矩形波导结中多介质柱散射特性边界元法分析

应用边界元法数值分析了n个端口矩形波导结中加载多介质柱的散射特性,对介质柱所在区域和除去介质柱后的空气区域分别用单连域和多连域问题的边界元法进行了分析。为了验证此方法的正确性,编制了一个通用的计算机程序,对几个算例进行了计算,结果与文献值一致。     

Multiple Dielectric Posts in a Rectangular Waveguide

This paper presents a complete analysis for a system of Iinear, homogeneous, and isotropic dielectric posts in a rectangular waveguide. These posts are assumed uniform along the narrow side of the waveguide, but are otherwise of arbitrary cross section and thickness. The scattering and impedance matrices describing the effect of the posts on the dominant waveguide mode are derived. The latter is then realized as a two-port T-network. A moment procedure is devised and applied to a set of test problems with a wide variety of post configurations to compute the scattering parameters and equivalent network elements. The accuracy and convergence aspects of the numerical solution are also investigated. The branch and network resonances are determined for some post configurations.     

Equivalent Source Method Approachto Compositely Postsina Rectangular Waveguide

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H-polarization diffraction by a thick metal-dielectricjoin

An analysis is presented of the H-polarization diffraction due to a material discontinuity formed by the junction of a thick dielectric half-plane with a metallic half-plane having the same thickness. This is accomplished by first considering the solution of several subproblems. These include the direct diffraction and coupling due to a plane wave incident on a loaded open-ended parallel plate waveguide and radiation and reflection by a waveguide mode. The final solution for diffraction by the metal-dielectric join is obtained by introducing a perfectly conducting stub within the loaded guide and subsequently using the generalized scattering matrix formulation with the stub brought to the waveguide opening. All the analysis relating to the subproblems is done by the dual integral equation approach. As expected, the final expressions involve several Wiener-Hopf split functions which are evaluated numerically or analytically     

矩形波导填充带有空气柱介质不连续性的边界元法分析

应用边界元法分析了矩形波导中填充带有空气柱介质不连续性的散射特性，编制了一个通用的计算机程序，对几个算例进行了计算。数值结果表明了该方法的有效性。     

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     

A multistrip moment method technique and its application to thepost problem in a circular waveguide

A moment method technique for solving obstacle problems in a waveguide is presented. Instead of using a multifilament current representation, which leads to a slowly converging series, a multistrip representation of the current is proposed. In the procedure, the matrix elements are determined by a series involving integrals of mode functions over the strips and the convergence is improved. The true currents on obstacle surfaces are replaced by equivalent planar currents in a number of waveguide cross sections inside the obstacle. The technique is applied to a pair of metallic posts in the TE₁₁-mode circular waveguide. Numerical results are compared with experimental data     

Analysis of waveguide inserted by a metallic sheet of arbitrary shape with the method of lines

In this paper, one type of waveguide three-dimension discontinuity, rectangular waveguide inserted by a metallic sheet of arbitray shape with zero thickness, is firstly analysed by using the Method of Lines. This waveguide discontinuity can be regarded as basic unit of microwave and MMW passive components and active circuits. Numerical results are in good agreement with physical meanings and other published data. Numerical results of several characteristics are presented at the end of the paper, including convergent characteristic of which the scattering parameters are depended on the number of discretization lines, dependence of scattering parameters on the size of metallic sheet and frequency response of scattering parameters.     

Numerical analysis of waveguide discontinuity problems using thenetwork model decomposition method

The use of the network model decomposition method for analyzing arbitrarily shaped H- and E-plane waveguide junctions is discussed. By using the polygon discretization technique previously introduced by the author (1990), the waveguide discontinuity region, which is surrounded by a metallic wall and the reference planes chosen, is first discretized; the topological model and the corresponding network model for the waveguide discontinuity are then established. In the formulation, equivalent current sources connected to the nodes on the boundary of the region are introduced to replace the effect of the field external to the region. The field internal to the region is approximated by the nodal voltage distribution of the network model, which can then be used to determine the scattering parameters of the waveguide junction. A diakoptic algorithm for the solution of the network model is also developed. Numerical results for various H- and E-plane junctions are given, and it is shown that the method compares favorably compares with other theories     

圆形槽波导到矩形波导结的有限元分析

设计基于圆形槽波导的元件经常会用到圆形槽波导到矩形波导结.应用有限元法(FEM)分析了N端口波导结.采用完全匹配层(PML)将槽波导的开放边界截断为有限区域,然后对圆形槽波导到矩形波导结的散射特性进行了数值计算,得出的散射参量为圆形槽波导振荡器输出结构的优化设计提供了依据.     

