Improvements to the numerical computation of the evanescent part in broadband MLFMA

Broadband multilevel fast multipole method can be used to accelerate numerical solution of large scale field problems with integral equations. By definition, broadband methods overcome the low-frequency breakdown from which the Rokhlin translator suffers, and so they work for all mesh densities, cube sizes and frequencies. One way to implement such an algorithm is to employ plane wave expansions with the Rokhlin translator on the super-wavelength levels, and multipole series in the sub-wavelength part.