Hybrid method combining generalized T matrix of single objects and Foldy-Lax equations in NMM3D microwave scattering in vegetation

In this paper, we develop a hybrid method for Numerical Maxwell Model of 3D (NMM3D) full wave simulations of vegetation/trees. The hybrid method includes three steps: (1) calculating the generalized T matrix of every single object, (2) wave transformations and (3) solving Foldy-Lax multiple scattering equations (FL). We utilize the commercial software HFSS to extract the T matrix of a single object. HFSS enables us to perform full wave simulations of single objects with complicated structures. To validate the T matrix extraction method, a sphere is used since it has analytical solutions for the T matrix. For wave transformations, we develop the robust numerical method, which is verified by the analytical solutions of spherical wave transformations. In solving FL, the wave interactions of the singles objects are taken into account. The results of the hybrid method agree with those of the HFSS brute force method. In comparison, the hybrid method is much more efficient than HFSS for vegetation scattering and applicable to large problems such as full wave simulations of a tree.