On Solving TM0n Modal Excitation in a Ka-Band Overmoded Circular Waveguide by the Conservation of Complex Power Technique

To measure the radiation properties of relativistic diffraction generator (RDG) in Ka-band, a TM0n modal excitation model is established, which consists of an overmoded circular waveguide and a coaxial line feeding probe. Using the transverse E-field mode matching and the conservation of complex power technique (CCPT), we deduce the scattering matrix at coaxial line to coaxial line and coaxial line to circular waveguide junctions. Then using the overall cascaded junction scattering matrix, the numerical results for the reflection coefficient of the coaxial line and the power distribution of TM0n multi-modal are presented. The numerical results are in agreement with HFSS simulation results and experimental results. The analysis shows that by choosing the appropriate position of coaxial line probe, the power proportion of the device operating mode excited in circular waveguide could be the largest.     

同轴线TEM波到圆波导TM0n模的转换

本文用复功率守恒技术对同轴探头在圆波导中激励ＴＭ０ｎ多模问题进行了严格的全波分析，得到了同轴线到圆皮导的总散射矩阵，并从散射矩阵出发求得了同轴线中的反射系数和在圆波导中激励出的各ＴＭ０ｎ传输模的功率分布。反射系数同实验结果作了比较，计算结果表明，当同轴探头在圆波导中激励出ＴＭ０ｎ多模时，圆波导允许传输的最高次模式功率含量大。     

Input impedance of a coaxial line probe feeding a circularwaveguide in the TM01 mode

By means of the conversion of complex power technique (CCPT), a formally exact full-wave solution is given for the case of a coaxial line probe fending a circular waveguide for TM₀₁ modal excitation. The overall scattering matrix of the coaxial-line-prove-circular-waveguide system is deduced. Numerical results for the impedance as `seen' by the coaxial line are presented and compared with experimental results obtained in the 9.0-11.5-GHz frequency range. Their agreement is reasonably good except at the lower frequencies (<10.0 GHz), where the TM₀₁ mode in the circular guide is close to its cutoff frequency (8.14 GHz)     

填充多层介质的共焦椭圆同轴线传播特性

采用在椭圆柱坐标系中分离变量的方法,得到了填充多层介质共焦椭圆同轴线模式特征方程.研究表明:当椭圆退化为圆时,利用角向和径向马修函数的渐进关系,可得到填充多层介质的圆形同轴线的模式特征方程,由此可见,圆形同轴线可看作椭圆形同轴线的特例;当椭圆同轴线内导体半长轴大小为零时,则椭圆同轴线就变成椭圆波导,同样的方法,可得到填充多层介质的椭圆波导模式特征方程.当填充一层介质时,得到了椭圆同轴线和椭圆波导的模式特征方程,结果和相关文献所得结果相同.作为示例,对填充一层介质和两层介质的椭圆同轴线中一些模式色散特性进行了数值计算,分析了椭圆同轴线中介质参数的变化以及椭圆同轴结构的变化等对其传播特性的影响.     

Scattering at Circular-to-Rectangular Waveguide Junctions

A formally exact solution is given for the problem of scattering at a circular-to-rectangular waveguide junction and at a thick diaphragm, with a centered circular aperture, in a rectangular waveguide. The method uses normal TE and TM mode expansions of the waveguide fields and traditional mode matching of the transverse electric and magnetic fields at the junction boundary. Exact closed-form expressions are obtained for the electric field mode-matching coefficients which couple the TE(TM) modes in the rectangular guide to the TE(TM) and TM(TE) modes in the circular guide. Numerical results are presented for the case of TE/sub 10/ mode propagation in the larger rectangular guide with all other modes cutoff. Convergent numerical results for the equivalent shunt susceptances of such junctions are obtained when about 12 modes (eight TE and four TM) are retained in the circular waveguide or in the circular aperture of the diaphragm. The results are graphically compared with formulas and curves due to the quasi-static theory of Bethe and the variational theory given in the Waveguide Handbook [2].     

