An asymptotic closed-form representation for the groundeddouble-layer surface Green's function

An efficient closed-form asymptotic representation for the grounded double-layer (substrate-superstrate) Green's function is presented. The formulation is valid for both source (a horizontal electric dipole) and observation points anywhere inside the superstate or at the interfaces. The asymptotic expressions are developed via a steepest descent evaluation of the original Sommerfeld-type integral representation of the Green's function, and the large parameter in this asymptotic development is proportional to the lateral separation between source and observation points. The asymptotic solution is shown to agree with the exact Green's function for lateral distances even as small as a few tenths of the free-space wavelengths, thus constituting a very efficient tool for analyzing printed circuits/antennas. Since the asymptotic approximation gives separate contributions pertaining to the different wave phenomena, it provides physical insight into the field behavior, as shown by examples     

Numerically efficient analysis of planar microstrip configurationsusing closed-form Green's functions

An efficient technique for the analysis of a general class of microstrip structures with a substrate and a superstrate is investigated in this paper using newly-derived closed-form spatial domain Green's functions employed in conjunction with the Method of Moments (MoM). The computed current distributions on the microstrip structure are used to determine the scattering parameters of microstrip discontinuities and the input impedances of microstrip patch antennas. It is shown that the use of the closed-form Green's functions in the context of the MoM provides a computational advantage in terms of the CPU time by almost two orders of magnitude over the conventional spectral domain approach employing the transformed version of the Green's functions     

A generalized method for the evaluation of mutual coupling in microstrip arrays

An analytical method for the evaluation of mutual coupling in microstrip arrays is discussed. The elements of the array are excited by microstriplines printed on or embedded in the substrate. As an example, the mutual coupling between microstrip dipoles electromagnetically coupled to embedded strip transmission lines is evaluated accurately. The presented method is valid in the millimeter range as weft as at microwave frequencies and does not have any substrate limitations. Also, it accounts for conductor thickness and surface wave excitation. Comparison with experimental results shows excellent agreement.     

Exterior moment method analysis of conducting scatterers by using the interior Green's function

A new method using a Green's function in the interior region of a conducting scatterer is proposed to obtain a mutual admittance matrix in an exterior moment method analysis. A numerical example of a two-dimensional magnetic strip source located on an exterior surface of a perfectly conducting rectangular cylinder shows the validity of the method.<>     

Minimising mutual coupling in thick substrate microstrip antennaarrays

A new method based on the reaction concept, is used to assess the mutual coupling experienced by two adjacent circular microstrip antennas on a thick substrate. The coupling owing to surface waves is separated out from that due to the direct radiation and the large interference effects exhibited by the former create deep nulls in the overall mutual coupling characteristic: the nulls being dependent on the given choice of substrate geometry and element separation distance. Finally, the application of this coupling minimisation technique to practical arrays having many elements is briefly commented on     

Exterior moment method analysis of conducting scatterers by usingthe interior Green's function and the method of least square

A method previously proposed by the authors in 1988 for obtaining the mutual admittance matrix in the moment method analysis by using the interior Green's function is improved by introducing the method of least square (MLS). A numerical example of a two-dimensional problem shows that accurate results can be obtained by introducing the MLS even when arbitrary sources are assumed for numerical experiments in the interior region     

The circular homogeneous-ferrite microwave circulator - an asymptotic Green's function and impedance analysis

A detailed analysis of the circular, homogeneous ferrite microwave circulator is provided. Particular emphasis is on the circulator's Green's function and the impact of the asymptotic term within the Green's function on convergence, data quality, and design methodology. The asymptotic term is shown to be logarithmic, which suggests that the Green's function is weakly singular when the source and observation points occupy the same location. With the Green's function properly understood, two techniques - one analytical and one numerical - are then offered to integrate that function in order to obtain Z-parameter data and, subsequently, S-parameter data. Data are provided to show rapid convergence of all parameters of interest. A small coupling angle approximation is then given for the Z-parameters and, from that approximation, a first-order design equation is obtained that relates the coupling angle to circulator radius. A circulator design example is presented and compared to a design associated with the Wu and Rosenbaum method; the comparison substantiates the small coupling angle approximation and design formula.     

