多注速调管双重入式谐振腔的解析计算与仿真

 发展了一种计算多注速调管双重入式谐振腔的计算方法。根据场的等效原理将（模型等效后）腔体划分为二个规则区域，每个区域上的场由公共界面上的虚设磁流所激发。利用格林函数积分法可求得各场的分布，由相邻区域公共边界场的匹配条件得到场匹配方程，从而求解出腔体谐振频率，并采用微扰法对计算数据予以修正,同时可得到腔体另一重要参数特性阻抗。另外使用HFSS软件仿真腔体，并给出计算、仿真、实测数据比较。     

X波段五腔渡越管振荡器的高频特性研究

 从麦克斯韦方程出发，采用时域有限差分的方法，对X波段五腔渡越管振荡器的谐振腔进行了高频特性研究，给出了该谐振腔中的TM₀₁模的非π模式的本征频率、Q值以及对应的场分布，并用实验冷测法测出了谐振腔的谐振频率与Q值。数值计算与实验结果比较一致，说明了该高频特性研究结果的可靠性。     

具有二维光子带隙结构的太赫兹谐振腔的谐振特性

采用数值计算方法,模拟了具有二维光子带隙结构的太赫兹频段谐振腔的谐振模式场分布,计算了这种谐振腔的品质因数,详细分析了光子晶体结构、缺陷腔几何参量对谐振特性的影响.计算得到频率落在光子晶体禁带内的单一、高阶谐振模式,且缺陷腔横向尺寸越大,谐振模式的阶数越高.这种谐振腔具有很高的品质因数,腔体的纵向长度对品质因数的影响较大.     

相对论速调管单重入谐振腔的解析分析

 推广了一种相对论速调管单重入式无栅间隙圆柱谐振腔的解析分析与计算方法 。根据场的等效原理将腔体分为三个规则的区域,每个区域中的场由界面上的磁流所产生,利用格林函数积分法可得各个区域的场分布。由两相邻区域公共界面上的场匹配条件得谐振腔的色散方程,从而解得腔体的谐振频率,同时可得腔体的特性阻抗和场分布等参数。     

多注速调管双重入式谐振腔的解析计算与仿真

发展了一种计算多注速调管双重入式谐振腔的计算方法。根据场的等效原理将（模型等效后）腔体划分为二个规则区域,每个区域上的场由公共界面上的虚设磁流所激发。利用格林函数积分法可求得各场的分布,由相邻区域公共边界场的匹配条件得到场匹配方程,从而求解出腔体谐振频率,并采用微扰法对计算数据予以修正,同时可得到腔体另一重要参数特性阻抗。另外使用HFSS软件仿真腔体,并给出计算、仿真、实测数据比较。     

同轴边加载三腔谐振腔高频特性

研究了同轴边加载三腔谐振腔的高频特性,从圆柱坐标系下的Borgnis位函数出发求解各个区域的场表达式,利用边界条件和相邻区域公共界面上的匹配条件,导出同轴边加载三腔谐振腔内角向均匀的TM模式的色散关系和各个区域场分布的解析表达式。将求得的谐振频率和数值模拟所得到的谐振频率进行了对比验证,求解所得谐振模式的频率和场分布与数值模拟的结果基本一致。     

回旋速调放大器输入谐振腔分析及数值模拟

 输入谐振腔将波导输入的高频信号转化为内腔中工作模式的驻波场，以实现对回旋电子注角向速度的调制。对输入谐振腔的同轴谐振腔和两端开孔的圆柱谐振腔分别进行了解析分析，数值计算中引入修正来反应耦合狭缝的影响，几min就能完成一种结构尺寸的计算分析。通过优化得到输入谐振腔的初步结构和尺寸，然后利用三维高频分析软件HFSS进行精确的模拟和修正，提高模式转化效率和纯度，获得了高性能的输入谐振腔。     

