Goal-Oriented Error-Estimation for<tex>S</tex>-Parameter Computations

Accurate and efficient goal-oriented error estimates for adaptive finite-element computations of scattering parameters are presented. The estimates are derived using dual problems and computed using special hierarchical basis functions, tailored to agree with the Ne/spl acute/de/spl acute/lec interpolant. The method is tested on a two-dimensional waveguide cavity resonator with several reentrant corners. When uniform mesh refinement is used, the convergence rate is limited to h/sup 4/3/, independently of the element order due to singularities. However, with adaptive h-refinement guided by the presented error estimates, the convergence rate is increased to h/sup 2p/ for elements of (complete or incomplete) order p/spl les/3, even in the presence of singularities. Further, the accuracy of the scattering parameters can be increased significantly by adding the estimated errors to the computed results.