Fast simulation of microwave devices via a data-sparse and explicit CN-FETD method

For the fast design of microwave circuit, an unconditionally stable and fully explicit finite-element time-domain (FETD) method is presented. The Crank-Nicolson (CN) scheme is implemented leading to an unconditionally stable mixed FETD method. A hierarchical (H-) matrix algorithm is introduced to provide a data-sparse way to approximate the inverse of the sparse system matrix produced by the CN-FETD method which is dense originally. This approximate inverse can be computed and stored with almost linear complexity, and then the CN-FETD method can be computed explicitly at each time step. Examples of two microwave devices are simulated to demonstrate the efficiency and accuracy of the proposed method.