A multipole analysis of a dielectric loaded coaxial rectangularwaveguide

A multipole analysis of a coaxial rectangular waveguide whose inner conductor is circular is made in order to determine the TE and TM modes of the system. The analysis is based on using multipole (dipole, quadrupole etc.) electric and magnetic current sources to generate field solutions in the waveguide. These solutions are used to match the electromagnetic boundary condition in a homogeneous coaxial rectangular waveguide and to determine the TE and TM eigenvalues of the waveguide system. Eigenvalue results are compared with results of the generalized spectral domain method and to eigenvalue results for a ridged waveguide. Propagation in a coaxial rectangular waveguide is also studied when the coaxial rectangular waveguide is loaded with lossy inhomogeneous dielectric material. A variational formula is used to relate the TEM, TE, and TM modes of an empty coaxial rectangular waveguide to the propagation in the loaded inhomogeneous dielectric waveguide     

6~20GHz同轴-矩形波导转换器的设计

宽带同轴-矩形波导转换器是高性能天馈系统的重要组件之一。针对现代电子系统对高频宽带特性的迫切需求,采用矩形波导宽壁平行加载金属双脊、同轴探针与脊波导非接触式转接、脊波导-矩形波导渐变转换的结构,设计了一种多过渡段、宽频带的同轴-矩形波导转换器,获得了6～20GHz工作带宽内插入损耗小于1dB、回波损耗小于-18dB的实测结果,可满足一般宽带天馈系统的馈电及测试要求。     

Photoconductive Terahertz antenna with radial symmetry

It has been demonstrated recently that it is possible to guide broadband Terahertz pulses utilising a novel coaxial waveguide. This technique is hindered by the difficulty in exciting the radially polarised fundamental mode of the waveguide. To optimise mode matching, a novel radially symmetric photoconductive Terahertz antenna is proposed. Using finite element method simulations and analytical calculations, it is shown that this antenna can generate the desired radial polarisation.     

任意块状介质填充矩形波导色散特性的数值分析

本文给出了一个用有限元法计算任意块状介质填充矩形波导的孪生波主模和高次模色散特性的标准程序。使用该程序,对十余种不同结构、不同介质加载矩形波导色散特性的计算,证实了所述程序的可靠性,文中对工字形介质填充波导的有用带宽作了详细的分析。本文所提供的各种色散特性曲线可供分析和设计有关微波元件时参考。     

Analysis of the Coaxial Ridge-Loaded Helical Groove Waveguide

The coaxial ridge-loaded helical groove waveguide is proposed in this paper. As an all-metal slow-wave circuit, it has advantages of good heat dissipation and great size, and thus is suitable for use of millimeter TWT. By means of field theory, the expressions of the dispersion equation and the coupling impedance of the coaxial ridge-loaded helical groove waveguide are obtained. The influence of various circuit dimensions on the dispersion relation and the coupling impedance is investigated by the results of numerical computation.     

An efficient high-order mixed-edge rectangular-element method forlossy anisotropic dielectric waveguides

A new efficient high-order mixed-edge rectangular element method is proposed for the analysis of lossy anisotropic dielectric waveguides. The space construction of the high-order mixed-edge rectangular element is investigated and the explicit form of the shape function is given. The high-order mixed-edge element yields higher accuracy and faster convergence than the lowest order mixed-edge rectangular elements without spurious solutions, and is more efficient compared to the high-order covariant projection element. The computations of the propagation constants in the rectangular waveguide and the slab loaded waveguide show that the accuracy of this high-order mixed-edge element is about one order higher than that of the lowest order one, and the nodes used in the calculation are only two-thirds as many as those used in the high-order covariant projection element having the same accuracy. The calculations of the dispersion curves for the dominant mode in the waveguide loaded with the lossy anisotropic dielectric block verify the accuracy and efficiency of the present method     

一种新的高次边缘元方法

讨论了一种新的高次边缘元方法，它不仅消除了伪解，并具有简单高效的特点．着重研究了二次边缘元的空间构造；给出了有关计算公式．对具有精确解的条形介质填充波导主模和高次模本征值的计算表明：二次边缘元方法的计算精度比一次边缘元提高约一个数量级．块状介质填充和衬底各向异性的微带线主模色散曲线的计算证实了该方法的精确性和广泛的适用性．     

Propagation in two circular coaxial waveguides

Two variants of the circular waveguide loaded with a coaxial dielectric rod are discussed. The first has conducting hoops around the rod, the second has conducting discs across the rod, the planes of the closely spaced hoops or discs being normal to the waveguide axis. The characteristic equations for the two systems are given, and a consistent mode notation is suggested.     

