Finite Element Analysis of the TE Modes in Truncated-Circular Waveguide

Truncated-circular waveguide are used in some microwave and millimeter-wave components. The field patterns in truncated-circular waveguide are desired but usually difficult to be computed by conventional methods. In this paper, they are efficiently determined by using finite element method. The electrical field lines of the dominant TE mode and the first sixteen higher-order TE modes are presented. The calculated results in this paper have important values for us to understand the transmission characteristics of truncated-circular waveguide, and will be of practical significance in designing waveguide components in microwave and millimeter wave engineering.     

Finite Element Analysis of the Field Patterns in Elliptical Waveguide

In this paper, finite element method is first used to discuss the field patterns in a hollow perfectly conducting pipe with elliptical cross section. The electrical field lines of the dominant TE mode as well as the magnetic field lines of the lowest TM mode are presented. The results are the same with literatures, and also give a correction to the field pattern of the lowest TM mode in elliptical waveguide.     

V波段圆波导TE_(01)模式激励器

V波段圆波导TE01模式激励器由矩形TE10模式到矩形TE20模式变换器和矩形TE20模式到圆波导TE01模式变换器组成。采用H面(磁面)转弯激励的方式实现矩形TE10模式到矩形TE20模式的变换;根据圆波导TE01模式的场分布特性,引入过模波导实现了矩形TE20到圆波导TE01的变换。计算结果表明设计的激励器转换效率在95%以上;模式纯度在98%以上的相对带宽可达4.2 GHz;其中在43.4 GHz处的最大转换效率为99.08%,纯度为99.20%。     

Simplified THz Instrumentation for High-Field DNP-NMR Spectroscopy

We present an alternate simplified concept to irradiate a nuclear magnetic resonance sample with terahertz (THz) radiation for dynamic nuclear polarization (DNP) experiments using the TE(01) circular waveguide mode for transmission of the THz power and the illumination of the DNP sample by either the TE(01) or TE(11) mode. Using finite element method and 3D electromagnetic simulations we demonstrate that the average value of the transverse magnetic field induced by the THz radiation and responsible for the DNP effect using the TE(11) or the TE(01) mode are comparable to that generated by the HE(11) mode and a corrugated waveguide. The choice of the TE(11)/TE(01) mode allows the use of a smooth-walled, oversized waveguide that is easier to fabricate and less expensive than a corrugated waveguide required for transmission of the HE(11) mode. Also, the choice of the TE(01) mode can lead to a simplification of gyrotron oscillators that operate in the TE(0n) mode, by employing an on-axis rippled-wall mode converter to convert the TE(0n) mode into the TE(01) mode either inside or outside of the gyrotron tube. These novel concepts will lead to a significant simplification of the gyrotron, the transmission line and the THz coupler, which are the three main components of a DNP system.     

任意分配比的微波功率分配器

圆波导中TE11模式波的电场在波导壁上随角度按正弦(或余弦)变化.如果在其侧壁上沿径向接两根互相垂直的波导,波导绕轴转动时两根波导中所分配的功率将随旋转角度而变化.这样就可以设计出任意分配比的微波功率分配器.通过HFSS的模拟计算完成了该功分器的设计,同时设计了一个新型的圆波导TE11模式转换器.     

Field Patterns in Double Circular-Groove Guide by Finite Element Method

The electromagnetic power coupling in symmetrical and asymmetrical double circular-groove guides have been analyzed by finite element method (FEM) in this paper. The electrical field patterns of the dominant mode and the first higher-order TE mode have been presented. The electromagnetic field of the dominant mode distributes with a concentration in the two grooves and the region between grooves as well for symmetrical double circular-groove guide, while it distributes with a concentration in the groove with larger radius for the asymmetrical double circular-groove guide. The electrical field patterns of the first higher-order TE mode in symmetrical and asymmetrical double circular-groove guide are also presented. The figures in this paper have important values in design of circular-groove guide power coupler for millimeter wave applications.     

