A technique for the fullwave automatic synthesis of waveguidecomponents: application to fixed phase shifters

An efficient computer synthesis technique for waveguide components, based on rigorous field-theoretical models, has been developed. A computer code has been specifically set up for the automatic design of fixed phase shifters in rectangular waveguide technology. Only the electrical specifications are required to generate, normally in 15 to 20 min on a 386/16-MHz IBM PC, the geometrical structure of the components. The agreement with the experiments is shown to be so accurate as to avoid any tuning of the circuits realized. The efficiency and accuracy of the code is based on (i) a suitable segmentation technique of the microwave structure to obtain a very simple but rigorous network model; (ii) the efficient representation of the modal series for the electromagnetic fields; and (iii) a synthesis procedure based on a simplified model to obtain a good initial guess for the final full-wave optimization routine     

Computer Analysis of Gradually Tapered Waveguide with Arbitrary Cross Sections (Short Papers)

This short paper presents a general computer analysis of gradually tapered waveguide with arbitrarily shaped cross sectious. The technique combines coupled-mode theory with numerical methods for solving the uniform waveguide problem. The coupling coefficients are computed by using eigenvalues and eigenfunctions obtained numerically. The mode amplitudes are obtained either by numerical solution of a set of differential equations or from a closed-form solution. The applicability of this technique is illustrated by the analysis and measurement of two transitions. It is shown that theoretical prediction of coupled-mode amplitudes is reliable for gradual tapers where the flare angle is small. For large flare angles, more rigorous coupled-mode theory has to be employed.     

Phased-array radiator reflection coefficient extraction fromcomputer waveguide simulator data when grating lobes are present

Commercially available finite-element software that solves Maxwell's equations for arbitrary three-dimensional bounded structures has enabled phase-array radiator designers to perform waveguide simulator modeling of phased-array radiating elements on the computer very efficiently. Published work on waveguide simulator design has concentrated on array performance in the absence of grating lobes, a requirement for many radar applications. For such simulators, the reflection coefficient of each propagating mode at the waveguide simulator port gives the radiator reflection coefficient at a discrete scan angle. However, the design of limited scan arrays can lead to selection of an array element spacing that allows grating lobes in real space. When a waveguide simulator is modeled on the computer, and a grating lobe is present, the two waveguide modes representing the main lobe and the grating lobe will propagate in the waveguide simulator and they will be coupled together. The simulator port-reflection coefficient of either mode is not the true reflection coefficient seen by the radiating element. We describe a method for extracting the reflection coefficient of the radiating element from the waveguide simulator data when one or more grating lobes are present     

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     

基于LabVIEW的微波射频器件自动化测试系统设计

矢量网络分析仪是测试微波射频器件的专用仪器,在无线电测试领域应用非常广泛。为了提高测试效率,节省产品成本,构建自动化的测试系统成为必需。以通用的计算机为核心,使用LabVIEW虚拟仪器软件控制矢量网络分析仪,从而实现自动化的测试测量。构建虚拟仪器测试测量系统,关键在于软件的设计。本文主要介绍了微波射频器件自动化测试系统的结构组成、软件设计及软件的运行。通过现场测试波导器件表明软件运行良好,测试数据可靠,自动化程度高。     

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.     

Symmetrically Truncated Right-Angle Corners in Parallel-Plate and Rectangular Waveguides

The symmetrically truncated right angle E-plane corner is investigated as a function of the position of the truncation plane. The problem is treated by placing electric and magnetic walls in the plane of symmetry of the bend and solving the resulting boundary value problems assuming an incident TEM mode in parallel-plate waveguide. The results are directly applicable to the same type of corner in rectangular waveguide. In analyzing the problem an infinite set of first order differential equations arise which are appropriately truncated and solved on an electronic computer by means of a fourth order Runge-Kutta scheme.     

Slotted Line Measurements for Propagation Constant in Lossy Waveguide (Short Papers)

The propagation coefficient in a slotted waveguide partially loaded with a lossy dielectric can be determined accurately, in terms of the measured standing-wave pattern, by means of a computer program solving a set of transcendental equations. This determination is a necessary step in a permittivity measurement technique which was recently proposed by several authors.     

Test structures for characterization of electrooptic waveguidemodulators in lithium niobate

A method of determining the critical parameters of waveguide modulators, using a set of test devices fabricated on a single chip, is presented. The five parameters are the depth and lateral Ti diffusion lengths, the peak index change in the waveguides, the electrooptic coefficient, and the buffer layer dielectric constant. The finite element method is used for calculation of optical modes in waveguides with graded refractive index profiles. The integral equation method is used for calculation of the static electric field due to electrodes in a three-layer structure of air, buffer layer, and LiNbO₃. The test set includes a planar waveguide, Mach-Zehnder modulators, symmetrically perturbed directional couplers, and widened X modulators. Several test chips have been fabricated using different fabrication conditions. The parameter values determined using this method are compared with those reported by other authors     

Comparisons of Waveguide Losses Calibrated by the DC Potentiometer, AC Ratio Transformer, and Reflectometer Techniques (Correspondence)

Comparisons are made of the losses of two precision waveguide sections that were calibrated by three independent attenuation measurement methods. The loss measurement systems involved were the 1) dual-channel system which uses thermistors and a dc potentiometer test set, 2) dual-channel system which uses barretters and an ac ratio transformer test set, and 3) Nationaf Bureau of Standards reflectometer system which utilizes a quarter-wave short circuit and an IF attenuation standard. Loss values of about 0.05 dB, as calibrated by the three independent methods, typically agreed to within 0.0006 dB. It is believed that the results of these calibrations are representative of the best that can be achieved with current state-of-the-art techniques and available instrumentation for low-loss waveguide measurements.     

