Transmission Line Matrix Method Method Research Articles

New compensation factors for the apparent propagation speed In transmission line matrix uniform grid meshes

Numerical models consisting of two-dimensional (2D) and three-dimensional (3D) uniform grid meshes for the Transmission Line Matrix Method (TLM), use sqrt(2) and sqrt(3), respectively, to compensate for the apparent sound speed. In this work, new compensation factors are determined from a priori simulations, performed without compensation, in 2D and 3D TLM one-section cylindrical waveguide acoustic models. The mistuned resonance peaks obtained from these simulations are substituted in the corresponding equations for the resonance frequencies in one-section cylindrical acoustical waveguides to find the mesh apparent sound speed and, thus, the necessary compensation. The TLM meshes are constructed over the voxels (Volumetric Picture Elements) of segmented MRI volumes, so that the extracted mesh fits the segmented object. The TLM method provides a direct simulation approach instead of solving a PDE by variational methods that must consider the plane wave assumption to run properly. Results confirm the improvement over the conventional compensation factors, particularly for frequencies above 4 kHz, providing a concrete reduction of the topology-dependent numerical dispersion for both 2D and 3D TLM lattices. Since this dispersion problem is common to all TLM applications using uniform grids, investigators in other areas of wave propagation can also benefit from these findings.

Método de Línea de Transmisión aplicado a la Acústica del Tracto Vocal a través de un Modelo 3D Reconstruido

The acoustic propagation in the human vocal tract using the Transmission Line Matrix method (TLM) has been simulated. Tri-dimensional meshes are built from segmented magnetic resonance images. Initially, simple models of one and two tubes were constructed to then simulate the same signal in a human vocal tract model whose shape represents the production of the open vowel /a/, simulating at the same time a human glottal signal. For the vocal tract model, the voice signals generated by the simulations were compared with voice samples from the same subject from whom the mesh was extracted. A compensation factor for the topology-dependent numerical dispersion for improving formant determination is proposed. It is concluded that the proposed compensation factor improves the effectiveness and accuracy of the TLM method.

Shape optimization of multi‐band antennas using the coupling between microgenetic algorithms and TLM method

AbstractThis paper presents a new combination between transmission line matrix method (TLM) and microgenetic algorithm (µGA). This coupling is used to design patch shapes of microstrip and planar inverted—F antennas (PIFA) for broad‐band or multi‐band applications. Measured results of the µGA/TLM optimized designs show good agreement with TLM simulation. Copyright © 2004 John Wiley & Sons, Ltd.

Integrating microgenetic algorithms with TLM method for dual-band planar inverted-F antenna design

The efficient coupling between microgenetic algorithms (/spl mu/GA) and the transmission line matrix method (TLM) to design two planar inverted-F antennas (PIFAs) for dual-band DCS/WLAN and GSM/UMTS standards, respectively, is presented. Measurement results of the /spl mu/GA/TLM optimised designs show good agreement with numerical simulation for a GSM/UMTS antenna.

A three-dimensional TLM simulation method for thermal effect in high power insulated gate bipolar transistors

The miniaturisation of electronic networks creates problems of heat dissipation. Good thermal management is therefore essential. Simulation of power electronic systems presents peculiar challenges due to the need of detailed modelling for both circuitry and control algorithms. Transmission Line Matrix method (TLM) is a powerful tool for analysing thermal effects in electronic circuits and high power devices. In this paper, thermal analysis for a 1200 A, 3.3 kV IGBT (Insulated Gate Bipolar Transistor) module has been announced at two levels, module and system level. For the module level analysis, the thermal of the IGBT module was investigated and analysed using the Three-Dimensional Transmission Line Matrix (3D-TLM) method. The results show a three-dimensional visualisation of self-heating phenomena in the device, including the effect of the use the Metal Matrix Composite (MMC) materials as base plate over conventional materials for electronic packaging thermal control and the use of the ceramics as substrate. This paper reviews the present status of the use of various thermal heat spreader such as Al SiC MMC, Cu–Mo and Graphite–Cu MMC and comparing those with copper-based heat spreader and the use of AlN, Diamond and Beo as substrates and their effect to dissipate the heat flux in heat sources localised in IGBT module design and taking into account effects of the geometry of the module, and specific material thickness because they play an important role in dissipating the generated heat and outweigh the thermal properties of the module. For the system level analysis, the total system that consists of the IGBT module and water-cooled heat sink is analysed suited to the modelling of many power electronics devices. The thermal simulations were run for various conditions and power levels including measurement and numerical results obtained by other simulators tools as MSC.PATRAN, FLOTHERM and LAASTHERM. Results are compared. The TLM method is found to be a versatile tool which is ideally suited to the modelling of many power electronic devices and proved very useful in the study of transient thermal effects in a variety of device structures.