9.4 GHz过模光滑壁TE11HE11模式变换器设计

采用半径微扰的光滑壁圆波导产生HE11模,避免了常规微波领域中采用的波纹渐变转换器在高功率微波领域应用时易发生齿间打火的不足。采用基于模式耦合理论的迭代综合方法优化了不规则的半径渐变轮廓,使输出产生组成HE11模的混合模式。并通过全电磁波仿真软件进行了对比, 输出波束标量高斯含量在9.1~9.7 GHz范围内均高于99.5%,功率容量4.9 GW。     

Guided modes in a rectangular waveguide filled with single-negative materials

Based on classical electromagnetic theory, characteristics of guided modes in a rectangular waveguide filled with a pair of single-negative layers are studied. The results show that only surface waves of TE mode can propagate in this peculiar waveguide, no TM mode in any forms can propagate in it. In addition, TE waveguide modes will be affected by permeability ratio μ₁/μ₂ and dielectric layer thickness ratio P. Finally, from the electric field distribution of TE mode, we find the amplitude and location of the electric field can be adjusted by changing the thickness ratio P.     

用于磁控管轴向辐射TE_(11)模式的紧凑型输出结构北大核心CSCD

提出了一种用于轴向输出相对论磁控管中具有TE_(11)辐射模式的紧凑型输出结构。该器件采用6谐振腔结构并工作在π模式上,通过合理设计谐振腔结构与输出圆波导之间过渡结构,模拟实现了圆TE_(11)模式微波的轴向输出。与传统衍射输出相对论磁控管相比,本文设计的轴向输出结构,不仅能在输出波导中获得更加纯净的微波模式,而且能减小磁控管的径向尺寸,使得系统更加紧凑化。初步的粒子模拟结果表明:当电压为280kV、磁场强度为0.5T时,该器件的工作频率为4.18GHz,输出功率为247.0 MW,功率转换效率达到21.9%。     

介质平面波导TE0模衍射场的光束参量

对于傍轴光束，提出了介质平面波导衍射场的近场模场半宽度、远场发散角半宽度和光束传输因子M^2等光束参量之间满足简单的关系式，三个光束参量均可直接由波导模式场分布精确计算，或由可实际精确测量的远场衍射频谱分布精确计算。M^2因子的计算公式可表述为以二阶矩和微分算子定义的近场模场半宽度的比值，或以二阶矩和微分算子定义的远场发散角半宽度的比值。最后推导出介质平面波导TE0模衍射场光束参量的解析函数和光束参量的范围。     

E面和H面方向图等化的双模圆锥喇叭设计

 介绍用于Φ7.3 m Cassegrain天线的高功率馈源喇叭的设计。为使E面和H面方向图在照射区域内具有高的等化度,选择双模圆锥喇叭作为馈源的结构形式。由于高功率源采用BJ-32波导输出信号,故馈源系统中还应包含一个矩形到圆形的模式转换器,将TE10模转换为TE11模。设计了双模圆锥喇叭和模式转换器,并进行了功率容量估算。测试结果表明,所设计的馈源达到了设计要求,理论计算结果和实验测试数据吻合良好。     

Field Patterns in Asymmetrical Double Groove Guide by Finite Element Method

The electromagnetic power coupling in asymmetrical double-groove guide is analyzed by finite element method (FEM) in this paper. The electrical field patterns of the dominant mode and the first higher-order TE mode have been presented. The electromagnetic field of the dominant mode is distributed with a concentration of energy in the wide groove region, while the electromagnetic field of the first higher-order TE mode is distributed with a concentration of energy in the narrow groove region. The results in this paper have important values in design of groove guide power coupler for millimeter wave applications.     

