Plane-wave diffraction by a wedge--A spectral domain approach

The canonical problem of plane wave diffraction by a wedge in the context of the spectral domain approach which exploits the relationship between the induced current on a scatterer and its far field is investigated. It is shown how the exact solution to the wedge diffraction problem can be manipulated in a form which enables one to interpret the far scattered field as the Fourier transform of the physical optics (PO) current on the two faces of the wedge augmented by the fringe current near the tip of the wedge. A uniform asymptotic expansion for the total field which slightly modifies the Ansatz in the uniform asymptotic theory of electromagnetic edge diffraction is constructed.     

Research on spectral domain immittance approach

In this paper, we have obtained the equations of electrodynamics for a gyrotropic medium using the Maxwell's equations. Through the Fourier Transforms (FT), the admittances of TM and TE modes in the electrically gyrotropic substrate and the magnetically gyrotropic substrate are given. Then we can use the spectral domain immittance approach to analyse the finline structures with a gyrotropic medium. The propating characteristics of the dominant mode in magnetized-ferrite-loaded double-layered finlines are studied, numerical results are presented which could be used in designing a finline displacement isolator.     

多层鳍线本征模的精确有效和完备求解

对多层鳍线现有的奇异积分方程法进行了如下改进：１）适当选择导体带所在平面切向电场和表面电流的线性组合,以使得导出奇异积分方程的级数具有很快的收敛特性;２）对于附加的边界条件,利用其级数的渐近特性来加速其收敛;３）给出系统计算任意阶特征矩阵元素的解析方法,以避免数值积分或对无穷级数求和;４）为完备地求解本征模的传播常数,构造了一个解析函数,保留特征矩阵行列式的所有零点,但消除其所有奇点．采用本文的奇异积分方程法,首次精确有效完备地求解了鳍线中的大量本征模．     

Modeling of discontinuities on lossy planar microwave structures by the spectral domain approach

New components appear, that require an improvement in the modeling methods in the microwave field. Indeed, in order to model the working of components such as the photoelectrical switch, whose substrate conductivity varies under the action of a judiciously chosen light beam, it has proved that taking losses in 3D problem was required. Thus, we have coupled the complex frequency concept to a dynamic modeling method: the spectral domain approach. This concept lays on the fact that the resonance frequency of a lossy resonator is complex. It enables to get the quality factor of the resonator and then its equivalent circuit, including the resistive elements that are characteristics of the losses. In the case of low losses, this general principle can be used through a perturbation method. We develop here this principle and use it for the study of a photoelectrical switch.     

Extended spectral domain approach for analysis of lossy cylindrical dielectric resonators

The spectral domain approach is extended for evaluating both the resonant frequency and Q factor of a lossy cylindrical dielectric resonator operating in TE/sub 0/ modes, taking into account the effects of conducting enclosure and supporting substrate. On the basis of the equivalence principle, the circular electric currents are introduced to simulate the fields inside and outside the cylindrical dielectric sample, which separates the original problems into two auxiliary structures with radially homogeneous multilayered dielectrics. Using the spectral immittance method in conjunction with the point-matching method, the characteristic equations are derived. The present technique has no need to determine the time-consuming, complex higher-order modes. Some typical examples are computed. The numerical results agree well with experimental data available in the literature.<>     

A SPECTRAL-DOMAIN IMMITTANCE APPROACH FOR THE CHARACTERISTICS OF FINLINES LOADED WITH ANISOTROPIC MEDIUM

The equations of electrodynamics for a gyrotropic medium by using Maxwell's equa-tions are deduced.Through Fourier transformation,the admittances of TM and TE modes inthe electrically gyrotropic substrate and magnetically gyrotropic substrate are given.Numericalresults of the dominant mode in magnetized ferrite-loaded double-layered finlines are presentedwhich could be used in designing finline ferrite devices.     

Numerically efficient spectral domain approach to the quasi-TEManalysis of supported coplanar waveguide structures

A numerically improved technique for the quasi-TEM analysis of supported coplanar waveguides is presented. The spectral domain method is combined with a special set of basis functions, to facilitate an accurate and efficient solution. The resulting integrals are evaluated using closed-form expressions instead of numerical integration scheme which leads to short CPU time. In this study, numerical results for the characteristic impedances of coplanar waveguides are presented. Comparisons are also made between the computed results and available ones. The charge density distributions on the center signal strip as well as on the ground plane are examined     

Analysis of multilayer printed arrays by a modular approach basedon the generalized scattering matrix

In this paper, a modular technique is used to treat infinite multilayer printed arrays with apertures and patches of irregular shapes. Each array layer is characterized by a generalized scattering matrix (GSM) from which the overall GSM of the multilayer structure is computed. The excitation of each element is modeled as a transition from the microstrip line to an aperture in the ground plane. The GSM of this transition is computed using the reciprocity theorem and spectral domain moment method. Several arrays have been analyzed by the proposed technique and the numerical results are in good agreement with other theoretical and experimental data     

Analysis of the superconducting coplanar waveguide by combining spectral domain method and phenomenological equivalence method

