A Novel FDTD Time-Stepping Scheme to Calculate RCS of Curved Conducting Objects Using Adaptively Adjusted Time Steps

The chief shortcoming of the conventional conformal finite-difference time-domain (CFDTD) method is a global time step reduction to ensure stability, due to the small irregular cells truncated by the curved conducting geometry. Introducing the local time stepping into the CFDTD method is an efficient way and has been numerically proven in our previous work. In this paper, we further employ the concept of the equivalent material constants into the integral form of Faraday's law to analyze the curved configuration with or without the coating. Hence, we can theoretically derive the stability criterion of each irregular cell based on the same procedure for the Courant-Friedrichs-Lewy (CFL) stability criterion. Therefore, the local time step size of each small irregular cell can be chosen adaptively. An adaptively adjusted time stepping procedure is presented and is theoretically proven to ensure numerical stability. The radar cross section (RCS) results of various curved conducting objects with the coating are computed. Comparisons of accuracy and efficiency of our method with other established methods are performed.