94 GHz回旋管过模波导模式转换与传输

 在耦合波理论的基础上,研究了94 GHz回旋管内置TE₀₃-TE₀₂-TE₀₁模式转换器和外接的TE₀₁-TE₁₁模式转换器。采用半径渐变微扰和轴线微扰几何结构以及不同的相位重匹配技术进行优化分析,得到了可靠的最优几何参量,设计出了紧凑、高效的94 GHz波纹波导模式转换器和蛇形线模式转换器。回旋管的热测实验中测出的模式样图表明,所设计的内置模式变换器有效地实现了TE₀₃-TE₀₂-TE₀₁的模式转换。     

同轴TEM-矩形TE10模式变换器的优化设计

用ＨＦＳＳ软件和网络理论对Ｓ波段同轴ＴＥＭ－矩形ＴＥ１０模式变换器进行了优化设计。同轴波导工作于过模状态,可同时传输ＴＥＭ、ＴＥ１１、ＴＥ２１模。模式变换器可应用于高功率微波的能量提取系统,优化设计方法可用于通过短路活塞来实现调配的同轴－矩表、圆波导－矩形的模式变换器。     

同轴TEM－余矩形TE10模式变换器的优化设计

 用HFSS软件和网络理论对S波段同轴TEM－矩形TE₁₀模式变换器进行了优化设计。其中同轴波导工作于过模状态,可同时传输TEM、TE₁₁、TE₂₁模。模式变换器可应用于高功率微波的能量提取系统,优化设计方法可用于通过短路活塞来实现调配的同轴－矩形、圆波导－矩形的模式变换器。     

高功率弯波导TE_(01)—TM_(11)模式变换临界角分析

在模式耦合理论的基础上 ,采用传统的波导轴线圆弧弯曲的方法 ,对TE0 1—TM11模式变换器的临界角进行了全面的优化分析。得出在临界角情况下 ,若考虑多模因素 ,则不能使TE0 1—TM11的能量发生全转换 ,而真正的最优化能量全转换角在临界角的附近 ,且转换的效率与弯波导曲率相关。     

Expanded-core channel waveguides: Single-mode analysis and application

A buried channel waveguide composed of several core layers (i.e., a expanded-core waveguide) is proved to exhibit single-mode wave characteristics and a mode field compatible with that of a standard single-mode fiber. A sufficient condition for achieving single-mode operation is derived using an effective-index method. The concept of expanded-core waveguides is then applied to the design of MMIC-based beam splitters. Numerical results show that the mode field would exhibit a strong evanescent wave for TM mode in case the core layers are not many enough, even the TE mode field is well confined in the expanded core region. This situation induces substantial polarization dependent loss and a large fiber coupling loss for TM wave. However, this situation can be improved by using more core layers for the expanded-core waveguide.     

径向线型模式变换器

 研究了一种通过改变波导内场分布的旋转对称性,可将高功率微波源输出的TEM模或TM01模转换为TE11模的径向线型模式变换器。介绍了该模式变换器的基本原理,即采用金属插板将同轴波导TEM模变换为4路90°扇形波导TE11模,各路扇形波导间所需的输出相位差通过将扇形波导转换为双层径向线传输来实现。基于这一原理,设计了一个中心频率为1.6 GHz的同轴TEM-TE11模式变换器,并进行了数值模拟计算,结果表明该模式变换器具有较高的功率容量,中心频率处反射系数为0.05,模式转换效率为99%,在1.52~1.68 GHz的频带范围内,模式转换效率大于90%。     

Ti扩散LiNbO_3光波导的喇曼散射

本文报道Ti扩散LiNbO_3光波导中四种直角配置的喇曼散射光谱。实验中,我们观测到了在这些配置下异常的喇曼光谱现象。这一现象可归结为光波导中入射光TE/TM模式的变换行为。     

Vectorial electromagnetic modes in V-shaped dielectric waveguides with application to quantum wire devices

The properties of V-shaped optical dielectric waveguides are investigated in detail using a vectorial finite element method. The fundamental modes exhibit extremely tight, heart shaped near field patterns. The maximum intensity of the fundamental mode is found to be vertically shifted with respect to the geometrical center of the waveguide. Fundamental and higher order mode properties are extensively studied, including mode patterns, dispersion curves and polarization properties. The local mode polarization of the two fundamental modes varies from a horizontal (vertical) orientation at the groove center to TM (or TE respectively) far in the side wings. The optimal design of waveguides for GaAs/AlGaAs quantum wire diode lasers and Quantum Confined Stark Effect modulators grown on V-grooved substrates is discussed.