Non-uniform Surface Impedance Absorbing Boundary Condition for FDTD Method

Recently, we reported a novel absorbing boundary condition (ABC), surface impedance absorbing boundary (SIABC). SIABC has a comparable absorbing performance compared to CPML, but requires a sufficient long distance between the boundary and the scatter. In this paper, we focus on this issue and introduce the non-uniform SIABC. Non-uniform SIABC archives a similar absorbing performance as the uniform SIABC at a same distance, while the number of the air buffer cells is much smaller. Therefore, it is possible for us to make it more efficient relative to uniform SIABC or CPML. An example of a patch antenna is discussed to explore the accuracy and efficiency of non-uniform SIABC. We also compare the memory usage for uniform SIABC, non-uniform SIABC, and 10-layers CPML. All the results indicate that non-uniform SIABC requires much less memory, needs much less time for simulations, which makes it a potential of being one of the most popular ABCs in FDTD method.