Improving the accuracy of the magnetic field integral equation with the linear-linear basis functions

Basis functions with linear variations are investigated in terms of the accuracy of the magnetic field integral equation (MFIE) and the combined-field integral equation (CFIE), on the basis of recent reports indicating the inaccuracy of the MFIE. Electromagnetic scattering problems involving conducting targets with arbitrary geometries, closed surfaces, and planar triangulations are considered. Specifically, two functions with linear variations along the triangulation edges in both tangential and normal directions (linear normal and linear tangential (LN-LT) type) are defined. They are compared to the previously employed divergence-conforming Rao-Wilton-Glisson (RWG) and curl-conforming $\hat{n}$ × RWG functions. Examples are presented to demonstrate the significant improvement in the accuracy of the MFIE and the CFIE gained by replacing the commonly used RWG functions with the LN-LT type functions.