New fast and robust modelling algorithms for electrically large antennas and platforms

This paper presents two new modelling algorithms that was recently added to the commercially available GRASP software package for electrically large antenna and scattering problems. In particular, a new higher-order multilevel fast multipole solver (HO-MLFMM) provides very high simulation accuracy while requiring significantly less memory and CPU time than the commonly available low-order MLFMM. At the same time, the solver incorporates a generalised form of the underlying surface integral equations, which allows the use of non-connected meshes and enhances the robustness in real-life applications. As a further addition to GRASP, we outline a new Fast-PO algorithm which provide accelerated integration of Physical Optics currents as well as surface currents in general. The algorithm eliminates some of the limitations of previously published methods, e.g., by allowing observation points located well within the near-field region of the antenna without resorting to a much slower direct surface integration. The capabilities of the new algorithms are illustrated by examples involving a large reflector antenna ground station and a detailed model of a communication satellite.