An improved model for a transient surface impedance boundary condition

An improved model for a transient version of the well known impedance boundary condition is presented using the analogy with an infinite lattice network. The input impedance for such a network is proportional to √s, where s is the Laplace variable, and thus corresponds to that required for the IBC. This is a marked improvement on models based on a ladder network, and more than halves the number of state variables required at each boundary node compared with that method. For maximum efficiency the network is truncated so that the bandwidth over which the required impedance is realized corresponds to that of the computed waveforms. The method is applied to a problem having an analytical solution