Transmission Line Matrix Model Research Articles

Reduction of edge reflections in the TLM model

The author points out that in the transmission-line-matrix (TLM) method, spurious reflection is encountered at the edge of the mesh. By transforming the infinite region exterior to a finite region and discretizing it by a second mesh, the magnitude of reflection is much reduced. Numerical results are presented together with an application. >

Evaluation of ultrasonic inspection and imaging systems for robotics using TLM modelling

SUMMARYAirborne ultrasound based sensor systems have been applied to a variety of problems in robotics and advanced manufacturing. These include slot and hole inspection, and systems suitable for workspace imaging and autonomous guided vehicle (AGV) navigation. The transmission line matrix (TLM) method of modelling wave propagation has been used in the evaluation of these systems. The model gives both graphical and numerical outputs, and allows an improved understanding of the interaction of ultrasonic waves and targets to be obtained.

Huygens and the computer-a powerful alliance in numerical electromagnetics

A time domain technique based on equivalent transmission line interconnections, referred to as the transmission line matrix model (TLM), is presented. The author retraces the history of TLM, from the original concepts of Huygens to the pioneering work of Peter B. Johns, and on to the latest developments in TLM modeling. The most important two-dimensional and three-dimensional TLM algorithms are explained, and new concepts in time-domain representation of frequency-dispersive boundaries are discussed. Some typical applications are described. >

Transmission line matrix modeling of disperse wide-band absorbing boundaries with time-domain diakoptics for S-parameter extraction

A numerical modeling procedure based on Johns time-domain diakoptics approach with space interpolation techniques for efficient transmission-line matrix (TLM) analysis of two-dimensional microwave circuits is discussed. Frequency-dispersive boundaries are represented in the time domain by their characteristic impulse response or numerical Green's function (Johns matrix). Almost perfect wide-band absorbing boundary conditions have been obtained with this technique, permitting accurate characterization of waveguide discontinuities and compounds. The application of these techniques saves considerable computer run time and memory when compared with conventional TLM analysis.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Moisture diffusivities for bran and endosperm during soaking of long‐grain brown rice

SummaryA three‐dimensional transmission line matrix (TLM) model, using axisymmetric elements, was developed for describing moisture diffusion during the soaking of long‐grain brown rice. On the basis of this model, moisture diffusivities for bran and endosperm were calculated as a function of temperature. Endosperm diffusivities of 0.92, 1.08 and 1.26X10‐10 m2 s‐1 and bran diffusivities of 0.11, 0.18 and 0.37x10‐10 m2 s‐1 were found, both at 30, 40 and 50°C respectively. The activation energies for moisture diffusion were calculated to be 13.08 and 49.85 kJ mol‐1 for endosperm and bran respectively.

TLM Modeling of Solder Joints in Semiconductor Devices

Transmission-line matrix (TLM) is an elegant technique for modeling heat flow in semiconductor devices. Unlike some other numerical methods a sense of the physical nature of the problem is retained and irregular boundaries, inhomogeneities, and temperature dependent thermal parameters can be easily incorporated. The inclusion of a layer of solder between a device and its PaCkage has a substantial influence on the temperature distribution. This theoretical paper investigates the effects of solder joint perfection and indicates the extent to which topographical methods such as infrared thermal imaging can give useful experimental results.

A two-dimensional transmission line matrix model for heat flow in power semiconductors

A nonlinear transmission line modelling (TLM) routine has been developed for the analysis of heat flow in axially symmetric power semiconductor devices. It has been used to simulate the thermal behaviour in the region of a hot spot.