A new boundary description in two-dimensional TLM models of microwave circuits

A boundary representation for the two-dimensional transmission line matrix (TLM) method of numerical analysis is described. In conventional TLM simulations, boundary conditions are realized by introducing the appropriate impulse reflection coefficients halfway between two nodes. Since the total field quantities are only defined on the nodes, their values at the boundary are not directly available from TLM solutions. The TLM procedure is modified so that boundaries can be placed across the nodes. The boundary conditions in TLM can then be formulated in terms of the field boundary conditions derived from Maxwell´s equations rather than in terms of impulse reflection coefficients. The essential differences between the conventional TLM and the proposed procedure are presented. Examples are given for several typical problems, and the results obtained with the two methods are compared. These are found to be in excellent agreement