Quasi-Helmholtz Projectors for the Low-Frequency Stabilization of the Isogeometrically Discretized Electric Field Integral Equation

In order to low-frequency stabilize the isogeometrically discretized electric field integral equation (EFIE) based on B-splines, we derive quasi-Helmholtz projectors to form a preconditioner. To this end, we show how the projectors can be obtained efficiently for arbitrary polynomial orders of the basis functions. The approach is valid for single- and multi-patch descriptions of the geometry, which can be open or closed as well as simply or multiply connected without the need to search for global loops. Numerical results demonstrate the derived preconditioner's effectiveness in obtaining accurate scattered and radiated fields.