凸表面上天线间互耦的射线分析法

本文给出了在电尺寸很大的理想导体光滑凸表面上,无限小磁矩或电矩在空间产生的电磁场的近似渐近解,利用该解可以准确有效地计算凸表面上天线间的互耦。此解中,表面塌沿Keller的表面射线路经传播,且在阴影边界过渡区域,包括对于源的邻城,它们仍然一致适用。除此之外,在给出的解中,通过一个系数T/K给出了关于表面场的表面射线绕曲的影响,其中,T表示表面射线的绕曲,K表示射线方向上的表面曲率。该解是由简单的典型问题的近似解导出的。给出了圆柱面和圆锥面上裂缝间互耦的数字结果,它与实验结果相吻合。     

Efficient analysis of input impedance and mutual coupling of microstrip antennas mounted on large coated cylinders

An efficient and accurate hybrid method, based on the combination of the method of moments (MoM) with a special Green's function in the space domain is presented to analyze antennas and array elements conformal to electrically large material coated circular cylinders. The efficiency and accuracy of the method depend strongly on the computation of the Green's function, which is the kernel of the integral equation that is solved via MoM for the unknown equivalent currents representing only the antenna elements. Three types of space-domain Green's function representations are used, each accurate and computationally efficient in a given region of space. Consequently, a computationally optimized analysis tool for conformal microstrip antennas is obtained. Input impedance of various microstrip antennas and mutual coupling between two identical antennas are calculated and compared with published results to assess the accuracy of this hybrid method.     

An integral equation approach to the analysis of finite microstripantennas: volume/surface formulation

An E-field integral equation for the analysis of finite printed circuit antennas with multiple dielectric regions is developed. In this analysis, the ground plane is considered to be finite. The dielectric substrates may be either lossless or lossy, and they may be inhomogeneous but must be finite. The equivalence principle is used to replace all conducting bodies by equivalent surface electric currents and all dielectrics by equivalent volume polarization currents. The respective boundary conditions on the dielectrics and the conductors are utilized to solve for the electric current on the entire structure. Typical results are presented to illustrate the potential of this method     

A direct discrete complex image method from the closed-form Green's functions in multilayered media

Sommerfeld integration is introduced to calculate the spatial-domain Green's functions (GF) for the method of moments in multilayered media. To avoid time-consuming numerical integration, the discrete complex image method (DCIM) was introduced by approximating the spectral-domain GF by a sum of exponentials. However, traditional DCIM is not accurate in the far- and/or near-field region. Quasi-static and surface-wave terms need to be extracted before the approximation and it is complicated to extract the surface-wave terms. In this paper, some features of the matrix pencil method (MPM) are clarified. A new direct DCIM without any quasi-static and surface-wave extraction is introduced. Instead of avoiding large variations of the spectral kernel, we introduce a novel path to include more variation before we apply the MPM. The spatial-domain GF obtained by the new DCIM is accurate both in the near- and far-field regions. The CPU time used to perform the new DCIM is less than 1 s for computing the fields with a horizontal source-field separation from 1.6/spl times/10/sup -4//spl lambda/ to 16/spl lambda/. The new DCIM can be even accurate up to 160/spl lambda/ provided the variation of the spectral kernel is large enough and we have accounted for a sufficient number of complex images.     

An overview of the hybrid MM/Green's function method inelectromagnetics

An overview is presented of a hybrid technique for solving electromagnetic radiation and scattering problems by combining the method of moments (MM) with a special Green's function. The method, referred to as an MM/Green's function solution, combines the ability of MM solutions to treat geometrically complex bodies with the accuracy and computational efficiency of Green's function solutions. Compared to a standard MM solution, the MM/Green's function solution reduces the number of unknowns and thus the computer storage requirements. In most cases the CPU time for the MM/Green's function solution is considerably less than that for a standard MM solution. An example problem of TM scattering by a semicircular strip in the presence of a circular cylinder is solved by the MM, and by the MM/Green's function technique with a matrix, exact eigenfunction, and high-frequency Green's function     

Computation of the equivalent capacitance of a via in amultilayered board using the closed-form Green's function

