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Microwave, MTT-S International Symposium

作者： M. Righi J.L. Herring W.J.R. Hoefer NSERC MPR Teltech Research Chair in RF Engineering Department of Electrical & Computer Engineering University of Victoria Victoria BC Canada

A time domain model based on the Transmission Line Matrix (TLM) method for the rf drying of wood in a vacuum kiln is presented. The model is capable of addressing critical issues for the material processing industry such as drying time, penetration of the electromagnetic field into the material and evaluation of critical location where arcing may occur. The control and optimization of all of these variables leads to a highly efficient drying process yielding dry wood faster and with a higher quality compared to traditional convection drying. In addition the modeling of mass transfer and heat diffusion processes allows us to monitor temperature and moisture pressure in the wood sample so that critical values are not exceeded.

关键词： Electromagnetic coupling Transmission line matrix methods Radio frequency Kilns Electromagnetic modeling Materials processing Electromagnetic fields Electric variables control Heat transfer Diffusion processes

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Analysis of passive components for wireless applications using TLM electromagnetic simulations

Analysis of passive components for wireless applications usi...

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MTT-S Symposium on Technologies for Wireless Applications

作者： M. Righi C. Eswarappa W.J.R. Hoefer NSERC MPR Teltech Research Chair in RF Engineering Department of Electrical and Computer Engineering University of Victoria Victoria Canada

The electromagnetic simulation of passive components for PCS systems such as miniaturized ceramic bandpass filters is presented. We have used the transmission line modelling (TLM), a general-purpose space-time discrete method, to perform the simulations. We have compared the computed scattering parameters of the filter with available measurement results. The features of the filter responses agree well.

关键词： Electromagnetic analysis Analytical models Band pass filters Computational modeling Ceramics Time domain analysis Stripline Radio frequency Personal communication networks Circuit simulation

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Some thoughts on the relationship between finite elements, finite differences and TLM

Some thoughts on the relationship between finite elements, f...

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Antennas and Propagation Society International Symposium

作者： W.J.R. Hoefer NSERC/MPR Teltech Research Chair in RF Engineering Department of Electrical and Computer Engineering University of Victoria Victoria BC Canada

Peter Silvester (see Finite Elements for Electrical Engineers, Cambridge University Press, Cambridge, Third Edition, 1996) has pioneered the application of finite element methods in electromagnetics. While this has been a strong focus of his work, he always placed considerable emphasis on the greater picture in order to avoid the inherent limitations of specialization and to preserve a clear view of the larger context of field modeling. This paper demonstrates in simple terms that finite element, finite difference and transmission line matrix (TLM) models, approaches so very different at first glance, can lead to identical discrete algorithms for field computation under certain conditions.

关键词： Finite element methods Finite difference methods Lead Laplace equations Transmission line matrix methods Electromagnetic modeling Electrostatics Radio frequency Application software Context modeling

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Modal boundary conditions for waveguides of arbitrary cross-section with SCN TLM

Modal boundary conditions for waveguides of arbitrary cross-...

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Microwave, MTT-S International Symposium

作者： J.L. Herring M. Righi W.J.R. Hoefer NSERC/MPR Teltech Research Chair in RF Engineering Department of Electrical & Computer Engineering University of Victoria Victoria BC Canada

Modal absorbing boundary conditions are applied to a graded mesh using the hybrid node, and to homogeneous waveguides of arbitrary cross-section. The best performance is obtained with rectangular waveguides but examples show that the method can also be used for other geometries. A T-junction circular-to-sidecoupled rectangular waveguide example is given.

关键词： Boundary conditions Electromagnetic waveguides Rectangular waveguides Voltage Magnetic fields Radio frequency Geometry Transmission lines Symmetric matrices Transmission line matrix methods

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Transmission Line Matrix (TLM) Models of Electromagnetic Fields in Space and Time

Transmission Line Matrix (TLM) Models of Electromagnetic Fie...

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12th International Zurich Symposium and Technical Exhibition on Electromagnetic Compatibility

作者： Wolfgang J. R. Hoefer NSERC/MPR Teltech Research Chair in RF Engineering University of Victoria P.O. Box 3055 Victoria B.C. Canada V8W 3P6

ISBN: (纸本)9783952119914

This paper describes principles of, and progress in the modeling of electromagnetic structures in three-dimensional space and time with the Transmission Line Matrix (TLM) method. While this circuit-based technique has now reached a certain level of maturity, research efforts continue to improve its accuracy, speed, user friendliness, flexibility, and its compatibility with tools based on more conventional techniques.