复合腔回旋管高频结构

为了提高回旋管的工作效率,高频结构中的模式之间的竞争是急需解决的问题。从模式耦合理论出发系统地研究了回旋管中过渡渐变复合腔的高频场结构,同时考虑了TM型寄生模式对工作模式的影响。通过对耦合系数的分析,为了降低模式之间的耦合程度,采用曲线作为回旋管中高频结构的渐变段。用三维电磁仿真软件和自主开发的程序对高频结构进行计算。计算结果与传统的线性渐变段谐振腔相比,采用非线性类型的谐振腔具有更强的模式抑制能力,并且该类型腔体中能够激励起更强的场幅值。     

复合腔回旋管高频结构

为了提高回旋管的工作效率,高频结构中的模式之间的竞争是急需解决的问题。从模式耦合理论出发系统地研究了回旋管中过渡渐变复合腔的高频场结构,同时考虑了TM型寄生模式对工作模式的影响。通过对耦合系数的分析,为了降低模式之间的耦合程度,采用曲线作为回旋管中高频结构的渐变段。用三维电磁仿真软件和自主开发的程序对高频结构进行计算。计算结果与传统的线性渐变段谐振腔相比,采用非线性类型的谐振腔具有更强的模式抑制能力,并且该类型腔体中能够激励起更强的场幅值。     

X波段相对论大功率速调管放大器的高频结构模拟研究

采用MAGIC 2.5D模拟软件,建立了X波段11.424GHz相对论大功率速调管放大器的高频结构模型。该模型由5个简单药盒型谐振腔组成,包括1个输入腔、3个中间腔和1个输出腔。研究了该模型的高频特性,初步设计漂移管及各谐振腔结构参数,再结合热腔模拟,研究了输入腔的吸收匹配问题,依据各腔体对基波电流逐级调制情况,优化配合各腔体的间隙等结构参数,从而获得电子束的最佳调制状态,最后通过调节外加均匀磁场大小获得百MW功率输出,结果表明:在加速电压520kV、束电流460A、外加磁场0.4T的条件下,当注入信号功率为1kW时,基波电流调制深度达162%,最终输出功率105MW,效率43.5%,增益50dB。     

Theoretical Analysis of Resonant Cavities Loaded with Lossy Material

Theoretical analysis of abrupt cavities loaded with lossy material has been described in detail. Dispersion equation for waveguides with lossy material and hybrid modes (HEM) matching equations for abrupt structure were derived. Further, the equations have been solved by numerical calculation to study waveguides and abrupt cavities loaded with lossy material. The theoretical analysis is available for designing and analysis RF devices. It was used to design the RF system for Ka band gyroklystron amplifier, the calculation results accord with the cold test.     

任意截面波导中截止波长测试的一种新方法

 提出了一种测试任意复杂截面波导截止波长的新方法。该方法利用波导及谐振腔的有关理论,把任意复杂截面波导的截止频率测试问题转化为对波导谐振腔的测试,因而不但在测试中回避了匹配和过渡等难题,而且达到较高精度,非常适合于微波工程设计使用。还提出了对波导衰减以及模式场分布的测试方法。     

A linear-operator formalism for bianisotropic waveguides

A bianisotropic waveguide can be defined as a cylindrical waveguide filled with bianisotropic materials, and all the conventional waveguides are special cases of the bianisotropic waveguide. In this paper, guided wave propagation in bianisotropic waveguide is analyzed by the theory of linear operators, and two types of adjoint waveguides and inner products are introduced respectively. Based on the concept of adjoint waveguides, the functional expressions of the field equations can be obtained, and from which the eigenvalue problem of the bianisotropic waveguide can be solved. Also, bi-orthogonality relations of guided modes are derived. These biorthogonality relations reported here can be used to expand electromagnetic fields in terms of a complete set of modes in straight bianisotropic waveguide. As an example of application, mode matching formulae for a discontinuity problem are given.     