Circular Electric Mode Directional Coupler

This paper describes a circular electric mode directional coupler, composed of two coaxial bifurcations in circular waveguide. The coupling coefficient of the directional coupler depends on the separation between the two bifurcations, and a hybrid junction for the circular electric mode may be obtained at the proper separation. The analysis is carried out in terms of scattering matrix elements characterizing each coaxial bifurcation. The scattering matrix elements were experimentally determined via the Weissfloch tangent method at 5000-Mc band. For convenience, experiments were carried out in sectoral waveguide instead of circular waveguide. Measured characteristics at 9000-Mc band are in good agreement with values determined by circuit calculations employing parameters of the coaxial bifurcation measured at 5000-Mc band. For the case of a hybrid junction, wide-band matching has been accomplished and verified experimentally. Applications of this directional coupler are outlined.     

Input Impedance of Coaxial Line to Circular Waveguide Feed

The expressions for the real, imaginary parts of the input impedance seen by a coaxial line driving a thin cylindrical probe in a dominant TE/sub 11/ mode circular waveguide are derived. The analysis is carried out by assuming that the cylindrical post is replaced by a curvilinear strip having maximum width equal to the diameter of the probe. Theoretical results on input VSWR and input impedance seen by a coaxial line are in close agreement with experimental data.     

Scattering and transmission matrix representations of multiguidejunctions

The scattering and transmission matrix representations of the mode-matching technique are generalized for multiguide junctions with arbitrarily shaped coupling apertures. A comparison between both representations is given with respect to the CPU time. The relative convergence phenomenon arising in cascaded discontinuities of multiguide junctions is investigated. A numerical criterion for choosing the correct mode ratio among the guides is presented. Also studied is the application to a kind of multiguide junction between a circular waveguide and a coaxial waveguide with hollow inner conductor     

A novel TEM-TE/sub 11/ mode converter

A novel mode converter that transforms coaxial transverse electromagnetic (TEM) mode to TE/sub 11/ circular waveguide mode is investigated. It is shown that with four metal plates inserted in the coaxial waveguide, the TEM mode will be converted to coaxial TE/sub 11/ mode, and finally, it forms a TE/sub 11/ conventional circular waveguide mode. The experimental test results are in good agreement with the computer simulations, which demonstrates the feasibility of the mode converter.     

Cutoff Variable Reactor (Correspondence)

When relatively high positive reactance is required for coaxial line circuits, the cutoff variable reactor can economize space. In Fig. 1, a schematic diagram of the cutoff variable reactor is shown. For z<0, there is the coaxial line; and for z>0, there is the cylindrical waveguide operated in cutoff region with the variable shorting plunger shorting the waveguide at the distance s. For simplicity, it is assumed that there is TEM mode alone on the coaxial line and TM/sub 01/ mode alone in the waveguide.     

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     

A rigorous analysis of a cross waveguide to large circularwaveguide junction and its application in waveguide filter design

A rigorous analysis is obtained for the problem of scattering at the junction of a cross-shaped waveguide and a larger circular waveguide. The general case of an arbitrary offset and orientation of the cross waveguide axes is considered. The fields matching over the cross aperture of the smaller guide is facilitated by using the transformation of the circular cylindrical Bessel-Fourier modal fields of the circular guide into a finite series of exponential plane wave functions. This permits an analytical finite series solution for the elements of the fields mode matching matrix, from which the general scattering matrix of the junction is obtained. The application of the formulation to circular waveguide filter design is emphasized in the numerical examples. Excellent agreements between theoretical and experimental results are obtained in all the numerical examples     