Calculation of Radiation from a Helically Cut Waveguide for a Gyrotron Mode Converter in the Quasi-Optical Approximation

We present results of calculations of the radiation from a helically cut waveguide launcher, a so-called Vlasov launcher, which is commonly used either internal or external to a gyrotron for purposes of mode conversion. A gyrotron internal mode converter consists of such a launcher that radiates the waveguide mode as a nearly Gaussian beam in free space followed by a set of mirrors to focus and direct the radiation. The radiation from the launcher is first calculated using a geometric optics representation of the waveguide mode. Then the radiation is calculated in the quasi-optical limit, including diffraction. These analytic results are compared to a rigorous calculation using the computer code SURF3D, which uses an electric field integral equation (EFIE) approach. Good agreement is obtained between the quasi-optical theory and the SURF3D calculation. The present results provide new insights into the accuracy of the quasi-optical theory and may be useful for the design and improvement of Vlasov-type mode converters.     

An application of fast integral wavelet transform to waveguide modeidentification

We introduce a very efficient method for computing the integral wavelet transform, with any compactly supported spline-wavelet as the analyzing wavelet, on a dense set of the time-scale domain. While the mathematical analysis of this algorithm will be presented elsewhere, the objective of this paper is to describe the computational scheme along with its computer implementation, and to demonstrate its effectiveness in the identification of mode propagation in a rectangular waveguide     

Functional Approximations for Solving Boundary Value Problems by Computer

The use of functional (as opposed to numerical) approximations in solving electromagnetic boundary value problems is presented. Galerkin's method is modified to simplify the choice of trial functions by permitting use of trial functions which do not satisfy certain boundary conditions. A test problem, the dielectric loaded rectangular waveguide, is worked using both the modified and unmodified Galerkin's method with identical results. This method is then applied to the arbitrary waveguide. The cutoff frequencies and computer drawn contour plots are presented for circular, rectangular, triangular and star-shaped waveguides.     

Optoelectronic Package Having Low-Loss Optical Waveguide Hole With Core–Clad Structure for Chip-to-Chip Interconnection

We have developed optoelectronic packages having optical waveguide holes with core–clad structures for chip-to-chip optical interconnection within computer systems. A rate of 10-Gb/s/ch chip-to-chip optical signal transmission has been demonstrated. The optoelectronic package we have developed consists of two guide pins and four-channel optical waveguide holes. The two guide pins are used to align an optical fiber connector with an optical device. The optical waveguide holes are used to transmit optical signals vertically through the optoelectronic package. Using the optical waveguide holes in the optoelectronic package, and high-quality signal transmission has been achieved.      

Glass-fibre waveguide with a triangular core

A new form of glass-fibre waveguide is described that has a triangular core. Estimates for the higher-mode cutoff of the guide are compared with values obtained by computer and by experiment.     

Scattering by a Cylindrical Post of Complex Permittivity in a Waveguide

An exact solution of the discontinuity problem of a circular cylindrical post of arbitrary complex permittivity centered in a rectangular waveguide with the axis parallel to the electric field vector of the dominant mode has been set up and numerical results based directly on this solution have been found rising an electronic computer. The method used divides the waveguide up into three different regions by introducing two imaginary plane walls perpendicular to the waveguide walls. In the center region, which contains the cylindrical rod, the electromagnetic field is expanded in cylindrical waves and in the outer regions the field is expanded in waveguide modes. By setting up the boundary conditions at all discontinuity surfaces and performing numerical matching of the fields at the two imaginary walls, a system of linear equatious determining the coefficients of reflection, transmission, and absorption of the field due to the cylindrical rod is found. The structure which is of most interest in the case of a plasma column is a coaxial structure consisting of an inner dielectric cylinder with complex permittivity (the plasma) surrounded by a dielectric sleeve with real, positive permittivity (the glass tube). The theory is therefore developed to apply generally for such structures. From the numerical results, curves have been obtained showing the relationship between the coefficients of reflection and transmission and the (complex) permittivity of the rod material. Such curves maybe used for deducing the microwave properties of a cylindrical rod from measurements of the reflection and transmission coefficient of the rod.     

任意多层介质波导本征值问题的网络分析

本文用微波网络的方法求解了任意多层介质波导的本征值问题;编制了一个分析N层介质波导色散特性和电磁场分布,并具有计算机图形功能的通用程序。通过对非对称多层介质波导场分布的实例分析,形象地说明了介质分支波导中模式转换和分裂的过程,并讨论了模式转换的一般规则。     

Application of the Boundary-Element Method to Waveguide Discontinuities (Short Paper)

A numerical method for the solution of scattering of the H-and E-plane waveguide junctions is described. The approach is a combination of the boundary-element method and the analytical method. A general computer programs has been developed using the quadratic elements (higher order boundary elements). To show the validity and usefulness of this formulation, computed results are given for a right-angle corner bend, a T-junction, an inductive strip-planar circuit mounted in a waveguide, a waveguide-type dielectric filter, and an inhomogeneous waveguide junction, and a linear taper. Comparison of the present results with the results of the finite-element method shows good agreement.     

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.