Quasi-Helmholtz projector including multibranch Rao-Wilton-Glisson basis functions for multiscale objects at low frequency

In this letter, a Quasi-Helmholtz Projector method including multibranch Rao-Wilton-Glisson (MB-RWG) basis function to calculate the scattering problem of multiscale targets at low frequencies is proposed. The loop basis function and the star basis function including MB-RWG basis function are constructed, and the loop basis function and the star basis function including MB-RWG basis function are used to construct the Quasi-Helmholtz Projector. The proposed method is coined MB-Quasi-Helmholtz Projector (MB-QHP) method. The MB-QHP method can effectively solve the low frequency breakdown (LFB) problem in electric field integral equation (EFIE). Compared with the MB-loop-star method, the condition number is lower, the convergence is faster, and the search for global loop is avoided. Meanwhile, due to the existence of the MB-RWG basis function, the proposed method can divide the calculation region into several regions with different mesh sizes. Numerical example shows the advantages of the proposed method.