Some Results for Thin-Iris Loaded Periodic Waveguides

The planar waveguide holding planar obstacles is a prototype structure--its fields correspond to some sets of lowest modes in circular and coaxial line waveguides that use coaxial iris loading and in inductive iris loaded rectangular guides. An analysis of a periodically thin-iris loaded planar waveguide is offered, the procedure for which can also be applied to the other waveguides mentioned. A particular example for small iris separation is considered. Among the results of this study are adjustments to some formulas of Brillouin so as to allow consideration of large phase shifts per cell of periodic guide. The procedure, which can be recommended as a formula deriving technique, can find use with such other planar obstacles as the thick periodic iris, the interdigitally placed irises, or the single iris in a multimode guide. Some consideration is given to interdigital loading.     

Some Effects of Dielectric Loading on Ferrite Phase Shifters in Rectangular Waveguide

The use of dielectric loading with the ferrites in nonreciprocal transmission lines has becolme quite prevalent. The theoretical analysis of unloaded ferrite phase shifters in rectangular waveguide has been extended to the dielectrically loaded case by Soohoo. The boundary-value problem of ferrite phase shifters in dielectrically loaded coaxial lines, which possesses a transcendental equation similar to the waveguide case, has been throughly discussed by several authors. The present commumcation reports the solution of the boundary-value problem of a dielectrically loaded ferrite phase shifter in rectangular waveguide to yield values of the lossless propagation constant for various slab positions for both directions of propagation. The theoretical values of the differential phase shift for slab positions about the center of the waveguide were compared with the measured values for three different applied magnetic fields.     

基于行波法对螺旋波纹波导色散特性的仿真

为研究螺旋波纹波导的色散曲线特性,利用阻抗微扰法对螺旋波纹波导色散方程进行求解,并分析了波导尺寸的变化对色散特性的影响。针对目前采用谐振法仿真色散曲线时存在模式分割以及谐振点的选取问题,利用行波法(不属于波纹波导理论体系下的新方法)对不同频率下的色散值进行仿真求解。研究结果表明,基于行波法仿真得到的色散曲线与由Matlab计算得到的理论色散曲线吻合度好,计算过程不涉及波纹波导理论体系下谐振点的选取问题,相比传统的谐振法,整个仿真计算过程更简洁。     

Numerical analysis of dispersion characteristics of rectangular waveguides filled with arbitrary block-shaped dielectrics

The dispersion characteristics of rectangular waveguides filled with arbitrary block-shaped dielectrics are calculated by the method of finite element. A generalized program is given for the hybrid dominant and higher order modes. More than ten different rectangular waveguides loaded with various dielectric distributions have been investigated, and the results verify the reliability of the program. In particular, the useful bandwidth of the waveguide filled with I-shaped dielectric is analyzed in detail. The dispersion curves given in this paper are useful for analyzing and designing related microwave components of current interest.     

Propagation in Ferrite-Filled Coaxial Transmission Lines

The dispersion relations (/spl omega/-/spl beta/diagrams) for propagation of the quasi-TEM mode and higher-order symmetric modes in longitudinally magnetized ferrite-filled coaxial waveguide are presented. The dispersion relations for ferrite-filled coaxial cavity resonators are analyzed and presented graphically. The performance and operation of an X-band tunable ferrite filter is evaluated in light of the /spl omega/-/spl beta/diagrams     

The input impedance of a coaxial line fed probe in a cylindricalwaveguide

Dyadic Green's functions for determining the electric and magnetic fields in a cylindrical waveguide due to a radially directed infinitesimally short electric dipole are derived. The waveguide is shorted at one end and terminated at a perfectly matched load at the other. Both TE and TM modes are considered. Based on these dyadic Green's functions, the input impedance of a coaxial line fed probe in front of the plunger is derived. The formula is expressed in a closed form. Excellent agreement between theoretical results and experimental data for exciting the TE₁₁ mode in the X band for various probe positions is observed     

