New boundary integral equations for CAD of waveguide circuits:guided-mode extracted integral equations

Novel boundary integral equations which are applicable to the analysis of many kinds of waveguide circuits are presented. The new integral equations can treat the waveguide discontinuity problems like the scattering by the isolated finite-sized metallic objects or cavity problems and do not use normal-mode expansion techniques. They are suitable for the basic theory of CAD software for various waveguide circuits. The two-port and H-plane waveguide discontinuity problems which satisfy the single-mode and two-mode conditions are treated. The case of waveguide corner bend is considered as an example. Numerical examples are shown in order to confirm the validity of the new integral equations     

Investigation of electromagnetics problems for strip structures by means of the integral equation method

A method is proposed for the analysis of radiating and guiding strip structures. The method involves reducing the original electromagnetics problems to special integral equations that allow the development of efficient and universal simulation algorithms. Examples of the numerical analysis of the aforementioned practically important strip structures are presented.     

Direct singular integral equation methods in scattering andpropagation in strip- or slot-loaded structures

Problems of three-dimensional (3-D) scattering/hybrid-wave propagation for strip- or slot-loaded structures are often formulated in terms of systems of singular integral-integrodifferential equations (SIE-SIDE) of the first kind. Proper handling of the singular part of the kernels constitutes a major difficulty in carrying out method of moments (MoM). Three powerful techniques explored in the present paper provide efficient solutions by direct recourse to the theory of singular integral equations. In contrast to low-frequency methods wherein similar concepts are utilized for electrically narrow strips/slots, the proposed procedures are applicable uniformly to the whole range of widths from very narrow to very wide scatterers with remarkable accuracy. Numerical results are presented to validate and compare to one another the various numerical codes     

Analysis of directional grating-coupled radiation in waveguide structures

Radiation scattered from diffraction gratings on the surface of waveguides is analyzed using the volume current method. This technique allows the interpretation of the grating elements as scattering centers of the underlying waveguide mode, and radiating sources for the diffracted fields. The framework allows separation of the effects of the grating array global periodicity and the effects of the specific shape of the individual grating elements. A straightforward analogy between the effects of the grating element shape and the behavior of phased-antenna array systems allows a clear and intuitive understanding of the effects of blazed gratings on the directionality of grating-coupled radiation. The analysis is applied to some specific geometries.     

用光束传输法分析无间距方向耦合器和波导弯曲损耗

甲光束传输法(BPM)计算了无间距方向耦合器的传输特性、电极未对准对器件的影响和渐变折射率波导的弯曲损耗。     

Passive integrated-optical waveguide structures by Ge-diffusion insilicon

The realization of low loss optical channel waveguides and passive waveguide structures by a germanium indiffusion process into silicon will be discussed. Employing relatively simple technological processing like standard lithography, e-beam evaporation and diffusion, single-mode waveguides could be produced exhibiting polarization independent losses of as low as 0.3 dB/cm at wavelengths of λ=1.3 μm and λ=1.55 μm. S-bends fabricated with the same technology offered an excess loss of 1 dB at a radius of around 5 mm without any optimization. For a Y-junction designed with S-bends the maximum opening angle was determined to be 1.8° if an excess loss of 1 dB is allowed. The examination of directional couplers with various coupling lengths and distances revealed an excellent agreement between measurement and theory     

Analysis of planar structures by an integral approach using entiredomain trial functions

In this paper, a method based on an integral formulation with an excitation term is presented. The particularities of this approach lie in the utilization of entire domain trial functions and in the characterization of the coupling effect due to the excitation mechanism. The trial functions are taken as the TE-TM modes of a waveguide whose cross section corresponds to the shape of the discontinuity. The trial functions are computed and stored in the memory, then the study of complex planar structures becomes easy. A complete study is proposed, including the analysis of the coupling mechanism due to the source interaction and the characterization of higher order modes influence. This work is followed by two applications: a multiaxial discontinuity (bend discontinuity) in microstrip and in CPW. The computed results have been compared with data furnished by the literature. A good accuracy has been obtained     

Analysis of waveguide slot-based structures using wide-band equivalent-circuit model

Analysis of geometrically complicated waveguide-based slotted arrays and filters is performed using a simple equivalent-circuit model. First, the circuit parameters (inductance and capacitance) of a simple waveguide slot-coupler problem are obtained through moment-method (MoM) analysis. The values of the lumped LC elements are virtually constant over the frequency range of interest (the X-band) for specific waveguide and slot dimensions. Based on the equivalent-circuit model of a single slot of two coupled waveguides, more complicated structures are then analyzed, such as slot coupler arrays and slot-based waveguide filters. The scattering parameters of these structures are obtained through circuit analysis, and are verified using the MoM and finite-difference time-domain method. Excellent agreement is observed over a wide band of frequencies and is confirmed by experimental results.     

用波导模求解具有侧反射面的光学谐振腔

使用侧面抛光的激光棒的激光器能减小热光路畸变的影响,这是因为它构成一类特殊的谐振腔——带有侧反射面的腔。本文用波导模式的迭加求得了这种腔模式的解析表达式。     

Resonant grating waveguide structures

Under certain conditions, a resonance phenomenon can occur in waveguide grating structures. Such structures have multilayer configuration, the most basic of which is comprised of a substrate, a thin dielectric layer or semiconductor waveguide layer, and an additional transparent layer in which a grating is etched. When such a structure is illuminated with an incident light beam, part of the beam is directly transmitted and part is diffracted and subsequently trapped in the waveguide layer. Some of the trapped light is then rediffracted outwards, so that it interferes destructively with the transmitted part of the light beam. At a specific wavelength and angular orientation of the incident beam, the structure “resonates”; namely, complete interference occurs and no light is transmitted. This paper reviews previous investigations on the resonance phenomena and presents analytic and numerical models for evaluating the resonance as a function of the geometric and optical parameters of the structures and incident radiation     

