Waveguide excited microstrip patch antenna-theory and experiment

An arbitrarily shaped microstrip patch antenna excited through an arbitrarily shaped aperture in the mouth of a rectangular waveguide is investigated theoretically and experimentally. The metallic patch resides on a dielectric substrate grounded by the waveguide flange and may be covered by a dielectric superstrate. The substrate (and superstrate, if present) consists of one or more planar, homogeneous layers, which may exhibit uniaxial anisotropy. The analysis is based on the space domain integral equation approach. More specifically, the Green's functions for the layered medium and the waveguide are used to formulate a coupled set of integral equations for the patch current and the aperture electric field. The layered medium Green's function is expressed in terms of Sommerfeld-type integrals and the waveguide Green's function in terms of Floquet series, which are both accelerated to reduce the computational effort. The coupled integral equations are solved by the method of moments using vector basis functions defined over triangular subdomains. The dominant mode reflection coefficient in the waveguide and the far-field radiation patterns are then found from the computed aperture field and patch current distributions. The radar cross section (RCS) of a plane-wave excited structure is obtained in a like manner. Sample numerical results are presented and are found to be in good agreement with measurements and with published data     

Rotman透镜多波束形成网络的数值分析

本文利用平板波导模型法与轮廓积分方程法结合分析了一种重要的多波束形成网络－Ｒｏｔｍａｎ透镜,首先建立了考虑色散效应的透镜的等效平板波导模型,然后选择适当的波导模式展开透镜端口上的场,并利用Ｇａｌｅｒｋｉｎ法求解其边缘上电场满足的轮廓积分方程即可得到透镜的多模式散射参数,再根据网络思想,将端口存在的高阶模作为加载,从而得到主模激励的散射参数,计算结果与实验结果吻合得很好。     

An approximate solution for coupling to a coaxial waveguide whichterminates at a conducting wedge

An integral equation is derived to approximate the aperture electric field for a coaxial waveguide that terminates at a conducting wedge. The integral equation is derived by retaining the standard kernel for the infinite-flange case and adapting the solution for the two-dimensional conducting wedge for use as the excitation term. The solution of this equation gives rise to an approximation to the TEM open-circuit voltage. Because only the excitation term is modified, the equation is useful for connectors that are greater than about one wavelength away from the corner. Theoretical and experimental results for the power transmitted down the coax are presented     

Multimode network representation of multiple inductive andcapacitive obstacles in parallel plate waveguides

In this paper the multimode network formulation is used to characterize a multiple obstacle or aperture discontinuity in parallel plate waveguide. The procedure leads to a frequency-independent integral equation. This equation is solved numerically by using the method of moments, allowing for the implementation of a very general and efficient code. The frequency-independent integral equation formulation and its numerical solution are first outlined. Then, we discuss the convergency properties of the procedure, and compare its results with other theoretical results available     

Domain integral equation analysis of integrated optical channel andridge waveguides in stratified media

A domain integral equation approach to computing both the propagation constants and the corresponding electromagnetic field distributions of guided waves in an integrated optical waveguide is discussed. The waveguide is embedded in a stratified medium. The refractive index of the waveguide may be graded, but the refractive indices of the layers of the stratified medium are assumed to be piecewise homogeneous. The waveguide is regarded as a perturbation of its embedding, so the electric field strength can be expressed in terms of domain integral representation. The kernel of this integral consists of a dyadic Green's function, which is constructed using an operator approach. By investigating the electric field strength within the waveguide, it is possible to derive an integral equation that represents an eigenvalue problem that is solved numerically by applying the method of moments. The application of the domain integral equation approach in combination with a numerically stable evaluation of the Green's kernel functions provides a new and valuable tool for the characterization of integrated optical waveguides embedded in stratified media. Numerical results for various channel and ridge waveguides are presented and are compared with those of other methods where possible     

Radiation of printed antennas with a coplanar waveguide feed

This paper presents an analysis of conductor-backed aperture antennas with multilayered substrate. These printed antennas are fed by a coplanar waveguide (CPW). The theoretical approach taken is to develop an integral equation over the aperture region and apply Galerkin's procedure in the spectral domain. The properties of printed antennas with a CPW feed are characterized. Numerical results include the scattering parameters, antenna pattern, and radiation efficiency. The reflection coefficient, input impedance, and far-field pattern are also compared with measurements and good agreement is observed     