A method based on the quasi-static approximation for computing the equivalent capacitance of a via is presented in this paper. The geometry of a via consists of traces, pads and a perfectly conducting cylindrical rod; the via is buried in a multilayered dielectric medium with optional reference (ground) planes. The total number of traces, pads, and ground planes can be arbitrary, as well as the angles and cross sections. The method is based on the excess charge formulation of an integral equation applied in conjunction with the recently developed closed-form Green's function     

基于FDTD方法的微带线耦合噪声研究

基于时域有限差分（FDTD）方法,采用单轴各向异性介质完全匹配层为吸收边界条件,用上升沿为200ps、稳态值为1v的斜坡信号为激励源,在微带线间距保持不变,激励源及负载与微带线特性阻抗相匹配的情况下,研究微带宽度、PCB介质基板厚度和相对介电常数等参数对平直微带线近端耦合噪声和远端耦合噪声的影响,其次,研究微带线中部的直角弯曲对不同参数微带线耦合噪声特征的影响规律,和当微带线直角弯曲被45&#176;斜切后,前述不同参数微带线耦合噪声特征的变化,结果有助于微带线的优化设计。     

Efficient analysis of planar microstrip geometries using aclosed-form asymptotic representation of the grounded dielectric slabGreen's function

A newly developed closed-form asymptotic representation of the grounded dielectric slab Green's function is used in a moment-method formulation to calculate the propagation constant of an infinite microstrip transmission line and the input impedance of a finite-length, center-fed printed dipole. In these problems, source and field points are laterally rather than vertically separated with respect to the substrate. The conventional Sommerfeld integral and the plane wave spectral integral (PWS) representations of the microstrip Green's function converge very slowly in this case. However, the asymptotic closed-form representation of the Green's function does not have this limitation, and it remains accurate even for very small lateral separation between source and observation points. A modified form of the Sommerfeld integral representation is used only for observation points in the immediate vicinity of the source, while the asymptotic form is used elsewhere. Some numerical results based on this approach are presented and are shown to compare very well with previous results based on the corresponding exact-integral or PWS forms of the Green's function     

Improved analysis method for broadband rectangular microstrip antenna geometry using E-plane gap coupling

An analysis method for the broadband rectangular microstrip antenna geometry using E-plane gap coupling is considered. The return loss of the designed broadband antenna is computed theoretically and compared with experimental results for illustrating the usefulness of this method.<>     

An efficient computation scheme for the free space Green's function of a two-dimensional semiinfinite phased array

A simple scheme is developed to compute the Green's function of a periodic semiinfinite array in free space. It is based on the spectral representation of the fields radiated by an infinite linear array of dipoles. Results related to successive linear arrays are added in the space domain. This summation can be accelerated tremendously by using an elementary extrapolation technique. The resulting formulation converges everywhere in the plane containing the array, and the number of terms required to achieve a given precision increases slowly away from this plane.     

An efficient method to determine Green's functions of atwo-dimensional photonic crystal excited by a line source - thephased-array method

A novel and efficient method to determine Green's functions in photonic crystals (PCs), i.e., the phased-array method (PAM), is presented. The PAM is a combination of the plane-wave method and the array-scanning method, which is both more flexible and computationally faster than the eigenmodes expansion method. A complete derivation of the electric- and magnetic-field Green's functions associated, respectively, with an infinite electric and magnetic current line exciting a two-dimensional PC is given. Although the developments are presented only for a line source, the PAM can be extended to a dipole source. Thus, the PAM represents a promising method for the analysis of printed-circuit elements or antennas on PC materials. Numerical results for the Green's functions are shown for different positions of the source and a discussion about radiation patterns, asymptotic behaviors, and convergence characteristics is proposed     

Bias analysis of MUSIC in the presence of mutual coupling

The effect of mutual coupling in antenna elements heavily deteriorates the performance of existing array-based bearing-finding methods. Such a bias of MUSIC in uniform and general linear arrays is analytically studied and an explicit expression of a relationship between this bias and the effect of mutual coupling together with the direction of the incident source is given. The biases of different arrays are also compared to provide a reference when choosing the right array under the considerable effect of mutual coupling.