Vegetation Effects for Remote Sensing of Soil Moisture Using NMM3D Full-wave Simulation

The transmission of microwave through vegetation layer has been studied by the Radiative Transfer Equations (RTE) and Distorted Born Approximation (DBA) model, both of which assume a uniformly random distribution of the scatterers in vegetation. In this paper, a hybrid method is developed for the Numerical Maxwell Model of 3D (NMM3D) full-wave simulation of vegetation field consisting of many plants. A geometry setup is used to include the plant structure and gaps. Using the Huygens's principle and vector cylindrical wave expansions, the T-matrix of single plant is extracted based on the near field solutions from Ansys High Frequency Structure Simulator (HFSS). The final scattered field is calculated using Foldy-Lax multiple scattering equations. The convergence of the T-matrix is tested and the hybrid method is verified with HFSS for the case of 4 wheat. The transmissivity of wheat at L-band calculated from the hybrid method is significantly higher than that of RTE/DBA.