On volume integral equations

The focus of this paper is on the volume integral representations to be used in constructing integral equations for composite volume media. The major thrust of the paper is to identify where derivatives of a discontinuous function arise in the derivation of the volume representation. Three different derivation methods are presented, resulting in identical representation independent of the derivation method. These representations agree with some in the existing literature and disagree with others. When an electric field formulation is considered, the source of disagreement manifests itself only when magnetic materials are present. Likewise, for the dual situation, the inconsistency appears for a magnetic field formulation of dielectric materials. This paper identifies the sources of error in the incorrect representations and its major contribution is the rigorously correct derivation of the representations to be used in volume integral equations. We also present numerical results for an integral equation derived from our representation. The numerical results employ only the E-field as the unknown and the singularity is handled in a manner analogous to a standard numerical treatment of the electric field integral equation.     

Electrodynamic analysis of resonance tags for radio-frequency identification of objects based on the method of singular integral equations

Electrodynamic analysis of resonance radio-frequency identification tags in the form of a system of plane concentric metal rings is presented. The analysis is based on the method of singular integral equations. The patterns of the structure and frequency dependences of the response of tags with various code combinations are obtained and studied. The results provided by the method of singular integral equations and finite-difference time-domain technique are compared. It is shown that the proposed method makes it possible to substantially optimize the analysis of the considered identification tags through minimization of the computation time.     

Active semiconductor-based grating waveguide structures

Under certain conditions, a high-finesse resonance phenomenon can occur in a grating waveguide structure (GWS). By varying these conditions, a shift in the resonance wavelength can be achieved. Specifically, utilizing the high finesse property of the GWS, small changes in the refractive index can result in a tuning range larger than the resonance bandwidth. Here, we consider different electric-field and charge carrier mechanisms that can affect the refractive index in semiconductor materials, and exploit them in order to control the refractive index change and, therefore, the resonance wavelength in the GWS. The predicted results are verified experimentally with an active GWS formed with semiconductor materials and operated in a reverse voltage configuration     

Bragg reflection waveguide composite structures

The Bragg reflection waveguide directional coupler is analyzed rigorously in terms of the normal modes of the complete structure. A perturbation analysis leading to an explicit expression for the coupling constant in a general configuration with nearly degenerate modes is performed. The results are compared to those for a conventional directional coupler structure. It is shown that the bandlike dispersion diagram arising from the periodic lateral confining media is responsible for the unique features of the coupling constant and coupling length that are observed     

Time domain adaptive integral method for surface integral equations

An efficient marching-on-in-time (MOT) scheme is presented for solving electric, magnetic, and combined field integral equations pertinent to the analysis of transient electromagnetic scattering from perfectly conducting surfaces residing in an unbounded homogenous medium. The proposed scheme is the extension of the frequency-domain adaptive integral/pre-corrected fast-Fourier transform (FFT) method to the time domain. Fields on the scatterer that are produced by space-time sources residing on its surface are computed: 1) by locally projecting, for each time step, all sources onto a uniform auxiliary grid that encases the scatterer; 2) by computing everywhere on this grid the transient fields produced by the resulting auxiliary sources via global, multilevel/blocked, space-time FFTs; 3) by locally interpolating these fields back onto the scatterer surface. As this procedure is inaccurate when source and observer points reside close to each other; and 4) near fields are computed classically, albeit (pre-)corrected, for errors introduced through the use of global FFTs. The proposed scheme has a computational complexity and memory requirement of O(N/sub t/N/sub s/log/sup 2/N/sub s/) and O(N/sub s//sup 3/2/) when applied to quasiplanar structures, and of O(N/sub t/N/sub s//sup 3/2/log/sup 2/N/sub s/) and O(N/sub s//sup 2/) when used to analyze scattering from general surfaces. Here, N/sub s/ and N/sub t/ denote the number of spatial and temporal degrees of freedom of the surface current density. These computational cost and memory requirements are contrasted to those of classical MOT solvers, which scale as O(N/sub t/N/sub s//sup 2/) and O(N/sub s//sup 2/), respectively. A parallel implementation of the scheme on a distributed-memory computer cluster that uses the message-passing interface is described. Simulation results demonstrate the accuracy, efficiency, and the parallel performance of the implementation.     

Experimental millimetric array using dielectric radiators fed by means of dielectric waveguide

A millimetric array is described which employs dielectric radiating elements excited by means of a dielectric waveguide. The design of the array is developed using the method of effective dielectric constants and a simple array theory. Measurements performed on a nonresonant prototype demonstrate its feasibility and its potential for frequency-scanning applications.     

Analysis of free processes in time varying circuit by means of generalized characteristic equations method

Developing methods of analysis of free processes in time varying circuit is important both for time varying and nonlinear radio circuits. The principle of linear connection brings together processes in time varying and nonlinear circuits. It is of special interest to extend the existing methods developed for radio circuits with stable parameters to time varying circuits. This article is devoted to one of such methods-the method of characteristic equations for differential equations with fixed factors.     

A potential integral equations method for electromagneticscattering by penetrable bodies

A method for computing the electromagnetic scattering by general inhomogeneous penetrable bodies is presented. The method is based on the volume equivalence principle and it uses the electromagnetic potentials as unknowns. The resulting coupled integral equations system is solved by the method of moments in combination with cubical and curvilinear meshes in the special case of purely dielectric scatterers. To show the accuracy of the method, numerical results of the transmitted and of the scattered fields are compared with existing analytical and experimental results