Adaptive integral method for hybrid FE/BI modeling of 3D doubly periodic structures

The application of hybrid finite element/boundary integral methods to infinite periodic structures (antennas or frequency selective surfaces) is very attractive. For large unit cell apertures there is a CPU and memory bottleneck. To alleviate this we present an acceleration and memory reduction scheme for the boundary integral (BI) portion of the hybrid FE/BI method. The approach is based on the adaptive integral method (AIM) and is adapted here to periodic structures. For the given problem, AIM results in low O(n/sub s/) storage and O(n/sub s/ logns) CPU time requirements for the execution of the matrix vector products in the applied iterative solver (n/sub s/=number of surface unknowns). The paper focuses especially on AIM issues related to infinite periodic structures. Also, we present CPU time and storage comparisons with the more conventional implementation of the FE/BI method.