Precise surface placement in transmission line matrix modelling

The Transmission Line Matrix modelling technique is a spatially discrete, time domain numerical modelling method. It has uses in many fields; however its main applications are for acoustic and electromagnetic modelling. This work focuses upon the study the positioning of surfaces which reflect and scatter waves within TLM models. In particular, the way in which the precise position of objects and surfaces are represented within the limitations of the model. Previously reported methods for improving surface positioning are investigated and evaluated. The previous methods are used as the basis for a new and improved method. The key features and performance of the method are appraised and areas for improvement defined. From this starting point, an enhanced method modifying the basic features and implementation is described. This enhanced method gives significantly improved results. Extensive testing of the original method and the enhanced method . are given in an unobstructed abstract case, clearly showing the performance differences of both methods and suitability for representing preCisely placed surfaces. Examples of the application of the method for both electromagnetic and acoustic modelling are given. Applications to ideal, abstract, and real world models are included. Results are compared with standard analytical benchmarks, results from other methods and measured data. The results show that there is a very clear and significant improvement in the performance of the TLM technique if the precise placement scheme given here is used.