Design and model of wideband absorber made of ultrathin metamaterial structures

A planar microwave ultrathin broadband absorber is proposed. It is composed of metallic patterns arranged on a dielectric material which is backed by a copper plate. The patterns of different dimensions allow to judiciously design absorption peaks at specific frequencies of interest. These peaks are due to the mode resonances of the cavities formed by the metallic patches, the dielectric substrate and the copper plate. In order to widen the absorption bandwidth, patterns of different dimensions are used, together with the different modes of these cavities. Numerical and experimental results are presented to validate the proposed method at microwave frequencies. It is also shown that the use of a composite air dielectric substrate supporting the metallic patterns helps to increase the absorption level.     

Nonperturbative solutions to cylindrical resonant cavities with dissipative medium and imperfectly conducting walls

Cylindrical waveguides without end surfaces can serve as two-dimensional resonant cavities. In such cavities the electromagnetic oscillations corresponding to an eigenfrequency can always be taken as TM or TE modes even when the walls have a finite conductivity and the medium is absorptive. This paper obtains analytic solutions to the field equations when the cylinder has a circular cross section. Some nonperturbative conclusions are drawn from the eigenvalue equation. Approximate analytic results for the resonant frequencies are obtained when the absorption of the medium is small and the walls are good conductors. Stability of the eigen modes is discussed. Similar results for the coaxial line are presented.     

Cavity mode control in side-coupled periodic waveguides: Theory and experiment

We demonstrate that the modes of coupled cavities created in periodic waveguides can depend critically on the longitudinal shift between the cavities. In the absence of such shift, the modes feature symmetric or antisymmetric profiles, and their frequency splitting generally increases as the cavities are brought closer. We show that the longitudinal shift enables flexible control over the fundamental modes, whose frequency detuning can be reduced down to zero. Our coupled-mode theory analysis reveals an intrinsic link between the mode tuning and the transformation of slow-light dispersion at the photonic band-edge. We illustrate our approach through numerical modeling of cavities created in arrays of dielectric rods, and confirm our predictions with experimental observations.     

Coupling of cavity modes and guiding modes in two-dimensional phononic crystals

Cavity modes for the single-cavity and the double-cavities in two-dimensional phononic crystal are studied by using a plane waves expansion supercell method. We show that the single-cavity behaves like an atom while the double-cavities behave like a molecule. Couplings of cavity modes with the waveguide modes are investigated for typical configurations. Suitably designed waveguides with introduced cavities might be used as acoustic filter in waveguide applications.     

基于光子晶体共振耦合的四波长波分复用/解复用器

谐振腔因其具有选频功能而在集成光学领域具有广泛的应用. 通过两个光子晶体环形腔、四个不同尺寸的光子晶体微腔及波导之间的耦合, 实现了1310 nm, 1550 nm, 1600 nm和1650 nm 四个波长的波分解复用．时域有限差分法模拟分析的结果表明, 仅仅通过调制输出波导边缘介质柱的半径, 即可使四个波长的输出效率均达到90%以上. 所设计的器件不但效率高, 而且尺寸小(约为12 μ m× 17 μ m), 在未来的光通信领域中具有潜在的应用价值.     

Circularly birefringent optical fibres: new proposals

A new family of azimuthally inhomogeneous fibres is proposed and analysed theoretically. In contrast with previous similar structures, in these fibres one can find exact analytical expressions for the guided fields. Such modes could also be used as zeroorder approximations in analysisng other waveguides.This paper presents the basic theory and several examples illustrating how the main parameters (radii, number and width of the sectors, and refractive indices) affect the field profiles. We also present introductory, qualitative arguments on how this improved control over the field could be exploited in order to get either high circular birefringence or good matching of the guided modes to TEM₀₀ or LP₀₁ exciting fields.     

Coupling constant of microcavity waveguides based on coupled mode theory

We analyze the microcavity waveguides and derive the coupling constant based on the coupled mode theory. The formula contains only two parameters with clear physical meanings, the quality factor of the cavity modes and the phase shift that the lightwave acquires when tunnelling between two cavities. It provides an easy way to express and modulate the properties of the waveguides. Our analytical results are supported by the simulations using the transfer matrix method.