Nonuniform Layer Model of a Millimeter-Wave Phase Shifter (Comments)

In the above paper, Butler et al. have investigated theoretically the propagation characteristics of the dielectric waveguide with plasma layer created by an exponentially absorbed optical beam. They have solved numerically the complex wave equation by using a multipoint boundary-value differential equation solver. On the other hand, we have already treated the same nonuniform layer model by using a multilayer staircase method [2]. In this approach, the actual permittivity profile of the waveguide is approximated by the finite number of steps. The wave equation is solved for each step and the complex propagation constant is determined so as to satisfy the boundary conditions at all interfaces. The mathematical formulation is very simple and an accurate solution can be obtained by increasing the number of steps M. The details of the method can be found in [3] and [4].     

基于数值射线追踪的短波电离层传播轨迹研究

从电波传播的射线方程出发,在不考虑地磁场和碰撞的条件下,推导出了球坐标系下描述短波在电离层传输的轨迹方程.以准抛物电子密度模型为例,给出了求解参数方程组的初始条件.采用改进Euler数值方法求解轨迹参数方程组,得到短波轨迹的参数,实现了短波在电离层中的轨迹计算及仿真.仿真结果结果表明,用数值射线追踪法研究短波在电离层中的传播可以为短波天波通信的轨迹模拟和参数优选提供参考.     

非傍轴光束级数修正解的有效性

当光束具有较大的发散角或光束束腰可与波长相比拟时，傍轴近似不再成立。需要发展更为严格的非傍轴处理方法。迄今已提出许多方法．例如微扰法、级数展开法、算子法、角谱分析法和波动方程积分解等方法，用以研究光束的非傍轴传输行为。不同方法具有各自的优缺点和适用范围。分析了非傍轴光束级数解的有效性。对波动方程积分解和级数解作了详细的数值计算和比较，指出当ω0≤0．2251λ时(ω0为束腰宽度，λ为波长)，级数解对傍轴解有修正作用。但是，当ω0≤0．2251λ时，级数解会给出无意义的结果，并且会发散。级数解必须在其有效范围内使用。级数解的适用范围与光束的束腰宽度、传输距离以及所使用的级数解的阶次有关。     

关于衍射与无衍射光束

分析了衍射与无衍射光束的特点,讨论了无衍射光束的判据,指出衍射实质上是波动方程的非本征解光束在传输过程中趋于本征解光束的特点。     

Analysis of a large-orbit gyrotron in a coaxial waveguide underassistant background fields

The dispersion relation of a large-orbit gyrotron in a coaxial waveguide excited in the transverse-electric mode was developed starting from the beam-present wave equation. The relativistic Vlasov's equation was solved under tenuous beam approximations for the perturbed electron distribution function, hence the required current density to be used in the wave equation was found. The analysis was generalized, with respect to background fields, by considering a dc radial electric field and a dc azimuthal magnetic field, over and above conventional dc axial magnetic field. The dispersion relation was solved for the complex frequency for a given propagation constant and the imaginary part interpreted for the growth rate as well as the saturated efficiency of the device. Similarly, for a given frequency the dispersion relation was solved for the complex propagation constant and the imaginary part interpreted for the gain of the device, if configured as an amplifier. Two peaks were obtained in the gain-frequency response corresponding to two points of intersection between the beam-mode dispersion line and the waveguide-mode dispersion curve. The improvement in the growth rate, gain and saturated efficiency was predicted by the application of the additional background fields. A redistribution of beam kinetic energy between the axial and transverse electron velocities led to a remarkable enhanced saturated efficiency at the second peak. A detailed study of the variation of device performance with respect to the gain and saturated efficiency was presented, for a wide range of the dc background field and electron kinetic energy distribution parameters     

窄带和宽带双曲正割脉冲光束的解析传输式

从近轴波动方程出发推导了窄带和宽带双曲正割脉冲光束的解析传输公式。通过数值计算比较了分别采用复振幅包络(CAE)表示式和复解析信号(CAS)表示式得到的脉冲光束，得出了选择脉冲光束研究方法的条件。结果表明复振幅包络表示式得到的解会存在空间奇异性，使光束出现不符合物理意义的非光束行为。对于宽带光束，复振幅包络解的奇异点的位置距离轴中心较近，使复包络解不能正确表示脉冲光束，而对于奇异点位置远离轴中心的窄带光束，对脉冲光束产生的影响可以忽略。因此，窄带脉冲光束可以采用复振幅包络和复解析信号两种表示式来研究，而对于宽带脉冲光束，必须采用严格的复解析信号表示式。     

Propagation of Waves through Magnetoplasrna Slab Within a Parallel-Plate Guide

By applying the variational equation is established for handling wave reaction theory, a variational propagation in a parallel-plate guide within which a magnetized inhomogeneous lossy plasma slab is inserted. The equation is then solved by the finite-element method along with the frontal solution algorithm. With such an approach, the reflection coefficient and the field distribution in the slab are obtained. In this study, the factors which may influence the propagation characteristics of the guide are studied. These factors include the plasma electron density, the strength and the direction of the static magnetic field, the width and the thickness of the slab, and the electron collision Iosses. A special modal expansion solution is also incorporated to investigate an anomalous numerical instability associated with the present numerical algorithm.     

