GHz power generation device design using a rectangular dielectric-loaded waveguide

In this paper, we present a design where a bunched relativistic electron beam traversing inside the rectangular dielectric-loaded (DL) waveguide is used as a high power microwave generation device. Two kinds of methods of calculating the electromagnetic (EM) field excited by a bunched beam are introduced, and in the second method the calculation of EM pulse length is discussed in detail. The desired operating mode is the LSM_11 due to its strong interaction with the electron beam. For the designed 7.8~GHz operating frequency, with a 100~nC/bunch drive train of electron bunches separated by 0.769~ns, we find that high gradient (>30~MV/m) and high power (>160~MW) can be generated. An output coupler is also designed which is able to extract the generated power to standard waveguides with a 94% coupling efficiency.     

电子束空间极限电流的非线性理论研究

从电子束一维稳态传输的电势非线性Poisson方程出发,推导了圆柱波导内实心束和环形束空间极限电流与电子入射电势的依赖关系,给出了数值求解方法和解的特征,分析比较了数值计算与现有解析公式及粒子模拟的结果.考虑电子的横向运动,对数值方法进行了二维修正,计算结果与粒子模拟结果具有很好的一致性.说明利用数值方法计算电子电势非线性微分方程能够得到更精确的电子束在圆柱波导内的空间极限电流;另外,对其他形状的波导,尤其是难以得到解析式的情况,根据实际几何结构设置边界条件,数值方法可以方便地给出束流传输特性,对设计新型结构的高功率微波器件提供理论指导. 关键词： 相对论电子束 圆柱波导 空间极限电流 束流传输     

介质加载折叠波导行波管的线性分析

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ε_r=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     

介质加载矩形波导栅行波管的小信号增益计算

介质加载矩形波导栅行波管是一类新型毫米波大功率器件.给出了此结构引入电子束后的“热”色散方程,并利用“牛顿下山”法求解了此复杂系数超越方程,研究了介质加载以及电子束参数对小信号增益的影响.计算结果表明：介质加载可以扩大矩形波导栅行波管的带宽,而增益有所减小.为了弥补增益的降低,可以适当增加槽深度,也可在一定的范围内提高电子束电流.给出的结论对于研制此类行波管具有一定的指导意义. 关键词： 介质加载 矩形波导栅 小信号增益 “热”色散方程     

高功率微波在等离子体填充波导中的谐波产生

采用等离子体流体理论，研究了高功率微波在等离子体填充波导中的谐波产生，导出了非线性波动方程. 对二次谐波产生进行了数值计算与分析. 理论分析和数值计算表明，高功率微波将在等离子体填充波导中激发起谐波，TE_0n模式与TM_0n模式的基波都将激发起TM类型的谐波. 关键词： 高功率微波 谐波产生 等离子体填充波导     

箔聚焦强流相对论环形束在同轴波导中的传输

 结合箔聚焦和静电线聚焦的特点,对箔聚焦强流相对论环形电子束在同轴波导中的传输进行了研究。通过数值求解电势满足的泊松方程,得到电势、电场分布及系统的空间电荷限制流,并根据电子的运动方程得到包络电子的平衡条件及其运动轨迹。     

箔聚焦强流相对论环形束在同轴波导中的传输

结合箔聚焦和静电线聚焦的特点,对箔聚焦强流相对论环形电子束在同轴波导中的传输进行了研究。通过数值求解电势满足的泊松方程,得到电势、电场分布及系统的空间电荷限制流,并根据电子的运动方程得到包络电子的平衡条件及其运动轨迹。     

Transmission properties of microwave in rectangular waveguide through argon plasma

To study the impact of plasma generated by microwave breakdown on the propagation properties of microwave in high power microwave(HPM) devices, a three-dimensional(3-D) fluid model of argon plasma slab in rectangular waveguide is established and calculated by the finite-difference-time-domain(FDTD) method. A rectangular waveguide with a breakdown chamber filled with argon is set as the physics model, and HPM with frequency of 3–50 GHz propagates through this physics model. The time evolutions of the breakdown process are investigated, the reflection, transmission, and absorption coefficients of HPM are calculated, and the influences of some important parameters, including the thickness of the plasma slab and the microwave frequency on the propagation properties of the microwave are shown. Results of this work can offer theoretical instructions for suppressing the influence of breakdown to the performance of HPM devices, and for the use of microwave breakdown, such as the design of plasma limiter or absorber in HPM devices.     

Transition radiation of surface electromagnetic waves by electron bunches in a cylindrical waveguide

Transition surface electromagnetic radiation from electron bunches that cross a metal-insulator-semiconductor structure in a perfectly conducting semi-infinite cylindrical waveguide is studied. It is shown that, using a periodic sequence (train) of electron bunches, a particular surface waveguide eigenmode can be amplified by bringing its frequency to resonance with the bunch repetition frequency in the train. Those eigenmodes are amplified most efficiently whose frequency falls into the range occupied by the first maximum of the geometric factor of one bunch.     

Optical microwave generation using two parallel DFB lasers integrated with Y-branch waveguide coupler

A new device of two parallel distributed feedback (DFB) lasers integrated monolithically with Y-branch waveguide coupler was fabricated by means of quantum well intermixing. Optical microwave signal was generated in the Y-branch waveguide coupler through frequency beating of the two laser modes coming from two DFB laser in parallel, which had a small difference in frequency. Continuous rapid tuning of optical microwave signal from 13 to 42GHz were realized by adjusting independently the driving currents injected into the two DFB lasers.     