矩形波导E面不连续性的DDM/FEM分析

应用区域分解法(DDM)结合有限元法(FEM)分析矩形波导E面不连续性问题,将原求解区域分解为若干个非重叠的子域,在子域的虚拟边界上采用吸收虚拟边界条件,以保证相邻子域间的波传播。分别计算了矩形波导中加载双金属膜片和双介质柱时的散射系数,结果与有关文献一致。采用这种技术,大大地减少了对计算机内存的需求。     

Analysis of Substrate Integrated Waveguide Structures Based on the Parallel-Plate Waveguide Green's Function

This paper presents the full-wave characterization of substrate integrated waveguide structures. Substrate integrated circuits are considered as an ensemble of conducting posts placed in a parallel-plate waveguide and are analyzed in terms of the cavities formed by the top and bottom conducting plates and by the walls of the metallic vias. The field inside the parallel-plate waveguide is computed by considering the dyadic Green's function expressed as an expansion in terms of vectorial cylindrical eigenfunctions and considering the scattering from the ensemble of conducting posts. Coaxial or waveguide ports are included in the analysis as equivalent magnetic current distributions. Self-admittance and mutual admittance are calculated in a form that separates the parallel-plate contribution from the field scattered by the posts. Results relevant to structures already presented in literature will be shown and compared with simulations obtained with one of the most used articles of commercial software. It will be shown that an excellent agreement with published results is achieved together with significant improvements both in computational time and memory requirements.      

An Investigation of Nonreciprocal Periodic Structures

The properties of a nonreciprocal ferrite-loaded rectangular waveguide, which is periodically loaded by thin metallic "inductive" diaphragms, are investigated experimentally. The propagation constants of the structure are measured and are compared with predictions based on measured values of the scattering parameters of a single diaphragm in the nonreciprocal waveguide. The agreement between theory and experiment is generally good except for the smaller spacings between the loading diaphragms. This discrepancy is attributed to the effects of higher order mode interaction.     

Symmetrical N-port waveguide junction loaded with dielectric sleeveand metallic post

The present paper describes the development of a computer model that is able to predict the characteristics of the symmetrical N-port waveguide junction, which has a dielectric sleeve and metallic post inserted concentrically into its central cavity. Computational and experimental test results demonstrate that the resultant software package (which is compact enough to be run on an IBM 486 PC) can yield accuracies of ±0.5% for the scattering parameters of the junction     

Resonant Frequencies of Circular Substrate Integrated Resonators

In this letter, the characterization of circular resonators realized in substrate integrated waveguide technology is presented. Resonances are found by setting up the equations of the scattering for an ensemble of metallic posts in parallel plates waveguide and considering the nontrivial solution to the corresponding homogeneous problem. Resonant frequencies are then located by means of an efficient strategy, based on an estimate of the minimum singular value. In the last part of the letter a data fit formula of practical use is presented for circular resonators with a wide range of geometrical and electrical parameters resonating on TM₀₁₀ and TM₁₁₀ modes.     

Radiation characteristics of a waveguide excited dielectric sphere backed by a metallic hemisphere

The experimental results of the radiation characteristics of waveguide excited dielectric spheres backed by metallic hemispheres are reported. The test antenna consists of a dielectric loaded hemispherical horn excited by a circular waveguide. The test data have shown that such a structure produces a radiation pattern with low sidelobe levels, increased on-axis gain, and reduced 3 dB beamwidth as compared to a waveguide excited dielectric sphere of same diameter and an optimum horn having an aperture of identical cross section area. Also, it presents a low VSWR over the waveguide band.     

复杂波导元件的时域有限差分法分析

本文研究如何应用FDTD方法对一些复杂波导元件进行分析。应用子域连接技术,配合PML技术、连接边界法和非正交网格技术等,以波导双T、混合接头环耦合器等波导元件为例,得出这些器件的散射参数。对部分参数作出了测量,计算值和测量值吻合较好。算法的优点在于计算域小、计算时间缩短、共形性好及子域建模程序具有可移植性等。     

The resonance method for evaluating the impedances of theequivalent network for dielectric posts in a rectangular waveguide

The resonance method is applied to evaluate the impedances of the equivalent network for dielectric posts symmetrically located about a reference plane in a rectangular waveguide. Explicit relationships for the impedances of the equivalent lattice network of the posts in a rectangular waveguide are given in terms of the resonant frequencies of the rectangular cavity constructed by short-circuiting the waveguide at equal distances from the reference plane. A perturbational analysis is carried out to determine the resonant frequencies for a rectangular cavity loaded with slightly lossy circular posts whose largest cross-sectional dimensions are small compared with the wavelength. Sample numerical results for a single loss-free dielectric post illustrating the application of the derived expressions are given     

Absorbing boundary conditions for the finite-element analysis ofplanar devices

The finite-element method is used to determine the scattering matrices of open devices in two dimensions. Microwave and optical devices in which the fields are not confined to a finite region can be analyzed with the finite-element method if special boundary conditions are used to absorb outgoing radiation. The absorbing boundary conditions can be imposed by the addition of two terms to the usual functional for the scalar Helmholtz equation. Universal matrices are introduced to allow the additional terms to be easily assembled, for polynomial orders one through four. Results are given for the impedance of a parallel-plate waveguide radiating into free space and for the scattering parameters of three dielectric slab waveguide devices: a rectangular discontinuity, a feed structure, and a junction     

Narrow wall axial-slot-coupled T junction between rectangular andcircular waveguides

An analysis is presented of a T junction between rectangular and circular waveguides coupled through a long axial slot in the narrow wall of the rectangular waveguide. A moment method with entire orthogonal basis functions is used for deriving expressions for the elements of the scattering matrix. The effect of the wall thickness is taken into account by treating the coupling slot as a short section of a rectangular waveguide and matching the boundary conditions at the interfaces. The conditions satisfied by the scattering matrix of the junction are verified. A comparison between theoretical and experimental results on variation of coupling with frequency is presented