Analysis of a cylindrical antenna containing an aperture coupledload

In this paper we present the basis for the analysis of shielded tuning networks coupled to wire antenna elements. The structure analyzed comprises three conducting cylindrical tubes that form an aperture-fed circular coaxial waveguide. Two methods are presented for formulating and solving integral equations for the structure. The first method is based on the mixed potential electric field integral equation enforced on the three cylindrical tubes, and the second is based on aperture theory. An end correction capacitance is used to adjust the reflection coefficient in the eigenmode expressions of the aperture method. The data obtained by the two methods are in close agreement. Differences in actual currents and equivalent currents obtained from solutions are discussed and reconciled     

Galerkin solution for the thin circular iris in aTE11-mode circular waveguide

An integral equation for the transverse electric (TE) field in the aperture of a concentric circular iris in a transverse plane of a circular waveguide is approximately solved using Galerkin's method. The aperture field is represented by a finite sum of normal TE and TM (transverse magnetic) circular waveguide modes that fit the circular aperture. The numerical convergence of the Galerkin solution is demonstrated using the resultant aperture field distributions and equivalent shunt susceptance for the case of dominant TE₁₁-mode excitation. The resultant aperture electric field distribution closely resembles that of the TE₁₁ aperture mode alone, except for edge contribution behavior at the edge of the iris. A resonant or capacitive iris is possible over a restricted range of frequencies     

Analysis of the power coupling from a waveguide hyperthermiaapplicator into a three-layered tissue model

The power deposition from a rectangular-aperture flanged waveguide into a three-layered stratified tissue medium is analyzed theoretically. The fields inside the tissue layers are expressed in terms of Fourier integrals satisfying the corresponding wave equations, while the fields inside the waveguide are expanded in terms of the guided and evanescent normal modes. An integral equation is derived on the aperture plane of the flanged waveguide by applying the continuity of the tangential electric and magnetic fields. This integral equation is solved by expressing the unknown electric field in terms of the waveguide mode fields and by applying a Galerkin procedure. The electromagnetic fields inside the tissue medium are then determined and patterns of the deposited power at frequencies of 432 MHz and 144 MHz for apertures of 5.6×2.8 cm² and 16.5×8.3 cm², respectively, are computed and presented     

The Reflection from an Open-Ended Rectangular Waveguide Terminated by a Layered Dielectric Medium

The measurement of reflection from an open-ended waveguide is a simple and nondestructive technique for determining the dielectric properties of materials. A flange-mounted waveguide is considered, the flange being pressed on an unknown material which may be of finite or infinite thickness. The relationship linking the reflection coefficient to the dielectric properties is obtained from a theoretical analysis of the electromagnetic field in the vicinity of the aperture. The theory includes the effects of both cross polarization and higher order modes. An integral equation is obtained, the kernel of which is the dyadic Green function in each medium. The method of characteristic modes is used for the numerical computation. The theoretical results are in good agreement with experimental measurements. Futhermore, a simple and handy technique for data inversion is provided.     

波束波导电磁传输问题的积分方程数值解

应用积分方程数值方法建立了任意形状波束波导中电磁传输问题的物理模型;在馈电端用模式匹配方法分析端口匹配状况,基于等效原理建立波导的场激励模型,应用边界积分方程匹配波导的理想电导体（PEC）边界条件,最后,通过矩量法（MoM）和多层快速多级子算法（MLFMA）等数值算法给出了波束波导电磁传输和口面辐射的场解。数值实例证明了上述分析方法对于电大尺寸波束波导电磁传输问题的有效性和精确性。     

The phase center position of a microstrip horn radiating in aninfinite parallel-plate waveguide

In this paper the field radiated by a flared microstrip line in an infinite parallel-plate waveguide with separation between plates of less than half a wavelength is studied. The field at any point of the parallel-plate waveguide is expressed as a summation of modal solutions of the Helmholtz equation. The phase center of the microstrip horn is calculated for uniform amplitude distributions along the horn aperture. The theory may be applied to obtain the phase and amplitude distributions along the output ports of microstrip bootlace lenses     

Line integral representation of the modal radiation for anopen-ended waveguide

A line integral representation of the Kirchhoff-type aperture integration is derived for an open-ended waveguide with arbitrary cross section, excited by an arbitrary mode. The problem is formulated by taking advantage of the equivalence between the radiation of the aperture and the radiation of the modal currents along the semi-infinite waveguide walls     

Scattering of modes by the end of a diaphragm-loaded planar dielectric waveguide

A planar dielectric waveguide loaded with an infinitely thin perfectly conducting diaphragm is considered. The problem of the guided mode reflection from the end of such a waveguide is analyzed with the help of the integral equation method and the variational method. Dependences of the fundamental mode reflection coefficient on the waveguide parameters and on the dimension of the aperture are calculated.     

