Numerical Constructions of Testing Functions for Improving the Accuracy of MFIE and CFIE in Multi-Frequency Applications

We present a new approach based on numerical constructions of testing functions for improving the accuracy of the magnetic-field integral equation (MFIE) and the combined-field integral equation (CFIE) with low-order discretizations. Considering numerical solutions, testing functions are designed by enforcing the compatibility of the MFIE systems with the accurate coefficients obtained by solving the electric-field integral equation (EFIE). We demonstrate the accuracy improvements on scattering problems, where the testing functions are designed at a single frequency and used in frequency ranges to benefit from the design procedure. The proposed approach is easy to implement by using existing codes, while it improves the accuracy of MFIE and CFIE without deteriorating the efficiency of iterative solutions.