一种数值求解慢波结构色散曲线的新方法

运用场匹配法，推导出一种原则上可数值求解任意圆柱轴对称周期结构慢波波导冷腔TMon模色散曲线的方法。采用该方法编制了计算波纹波导和盘荷波导色散曲线的Matlab程序，计算结果与多维全电磁模拟软件结果的相对误差在1％之内。由于采用了数值积分算法，该方法的计算速度比传统的Bessel函数泰勒级数展开法更快。     

Evanescent and complex solutions in two circular coaxial waveguides

Evanescent and complex solutions for two variants of the circular waveguide loaded with a coaxial dielectric rod, that with conducting hoops around the rod and that with conducting discs across the rod are given. A previously given notation for the propagating solutions for the two systems is re-examined.     

Gain enhancement of dielectric resonator loaded waveguide antennas with dielectric overlays

The gain characteristics of a dielectric resonator loaded coaxial fed circular waveguide antenna (DRLWA) with overlaying parasitic discs have been investigated experimentally. Results indicate that, when properly spaced, the overlays can enhance the gain by more than 6 dB.<>     

Dispersion curves and modal fields of waveguide with FSS inserts

A rectangular waveguide with frequency selective surface (FSS) inserts has been studied. Dispersion curves are compared with measurements. The waveguide within a waveguide phenomenon is demonstrated. The effect of the array inserts on the dispersion curves and on the modal field distributions is discussed     

Analysis of an azimuthally periodic vane-loaded cylindrical waveguide for a gyro-travelling-wave tube

A cylindrical waveguide, provided with wedge-shaped metal vanes projecting radially inward from the wall of the guide, excited in the transverse electric (TE) mode, was analysed. The analysis was carried out considering the angular harmonics generated by the angular positioning of the vanes. A set of equations was generated in the Fourier amplitudes of field constants. The condition for nontrivial solutions for the field constants gave the dispersion relation of the structure. From the expression of power flow down the structure, its interaction impedance was also estimated. The shape of the dispersion characteristics and the value of the cutoff frequency as well as the interaction impedance characteristics of the waveguide were found to depend on the vane parameters their number as well as their radial and angular dimensions. The optimum vane parameters were obtained corresponding to the minimum variation of the slope of the ω-β dispersion plot, such parameters being useful from the standpoint of the bandwidth of a gyro-travelling-wave tube (gyro-TWT) using a vane-loaded cylindrical waveguide as the interaction structure. The dispersion and impedance characteristics, which were found typically for the TE₀₁ mode as defined for the structure, taking four vanes, were more sensitive to the number and angular width of the vanes than to their radial depth. The value of the interaction impedance, calculated at the potential beam position, was found to be higher for a loaded waveguide than for an unloaded one, and it depended on the frequency of operation relative to the cutoff. The interaction impedance also depended on the position of the beam relative to the waveguide wall where it was estimated, and hence the optimum beam position corresponding to the maximum interaction impedance was found. The theory was validated against the dispersion characteristics reported elsewhere typically for four-vane magnetron-like structures excited in the 2π mode. Although the present study was restricted to ‘cold’ analysis of the structure in the absence of the electron beam, it could provide important feedback for analysing a gyro-TWT, using a vane-loaded cylindrical waveguide, and hence for predicting the structure parameters for the wide-band performance of the device.     

Characterization and measurements of laterally shielded coplanarwaveguide at millimeter wavelengths

A laterally shielded coplanar waveguide consisting of a coplanar waveguide of finite width placed vertically in a cutoff parallel-plate waveguide is proposed for millimeter-wave applications. Advantages of the waveguide over the conventional coplanar waveguide are weak dispersion and low loss characteristics due to elimination of undesired surface waves and radiation. Simple but accurate analytical formulas for circuit design are derived and semi-empirical formulas for the weakly dispersive characteristics are also examined. Transitions to coaxial line are devised and the propagation constant is measured at millimeter wavelengths