Antenna and wave theories of infinite yagi-uda arrays

An integral equation for the propagation constant along an infinitely long Yagi structure is derived by expanding the vector potential function for such an array in terms of the spatial harmonic solutions of wave theory. This equation is shown to be identical with the integral equation derived on the basis of array theory and transformed by the Poisson summation formula. With the identity of array theory and this new wave theory formation established, the wave theory is used to discuss allowed wave solutions and the physical characteristics required of dipoles in order that they support a wave solution. The fundamental integral equation is solved by means of the array theory of King and Sandler; the numerical results are found to agree quite well with previously published data. Finally, the problem of two parallel nonstaggered Yagi arrays is considered, and it is shown that the propagation constant of the composite structure either decreases or increases over that of the isolated array depending upon whether the symmetric or the antisymmetric mode is excited. Some peculiar effects are noted with respect to this antisymmetric solution, and these lead to the existence of conditions under which no unattenuated wave solution is possible. This is referred to as the "cutoff condition." Numerical results are achieved which agree very well with experimental data obtained as part of this research.     

均匀随机媒质中传播的波——有不同波数的m-n阶矩方程的解

在研究随机媒质中传播的波的一些有关问题时,常常需要求解波的矩方程。具有不同波数的m-n阶矩方程是一个抛物近似的偏微分波动方程。本文应用格林函数方法将偏微分方程变为积分方程,并用迭代法求得了该积分方程的解。同时,又应用接连散射的方法求解了具有不同波数的m-n阶矩方程,两种方法所得的结果完全相同。文中对解的物理含义作了说明,并讨论了用于波传播研究中的一些问题。     

等离子体圆柱波导慢电磁波的激励

本文在考虑等离子体厚度效应的情况上,详尽地推导了充填圆环状等离子体的圓柱波导中TM模慢电磁波的色散方程;利用相对论空间电荷波理论,导出了相对论电子注在轴向磁场引导下沿等离子体内表面传输时的空间电荷波方程;求得了电子注和慢空间电荷波相互作用的线性增益和频率漂移;讨论了等离子体厚度、密度对色散特性和互作用增益的影响。     

基于抛物方程的短波电离层传播数值模拟研究

短波电离层传播损耗的计算对电离层基础研究与短波通信、天波超视距雷达等应用有重要意义，以往主要采用半经验模型.文中基于电磁波传播的抛物方程方法，实现对短波电离层传播损耗空间分布的数值计算，该方法可同时考虑电磁波传播的折射、反射、绕射和吸收等效应.根据电子浓度剖面数据，仿真计算了不同频点和天线波束宽度情况下的电离层传播损耗，从折射效应引起的传播模式、反射点高度、地面落区位置方面，与射线描迹结果进行对比，两者具有一致性.此外，进一步仿真分析了电离层的吸收效应.研究结果初步表明了抛物方程方法预测电离层传播的有效性及其强大的功能.     

Field theory of dielectric Cherenkov maser

The effect of three-dimensional perturbed velocity and three-dimensional perturbed current density on the beam-wave interaction of dielectric Cherenkov maser is analysed by use of the self-consistent linear field theory. Three distinct cases are considered. First, the propagation of the electron beam in an annular dielectric liner enclosed by a loss-free conducting wall is investigated. The dispersion equation and the simultaneous condition of the beam-wave interaction are derived. It's clearly shown that the instability of the interaction results from the coupling of the TM mode in the dielectric lined slow-wave waveguide to the beam mode via the electron beam. And the coupling is proportional to the density of the beam. The growth rate of the wave produced by the electron beam are obtained. Then, the case of a relativistic electron beam guided by a longitudinal magnetic field in the same slow-wave structure is examined. The motion of electrons could be approximated to be one-dimensional when the simultaneous condition of the beam-wave interaction of dielectric Cherenkov maser is satisfied. Finally, the effect of the background plasma on the instability of the beam-wave interaction is studied.     