A conductor loss of the high T/sub c/ superconducting coplanar waveguide (CPW) is calculated by combining the spectral domain method (SDM) and the phenomenological equivalence method (PEM). An inductance of CPW is calculated by the SDM and the geometric factor is then calculated by using a numerical derivative of the inductance. This calculated geometric factor of the CPW is used in the PEM to calculate the conductor loss. Owing to the combination of the accurate analysis of CPW by SDM and PEM, the merits of two methods are obtained, which are: better accuracy, simple and fast calculation, and applicability to any case of penetration depth compared with the conductor thickness.<>     

Quasi-static solutions of multilayer elliptical, cylindrical coplanar striplines and multilayer coplanar striplines with finite dielectric dimensions - asymmetrical case

In this paper, fast, accurate, and simple analytic closed-form expressions are presented in order to calculate the quasi-TEM parameters of multilayer elliptical coplanar stripline (CPS), multilayer cylindrical CPS, and multilayer CPS, with finite dielectric dimensions by using conformal mapping techniques. The obtained computer-aided-design-oriented expressions are quite accurate and easy to apply in designing microwave integrated circuits and antenna applications. The results have also been compared with the ones of another conformal mapping method available in the literature and also confirmed analytically.     

Analysis of shielded striplines and finlines with finitemetallization thickness containing magnetized ferrites

The applicability of the spectral domain approach is extended to analyze various types of shielded planar transmission lines, taking the anisotropy of the magnetized ferrites and the finite metallization thickness into consideration. The numerical computations include the propagation characteristics of finlines and striplines and the metallization thickness effect in these lines. Numerical data of simpler structures are compared with the available exact solution as well as with published data     

Analysis of higher order modes on unilateral finlines with arbitrarily located slots

In this paper a rigorous method is presented which allows a complete calculation of all modes existing on a unilateral finline with an arbitrarily located slot. Also an investigation of the field distribution is possible. Hereby the behaviour of the different modes can be explained. This method also permits the determination of the propagation properties of higher order modes; thus information is needed for the calculation of finline discontinuities.     

应用谱域迭代算法计算理想导电腔体的RCS

本文介绍了利用谱域迭代方法计算理想导电腔体后向散射和RCS的方法,揭示了波谱在腔体内传播的过程.针对腔体截面形状的不同,给出了应用等效电磁流法解决腔体边缘绕射对口径场影响的方法.最后通过算例验证了方法的正确性.     

Analysis of the scattering and guidance of a two-dimensionally periodic metal grating structure by spectral domain method

The scattering and guidance of electromagnetic waves from a two-dimensionally (2D) periodic metal grating structure are investigated here. With the spectral domain analysis the dispersion characteristics for this structure are obtained. Properly taking into account the hybrid mode nature of the propagation problem the effects of mode coupling betweenTE andTM modes are examined. Numerical results will provide us valuable information for the design of new devices in 2D periodic structure, particularly in millimeter-wave frequency range, such as antennas, filters, couplers and distributed reflectors.     

An efficient approach to modeling of quasiplanar structures usingthe formulation of power conservation in spectral domain

An enhanced spectral domain approach (SDA) is developed for analysis of complex quasi-planar transmission lines. The method is based on a combination of the spectral domain formulation and power conservation theorem. The relationship between electric and magnetic fields is established inside dielectric layers by using the conventional SDA while the characteristic equation related to interface conditions is derived through the power conservation theorem. Maintaining the inherent advantages of the SDA, this technique is able to easily handle more complex quasi-planar structures. Generalized power formulation is also presented to calculate characteristic impedance. Convergence behavior is discussed considering the nature of power conservation. Various finlines with finite thickness of conductors are analyzed to demonstrate its applications     

A spectral domain approach for computing the radiation characteristics of a leaky-wave antenna for millimeter waves

A new method for evaluating the complex propagation constantbetain a leaky-wave structure comprising thin metallic rectangular strips etched on a dielectric rod of rectangular cross section is described. The radiation pattern of the leaky-wave antenna can be determined oncebetais known, since Re(beta) governs the direction of the main beam and Im(beta) accounts for the beamwidth and aperture efficiency. In addition the knowledge of the dependence ofbetaon frequency allows one to design the antenna for frequency-scanning applications. The method employed in this communication is based on the spectral domain approach that formulates the eigenvalue problem in the Fourier transform domain. Computed results are shown to be in very good agreement with experimental measurements.     

Analysis of multilayer planar circuits by a hybrid method

This letter proposes a hybrid method for the modeling of multilayer planar structures with locally inhomogeneous penetrable objects. By using the equivalence principle, the original problem can be decomposed into external and internal problems, which are formulated by the mixed-potential integral equation (MPIE) method and finite-difference time-domain (FDTD) method, respectively. Instead of directly implementing the continuity boundary conditions, an iterative approach is used to solve the hybrid FDTD-MPIE problem. Numerical results are presented to validate the hybrid method.     

Analysis of multilayer microstrip lines by a conformal mappingmethod

Multilayer microstrip transmission lines are investigated. The conformal mapping method is used to obtain simple analytical relations for the filling factors and the effective permittivity of two fundamental types of three-layer microstrips. Numerical results obtained by the present method are compared with available data from other authors