微波源中同轴提取区支撑杆的理论分析与设计

同轴提取区支撑杆的设计是MILO等同轴提取型高功率微波源设计的重要环节。本文根据场匹配原理导出了具有支撑杆的同轴提取区系统的传输方程和散射矩阵，并对同轴提取区各部分的微波模式进行了理论分析。对给定参数下的同轴提取区系统的散射矩阵参数进行数值计算，进而得到各微波模式系数，并对支撑杆进行了设计和参数优化。理论分析和数值计算都得出同样结论：对一定频率的微波来说，若同轴波导中第一个截止模式是Hn1则应选择n根支撑杆。这种支撑杆对TEM波的传播几乎无影响，可使微波源的束波互作用区及微波模式转换器和辐射器免受非旋转对称模式的影响。     

同轴探针激励圆波导输入阻抗的研究

用等效电路的方法推导了圆波导内径向探针的输入阻抗表达式以及等效电路各参数的表达式，实验测量表明单个同轴探针与圆波导匹配良好。理论计算与实验测量吻合较好。     

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     

同轴电探针耦合测高功率微波

本文从理论上对同轴电探针耦合检测高功率微波进行了简明的分析，推导了在国波导中传输TM（mn）和T（mn）模耦合度的计算公式。设计了一种同轴电探针，并用此探针近似测量虚阴极振荡高功率微波发生器产生的单次脉宽30ns的高功率微波，测得X波段脉冲峰值功率为1GW左右。此种测量高功率微波的方法虽不很精确，但作为一种监测的手段，具有结构简单，使用方便等特点。     

A new six-port microwave network; six-port magic junction

A six-port junction is proposed that consists of an H-plane symmetrical waveguide Y-junction with a coaxial line on one side of its axis and a circular waveguide on its other. The scattering matrix of the junction in an ideal case is derived using the symmetry properties of the structure. If both the coaxial and the circular waveguide arm are matched without destroying the symmetry, the arms of the junction are automatically matched and isolated as well, similar to the side arms of a conventional magic T. Therefore, the proposed device is called a six-port magic junction. These properties are confirmed experimentally in X-band. Some interesting applications based on the properties of the six-port junction are discussed     

高功率微波选模定向耦合器的设计制作

本文根据弱耦合函数理论，设计制作了圆波导ＴＭ０ｎ到３ｃｍ波段矩形波导ＴＥ１０模的选模定向耦合器用于高功率微波的测量系统，理论设计与实际测量结果与理论吻合较好 。     

The Susceptance of an Annular Metallic Strip in a Circular Waveguide with Incident TE/sub 01/ Mode

The principal aims of this paper are twofold: 1) to solve the problem of the scattering of a thin, perfectly conducting aonular strip suspended in a multimodal circular waveguide in which any number of TE/sub 0n/ modes can propagate, and with the aid of this result, 2) to give the susceptance of the thin annular strip in monomodal circular guide with an incident TE/sub 01/ mode. These are treated with a variational approach. Applying the appropriate Green's functions to the continuity equations for the transverse electric field yields a variational expansion for the scattering matrix elements. This is treated with a Rayleigh-Ritz procedure and matrix methods. Curves of normalized susceptance as a function of the free-space wavelength and the size of the annular metallic strip are shown. These results are in good agreement with experimental data. Tables of the scattering coefficients for a typical wavelength versus strip size are also included.     

On Solving Waveguide Junction Scattering Problems by the Conservation of Complex Power Technique

Normal mode expansions are used to mode match the tangential electric field at the transverse junction of two cylindrical waveguides. Instead of mode matching the tangential magnetic field the principle of conservation of complex power is invoked and leads, without a matrix inversion, to an expression for the junction's input admittance matrix, as seen from the smaller guide. Simple matrix algebra and the reciprocity theorem then provide the generalized scattering matrix of the two-port (with higher order modes included). It is also shown that the solution satisfies the continuity condition for tangential magnetic field in the junction's aperture. Numerical results are given for parallel plate waveguides with TEM, TE/sub 1/, and TM/sub 1/ incident fields, numerical convergence being achieved with about ten modes in the smaller waveguide.