Propagation of soliton waves in nonlinear dielectric slab waveguides of parabolic index of refraction

The pulse propagation in a non-linear slab waveguide of parabolic index of refraction is treated by using differential equation techniques. A graded index dielectric slab waveguide free of material dispersion with a cubic order non-linearity is considered. The electromagnetic wave inside the waveguide is described in terms of a non-linear equation. Slowly varying envelope function representation is employed to develop a non-linear partial differential equation for the unknown envelope function of the electric field. An averaging method over the transverse direction is applied to reduce the unknown envelope function non-linear differential equation into a form resembling the well known non-linear Schrödinger differential equation. This equation is solved by applying the Inverse Scattering Method. The N-soliton solution is developed and presented explicitly for the practical case of the single mode dielectric slab waveguide. Numerical results presenting single and double soliton propagation are also given.     

强非局域介质中高斯光束参量演化规律的分析

光束存非局域非线性介质中传输时遵循非局域非线性薛定谔方程（NNLSE）。对应用变分法得到的傍轴高斯光束存强非局域非线性介质中的束宽演化方程进行了简化，消除了由于强非局域非线性介质响应函数作泰勒级数展开产生的势函数假根的影响；求出了傍轴高斯光束各参量的演化表达式。结果表明，傍轴高斯光求存强非局域非线性介质中传输时束宽的近似演化规律为正弦函数和余弦函数，并存在一个临界功率。当初始功率等于临界功率时，可以得到空间光孤子。对于一般情形，束宽作周期性压缩或展宽变化。当束宽比α≤0．3时，所得结果与非局域非线性薛定谔方程的数值解基本一致。     

均匀随机媒质中传播的波有不同波数的m-n阶矩方程的解

在研究随机媒质中传播的波的一些有关问题时,常常需要求解波的矩方程。具有不同波数的m-n阶矩方程是一个抛物近似的偏微分波动方程。本文应用格林函数方法将偏微分方程变为积分方程,并用迭代法求得了该积分方程的解。同时,又应用接连散射的方法求解了具有不同波数的m-n阶矩方程,两种方法所得的结果完全相同。文中对解的物理含义作了说明,并讨论了用于波传播研究中的一些问题。     

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.     

Analysis of coupled-structure traveling-wave tubes

Until now there has been no general method available for taking into account the effect of the electron beam on coupled-structure couplers and attenuators for traveling-wave tubes. This paper presents an analytical procedure for this purpose based on the coupled mode approach of S. E. Miller and J. R. Pierce. It is valid for loosely coupled structures with small loss, only one of which is coupled directly to the beam. In addition to other relations, a general root equation is developed which takes into account loss in either or both of the coupled structures, space charge in the beam, and the possibility of different phase velocities in each structure. Typical plots of the incremental wave parameters are shown. An experimental verification of the theory is presented that shows that predictions made by means of it will be fair to good.     

A new finite-difference-based method for wide-angle beam propagation

A novel split-step finite-difference method for wide-angle beam propagation is presented. The formulation allows solution of the second-order scalar wave equation without having to make the slowly varying envelope and one-way propagation approximations. The method is highly accurate and numerically efficient requiring only simple matrix multiplication for propagation.     

电子束被激光行波散射的相对论性经典理论

在电子间相互作用和电子辐射可忽略的条件下,得到电子束被激光行波散射的洛仑兹力方程的严格解;相对论性经典理论预言的角分布可与实验比较。     

Propagation of ELF waves below an inhomogeneous anisotropic ionosphere

The ionospheric anisotropy is considered with horizontal magnetic field either for transverse (East-West or West-East) or for longitudinal (South-North) propagation. For transverse propagation in a vertically stratified medium the differential equations of the various field components are uncoupled and a closed form solution is given for identical exponential height variation of the components of tensor conductivity. For arbitrary height variation of the tensor conductivity numerical solutions are obtained after expressing the surface impedance below the ionosphere in terms of a Riccati-type differential equation. The West-East direction of propagation exhibits a lower attenuation constant than the East-West direction forf < 1000cps. This is contrary to the expectations based on a model of a homogeneous anisotropic ionosphere. For longitudinal propagation the differential equations of the various field components are coupled, with the coupling being particularly strong above theDregion. The differential equations are simplified by assuming no coupling in the lower ionosphere and strong coupling above a pre-selected altitudey_{1}. For exponential height variation of the tensor conductivity components the closed form solution differs negligibly from the isotropic case. For arbitrary height varition of the tensor conductivity numerical solutions are obtained similarly as for the transverse propagation. Over most of the frequency range the attenuation figures for South-North propagation are intermediate between the corresponding figures for West-East and East-West propagation.