title: An unconditionally stable extended (USE) finite-element time-domain solution of active nonlinear microwave circuits using perfectly matched layers
abstract: This paper proposes an extension of the unconditionally stable finite-element time-domain (FETD) method for the global electromagnetic analysis of active microwave circuits. This formulation has two advantages. First, the time-step size is no longer governed by the spatial discretization of the mesh, but rather by the Nyquist sampling criterion. Second, the implementation of the truncation by the perfectly matched layers (PML) is straightforward. An anisotropic PML absorbing material is presented for the truncation of FETD lattices. Reflection less than -50 dB is obtained numerically over the entire propagation bandwidth in waveguide and microstrip line. A benchmark test on a microwave amplifier indicates that this extended FETD algorithm is not only superior to finite-difference time-domain-based algorithm in mesh flexibility and simulation accuracy, but also reduces computation time dramatically
keyphrases: active nonlinear microwave circuits perfectly matched layers global electromagnetic analysis time-step size Nyquist sampling criterion anisotropic PML absorbing material waveguide microstrip line microwave amplifier mesh flexibility simulation accuracy unconditionally stable FETD method finite-element time-domain method global EM analysis PML truncation FETD lattices truncation computation time reduction