document: An unconditionally stable extended -LRB- USE -RRB- finite-element time-domain solution of active nonlinear microwave circuits using perfectly matched layers This paper proposes an extension of the unconditionally stable finite-element time-domain -LRB- FETD -RRB- 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 -LRB- PML -RRB- 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
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