关键词： Time-domain analysis Time-varying systems Computational modeling Transmission line matrix methods Scattering Accuracy Voltage Three-dimensional displays Power transmission lines Microstrip

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Absorbing boundary conditions for time-domain TLM and FDTD analysis of electromagnetic structures

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ELECTROMAGNETICS 1996年第5期16卷 489-519页

作者： Eswarappa, C Hoefer, WJR NSERC/MPR Teltech Research Chair AF Engineering Department of Electrical and Computer Engineering University of Victoria Victoria BC V8W 3P6 Canada

In this paper, the absorbing boundary conditions (ABCs) most commonly used in time-domain numerical methods such as the Transmission Line Matrix (TLM) method and the Finite Difference Time Domain (FDTD) method are reviewed. Such boundary conditions are required to simulate matched loads and open surfaces. We discuss and compare ABCs based on single impulse reflection coefficients, one-way equations, diakoptics or Johns matrices, and Berenger's perfectly matched layer (PML). Even though the emphasis is on applications in the TLM method, the major differences in the performances of these ABCs in TLM and FDTD are pointed out. Two ways of applying ABCs in TLM (voltage impulses and node voltages) are discussed. It has been observed that an ABC applied directly to the TLM voltage impulses absorbs better than the same ABC applied to the TLM total node voltages or FDTD field values. Furthermore, different ways of stabilizing one-way equation ABCs, such as adding damping factors, choosing proper discretizations for the boundary operators and employing digital filters, are discussed in detail. It has been found that in FDTD, the damping factors have a greater influence on the stability than the type of discretization of the absorbing boundary operators, while in TLM the opposite is true. Also, in a TLM simulation, the absorbing boundaries can be placed closer to a scatterer than in a FDTD simulation without affecting the accuracy. Several examples such as waveguides, microstrips, and high permittivity dielectric cubes have been considered to demonstrate the above observations.

关键词： Boundary conditions

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Accuracy of TLM solutions of Maxwell's equations

Accuracy of TLM solutions of Maxwell's equations

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Microwave, MTT-S International Symposium

作者： L. de Menezes W.J.R. Hoefer NSERC MPR Teltech Research Chair in RF Engineering Department of Electrical and Computer Engineering University of Victoria Victoria Canada

The physical origin of the coarseness and dispersion errors affecting TLM solutions of Maxwell's equations is investigated. The study is performed by solving the difference equations of the method analytically. The results confirm a reduction of the accuracy of the discrete solution near field singularities. This effect is a consequence of the finite number of spatial modes supported by the discretized domain.

关键词： Maxwell equations Difference equations Partial differential equations Closed-form solution Performance analysis Radio frequency Computer errors Propagation constant Dispersion Voltage

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Real time interface between 3D expanded-TLM and Yee's FDTD modules

Real time interface between 3D expanded-TLM and Yee's FDTD m...

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Antennas and Propagation Society International Symposium

作者： C. Eswarappa W.J.R. Hoefer NSERC/MPR Teltech Research Chair in RF Engineering Department of Electrical and Computer Engineering University of Victoria Victoria BC Canada

A real-time interface between 3D expanded node transmission line modelling (TLM) and Yee's (1966) finite-difference time-domain (FDTD) algorithms has been developed and validated. A structure can be subdivided in an arbitrary manner into connected TLM and FDTD subdomains which are updated simultaneously. In this way the specific advantages of both methods can be exploited when solving a given problem. The interface procedure has been validated by solving identical structures first with TLM, then FDTD, and finally with a combination of both. All three methods yield identical numerical results for equal excitation, space and time resolution.

关键词： Finite difference methods Time domain analysis Voltage Maxwell equations Scattering Transmission line theory Magnetic fields Radio frequency Transmission lines Electromagnetic analysis

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Improved excitation of 3D SCN TLM based on voltage sources

Improved excitation of 3D SCN TLM based on voltage sources

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Microwave, MTT-S International Symposium

作者： J.L. Herring W.J.R. Hoefer NSERC/MPR Teltech Research Chair in RF Engineering Department of Electrical & Computer Engineering University of Victoria Victoria BC Canada

The implementation of voltage, current, electric field and magnetic field sources is described. The correct voltage pulses that must be injected into a TLM network to produce a given temporal and spatial field distribution are obtained by placing voltage sources in a reference structure. This gives a field of known amplitude in which transients decay more rapidly than with the conventional approach. The method is applied to a waveguide.

关键词： Voltage Scattering Transmission line matrix methods Impedance Magnetic fields Equivalent circuits Admittance Microwave Theory and Techniques Society Waveguide components Matrices

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Fast S-parameter computation of a microstrip interdigital filter using TLM, Prony's and digital filtering techniques

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INTERNATIONAL JOURNAL OF NUMERICAL MODELLING-ELECTRONIC NETWORKS DEVICES AND FIELDS 1996年第3期9卷 237-248页

作者： Eswarappa, C Hoefer, WJR NSERC/MPR Teltech Research Chair in RF Engineering Department of Electrical and Computer Engineering University of Victoria Victoria B.C. Canada V8W 3P6

A spectral estimation technique based on Prony's method has been used to analyse a five section microstrip interdigital filter with the TLM method. The time response of the filter is expressed as the sum of only five damped sinusoids, yielding an analytical expression for the time response. Furthermore, since an analytical Fourier transform exists for this expression, the frequency response is obtained without applying the fast Fourier or discrete Fourier transform. This typically reduces the time required for a TLM analysis by a factor of five. The approximation agrees very well with a full TLM time response. It is also shown that the numerical noise due to single precision computation of the absorbing boundary algorithm can be eliminated by digital filtering techniques. The effect of the via holes used for grounding the quarter-wave resonators of the filter has been included by discretizing them along with the rest of the circuit. Scattering parameters for the filter compare well with measurements published by Swanson.

关键词： Digital filters

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