Excitation of microwave by an annular electron beam in a plasma-filled dielectric lined waveguide

An axial relativistic electron beam passing through a slow wave structure is unstable to an electromagnetic perturbation whose phase velocity equals the velocity of the beam. This phenomenon of Cherenkov emission is the basis of all traveling wave tubes. In this paper an excitation of Cherenkov radiation by a thin annular relativistic electron beam in a plasma-filled dielectric-lined waveguide is analysed by use of the self-consistent linear theory. The effect of the thin annular electron beam on the beam-wave interaction is completely described by a jump condition. The dispersion equation and the simultaneous condition of the beam-wave interaction are derived. Finally, the growth rate of the wave is obtained, and the effect of the background plasma density and the electron beam radius on the growth rate of the wave are presented.This work is supported by National Natural Science Foundation of China.     

Numerical analysis of radiation by a relativistic electron beampropagating parallel to a reflection grating

Two-dimensional radiation by a relativistic sheet electron beam propagating parallel to a reflection grating composed of a sinusoidally corrugated conducting surface is studied rigorously using the mode-matching method. Accurate dispersion curves for the eigenmodes that govern the Smith-Purcell radiation and the instability of the electromagnetic surface wave are presented. The imaginary parts of the eigenwavenumber and eigenfrequency give the leakage coefficient of space-charge waves and the growth rate of electromagnetic surface waves. Their dependences on the dimensions of the radiating structure are discussed. Optimum parameters for achieving the maximum leakage coefficient and the growth rate are determined. The method is general and can be applied to any two-dimensional system of electron beam coupled to an open periodic structure of arbitrary profile     

Wave growth rate in a cylindrical metal waveguide with ion-channel guiding of a relativistic electron beam

This paper addresses the formulae and numerical issues related to the possibility that fast wave may be grown when a relativistic electron beam through an ion channel in a cylindrical metal waveguide.To derive the dispersion equations of the beam-wave interaction,it solves relativistic Lorentz equation and Maxwell’s equations for appropriate boundary conditions.It has been found in this waveguide structure that the TM 0m modes are the rational operating modes of coupling between the electromagnetic modes and the betatron modes.The interaction of the dispersion curves of the electromagnetic TM 0m modes and the upper betatron modes is studied.The growth rates of the wave are obtained,and the effects of the beam radius,the beam energy,the plasma frequency,and the beam plasma frequency on the wave growth rate are numerically calculated and discussed.     

高功率微波作用下高电子迁移率晶体管的损伤机理

本文针对高电子迁移率晶体管在高功率微波注入条件下的损伤过程和机理进行了研究,借助SentaurusTCAD仿真软件建立了晶体管的二维电热模型,并仿真了高功率微波注入下的器件响应.探索了器件内部电流密度、电场强度、温度分布以及端电流随微波作用时间的变化规律.研究结果表明,当幅值为20 V,频率为14.9 GHz的微波信号由栅极注入后,器件正半周电流密度远大于负半周电流密度,而负半周电场强度高于正半周电场.在强电场和大电流的共同作用下,器件内部的升温过程同时发生在信号的正、负半周内.又因栅极下靠近源极侧既是电场最强处,也是电流最密集之处,使得温度峰值出现在该处.最后,对微波信号损伤的高电子迁移率晶体管进行表面形貌失效分析,表明仿真与实验结果符合良好.     

Photonic-crystal waveguide for the second-harmonic generation

The possibility of efficient second-harmonic generation in the optical range in a planar dielectric waveguide with the active region in the form of a one-dimensional photonic crystal has been theoretically shown. The true phase matching can be achieved by controlling wave dispersion in the photonic crystal. The dispersion equations for the photonic crystal and three-layer waveguide have been self-consistently solved. It is shown that the coherence length may exceed 10 mm.     

Periodicity-suppressing effect of periodic lossy-dielectric-loaded cylindrical waveguide

Periodic dielectric-loaded waveguide is one of the diaphragmatic waveguides.For the excellent mode-selective propagation ability,it is of value for applications in gyrotron-traveling-wave amplifiers(gyro-TWT),accelerators,and other microwave propagation systems.This paper focuses on studying the application of the strong lossy-dielectricloaded periodic waveguide in millimeter-wave gyro-TWT.It is revealed that due to the lossy property of the dielectric,the energy in the dielectric slots is absorbed effectively and the high order Bloch harmonics induced by the periodicity of the structure are suppressed,which changes the discrete spectrum under lossless condition into a continuous one.As a result,the periodicity of the system is severely suppressed and a mode in the hollow region could be approximated by a fast wave mode in an empty waveguide.These results bring specific guidance for the applications of the lossy dielectric-loaded waveguide in gyro-TWTs and other devices.     

波导管中微波波长测量方法的研究

基于微波测量线中驻波分布公式,采用测量驻波强度沿着 x轴分布的数据,拟合得到了波导管中微波的波长,不仅误差得到减小,而且可以绕过驻波比测量,用拟合参量计算微波反射率。     

横向电感膜片微波矩形波导的传输特性

以微波传输线等效二端口网络模型等效电路理论近似分析了含有横向电感膜片矩形波导的结构。计算发现,矩形波导内置一对膜片时膜片的宽度会影响散射参数的相位和振幅,而膜片放置的位置对散射参数的幅值及带宽没有影响。根据微波无反射传输的条件,研究了微波矩形波导内置两组横向电感膜片结构的转移矩阵。采用Matlab编程计算,得到在插入衰减最小时两组膜片在波导中的最佳间距。等效电路理论计算结果与用CST软件仿真的结果相符。研究发现,在膜片间距取最佳值时,两种方法得到的相对带宽差值仅为0.59%。