Modelling of absorptive boundaries in the TLM model

An important engineering problem is the prediction of the microwave scattering properties that depend on the physical shape of an object or device. A method that has been developed relatively recently is based on the transmission line matrix (TLM) model. In this method, space is divided into discrete cubic cells by a deformed rectangular mesh. Propagation of a wave from one side of a cell to the other is modelled as propagation of a wave along a link transmission line connecting the cube faces. In three-dimensions, there are three transmission lines per cell, forming a matrix with junctions or nodes in the centre of each cell. The numerical method used to solve the matrix reduces to copying pulse amplitudes from one node to adjacent nodes then multiplication by the scattering matrix at each node. This method produces as output a time series of field strength at each node