A corner-free truncation strategy for FDTD method in target scattering

In this paper, the corner-free truncation (CFT) strategy is proposed to terminate the circular boundary out of finite-difference time-domain (FDTD) region. Using the principle of reflection-free optimal thin film, the permittivity ε and the permeability μ have been extended to the complex field. The electric conductivity σe and the equivalent magnetic loss σm relate to the complex value and are suitable for the impedance-matched condition (IMC). The propagation wave can be absorbed well at the circular boundary. Moreover, computational efficiency has been much enhanced when those useless square-corners have been eliminated by using the proposed method. In TMz wave, the sinusoidal wave is set near the circular boundary. Applying the CFT strategy, the Ez amplitudes and phases show the concentric circles in the different timesteps. Compared with the square PML, numerical experiments in near- and far-field have come to the fulfillment. At the same numerical example, the CFT strategy has higher accuracy than the conformal PML. These results have fully verified the effectiveness of the proposed algorithm.