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     

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.     

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.     

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.     

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.     

A mode-matching technique for the study of circular and coaxialwaveguide discontinuities based on closed-form coupling integrals

A mode-matching scheme for the analysis of concentric circular and/or coaxial waveguide step discontinuities is proposed in this paper. An analytical evaluation of the involved coupling integrals for all possible discontinuities formed by any combination of a circular and a coaxial waveguide is performed. The originality mainly concerns the multimode excitation and scattering at a circular-to-coaxial waveguide step junction. Numerical results for a number of applications are compared against those of other techniques and/or measurements and are found to be in good agreement     

A Coaxial Wavewide Commutator Feed for a Scanning Circular Phased Array Antenna

A coaxial waveguide amplitude commutation feed system has been developed for application to the scanning circular array antenna problem. A dominant TEM mode and a pair of orthogonal TE/sub 11/ modes suitably excited at the input of a coaxial waveguide feed are employed to generate a simply commutatable low-sidelobe discrete amplitude distribution at the peripheral output ports of the coaxial circular array feed. The major advantages of the coaxial commutator feed compared to other circular array feed types are the broad bandwidth and small insertion loss simultaneously achieved with a simple feed geometry. The design and measured performance capability of a 30-percent RF bandwidth low-sidelobe coaxial commutator feed are described in detail.     

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.     

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。     

An Approximate Solution to Some Ferrite Filled Waveguide Problems with Longitudinal Magnetization

An approximate solution for the field structure and propagating modes in parallel plane, circular, and coaxial ferrite filled waveguide is presented. Bundles of plane waves are assumed to propagate in these structures which bounce back and forth along the guide. The solutions are classified into two types depending on the negative or positive equality of the incident and reflected waves. In the case of the circular guide the waves form a cone, and in the coaxial guide they form a frustum of a cone about the axis. The elemental plane waves are also assumed to satisfy Polder's relation and the boundary conditions at the guide walls. Simple relations are obtained with this equivalence for the propagation constant and the field. Comparison to rigorous theory is made in the case of the parallel plane and circular guide. Some experimental verification is presented for the completely filled coaxial waveguide.     

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     

Resonant Frequency of Open-Ended Cylindrical Cavity

The TE/sub 011/ mode of oscillation in an open-ended circular cylindrical microwave cavity is analyzed. The cavity consists of a circular waveguide that is terminated at each end with a thin cylindrical partition coaxial with the circular waveguide. The resonant frequency of the cavity is computed by using Laplace transform and Wiener-Hopf techniques. Numerical values for the resonant frequency are presented.     

A wideband orthogonal-mode junction using a junction of aquad-ridged coaxial waveguide and four ridged sectoral waveguides

A wideband orthogonal-mode junction (OMJ) using a quad-ridged circular coaxial waveguide and four single-ridged sectoral waveguides is described. The new structure is used for extracting a wide lower band signal from a coaxial dual-band feed. Theoretical results show that the broadband incoming signal in the quad-ridged coaxial waveguide can be coupled to four single-ridged sectoral waveguides with low reflection. The new structure transforms a complex system to a simple single-ridged sectoral waveguide where multi-band separation can be accomplished by a number of means. The transformation eliminates the interference among the excitation sources and enables the accurate mathematical modeling of the complete system possible     

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.     

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.     

Admittance of Irises in Coaxial and Circular Waveguides for TE/sub 11/-Mode Excitation

The admittance of irises in both coaxial and circular waveguides is deduced from a mode-matching technique. Design data for the effective admittance to TE/sub 11/ -mode excitation are given for a range of waveguide and iris dimensions.     

Cutoff Frequencies of Eccentric Waveguides

This paper discusses the uniform cylindrical waveguide formed by placing one conductor inside a conducting tube. Because of the complexity of the guide's cross section, the numerical technique of the point-matching method is adopted to solve the boundary-value problem. The formulations are carried out for the case when each of the conductors has an arbitrary cross section and also for the case when one of the conductors has a circular cross section. The coaxial waveguide modes, in which the field components have angular variations, split into odd and even modes when the center conductor begins to shift axis to form the uniform eccentric waveguide. However, only even modes in the eccentric guide correspond to the coaxial modes with no angular variations. The dependence of the cutoff frequency on the eccentricity of the guide is determined numerically for even and odd TE and TM modes. Experimental results verify the theoretical calculations for TE modes.     

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。     

Coaxial feeds for high aperture efficiency and low spillover of paraboloidal reflector antennas

Coaxial feeds produce an approximate sector-shaped pattern, an almost optimum pattern of a feed for high aperture efficiency and low spillover of paraboloid antennas. Such a coaxial feed consists of a central circular waveguide which is surrounded by one or more conductors with circular cross sections. Theoretical and experimental investigations on coaxial feeds excited by H11modes have shown that the first ring yields the highest increase in the aperture efficiency of paraboloid antennas illuminated by them. Measurements performed on paraboloid antennas illuminated by a coaxial feed with only one ring yielded aperture efficiencies of 68 to 75 percent for angular apertures of the paraboloidal reflector of100degto160deg. Circularly symmetric patterns in conjunction with almost linearly polarized aperture fields can be achieved by multimode coaxial feeds. The values for the aperture efficiency, which are calculated for paraboloid antennas illuminated by multimode coaxial feeds, nearly reach the theoretical optimum. The measured values are 68 to 80 percent. In addition, the multimode feeds produce very little cross polarization.     

Analysis of an End Launcher for a Circular Cylindrical Waveguide

The analysis of an end launcher type of transition exciting dominant TE/sub 11/ mode circular waveguide from a coaxial line is presented. The expressions for real and imaginary parts of impedance seen by the coaxial line are derived for the general case of offset launcher using self reaction of the assumed current over the loop. The dimensions of combined electric and magnetic loops having low input VSWR are determined. There is satisfactory agreement between theoretical and experimental results.