Rigorous, multimode equivalent network representation of inductivediscontinuities

The theoretical derivation of the equivalent networks has been carried out by following the rigorous procedure used by M. Guglielmi and A.A. Oliner (1989) for the case of a metal strip grating at an air-dielectric interface. Following this procedure, network representations involving multimode coupling matrices are found in terms of the solution of a singular integral equation. The solution to this equation is shown to be known so that rigorous, multimode equivalent network representations for zero-thickness inductive windows and inductive obstacles in a rectangular waveguide can be derived. The network representations developed are valid for arbitrary aperture/obstacle dimensions and offset, and can accommodate a different medium on each side of the discontinuity. The analytic expressions obtained involve double integrations which are easily evaluated numerically. Numerical results are also presented indicating that the network representations developed are rapidly convergent so that they can be easily used to carry out computations involving an arbitrary number of propagating higher-order modes     

X波段矩形波导相控阵天线

本文给出X波段矩形波导相控阵天线的研制结果。将该天线作为电磁场边界值问题求解,建立了以孔径切向电场为未知函数的积分方程。经矩法处理后,在DJS-6型电子计算机上得到了数值解。制作了115元的无源小阵列。测量了阵单元方向图,加工了两个H面波导模拟器:HIC14和HIC29,进行了测试。宽角匹配介质板和孔径上匹配膜片的参数是通过理论计算和试验调整确定的。理论计算结果与测量结果相近。在86009600MHz频段和60扫描圆锥体内,天线的输入电压驻波比VSWR2。     

Low-Frequency Electromagnetic Penetration of Loaded Apertures

Low-frequency (quasi-static) electromagnetic penetration of an aperture can be reduced by loading the aperture with a conductive film or a bonded-junction wire mesh. A quantitative analysis of this phenomenon is carried out in this paper for a loaded circular aperture in a perfectly conducting ground plane of infinite transverse extent. Contact resistance between the aperture loading and the rim is taken into account. The quasi-static magnetic-field problem and the electrostatic field problem from which the aperture polarizabilities and penetrant fluxes are determined are shown to reduce to the problem of solving a single Fredholm integral equation. Exact (numerical) and approximate (variational) solutions to this integral equation are obtained, and the latter are used to represent the polarizabilities and penetrant fluxes by simple analytical formulas and equivalent circuits. These representations are found to be quite accurate when the contact resistance is not too large     

A Series Transformation for Diaphragm-Type Discontinuities in Waveguide (Short Papers)

In treating the problem of the inductive/capacitive diaphragm in waveguide with the integral equation or the moments method, it is often necessary to compute the matrix elements of the guide dyadic in terms of the aperture eigenmodes of the diaphragm. A transformation of the original series is presented that displays superior convergence properties of the numerical solution.     

A reactively loaded aperture antenna array

The use of variable reactive loads to control the beam direction of an antenna array consisting ofNclosely spaced waveguide-backed dielectric-filled rectangular slots is considered. Only the center waveguide is driven (no complex feed network is required for the array), and the other waveguides are short circuited at specified distances to provide reactive loading. The solution uses the method of moments applied to the integral equation for the equivalent magnetic current in the aperture region. The initial, design of the array is obtained by resonating the complex excitation voltages required for maximum gain with all of the elements driven. This is then improved by an optimum seeking univariate search method. Computed results are given for seven- and fifteen-element aperture arrays.     

Scattering at an offset circular hole in a rectangular waveguide

A solution is given for the problem of scattering at an offset circular to rectangular junction and at a thick diaphragm, with an offset circular aperture, in a rectangular waveguide. The method used is mode matching for computing one discontinuity. The difficulty arising from the fact that the eigenmodes of the two waveguides are known in different coordinate systems is overcome by simple transformation for the evaluation of overlap integral between the eigenmodes of each waveguide. Experimental results validate this method