Multiple-directions asymptotic phase basis functions for efficient analysis of scattering from electrically large objects

A new set of multiple-directions asymptotic phase (MD-AP) basis functions based on curvilinear triangular patch is proposed for expansion of the current in integral equations solved by method of moments. Owing to the fact that the multiple phase disturbances brought from the object are considered in the construction of basis functions, the MD-AP basis functions figure out the bottleneck of the phase basis functions in the calculation of monostatic radar cross-section (RCS). The resultant system matrix is then solved using the inner-outer flexible generalised minimal residual algorithm accelerated by the multilevel fast multipole method. The parallelisation of the multilevel fast multipole method is also implemented for analysing electromagnetic scattering from electrical large objects. Numerical examples are given to demonstrate the accuracy and efficiency of the proposed method in monostatic RCS calculation.