Low-Frequency Time-Domain On-Surface Radiation Boundary Condition for Scattering Applications

An on-surface radiation boundary condition (OSRBC) procedure in the time domain is presented. The method extends well-known OSRBCs originally developed for high frequencies (short-time transients) to low frequencies or long-time transients in the time-domain. Starting with asymptotic approximations, we use an operator that is uniformly valid in time. Thus, the OSRBC developed here is valid at low and high frequencies. Its numerical implementation and its performance in low-frequency problems are demonstrated through examples of scattering from conducting cylinders. The advantage of the new OSRBC is that it is applicable to a wide range of frequencies, hence it can be applied to short- and long-time transients.