Multi-frequencies Full-wave Simulations of Wave Propagation in Vegetation for Remote Sensing of Soil Moisture

A two-step hybrid method combining both the analytical and numerical solutions is used to perform full-wave simulations of a wheat field at three different frequencies. First, the full-wave simulations of one single plant is performed using the HFSS and the multiple scattering within a single wheat plant is characterized using the T-matrix of vector cylindrical waves. Second, the scatterings among different plants are considered using the Foldy-Lax equations of multiple scattering theory (MST) and the extracted T-matrix. The transmission of microwaves through wheat field at the L-, S- and C-bands are calculated using the hybrid method. Results show that the full-wave based transmission is much larger than those obtained from the radiative transfer equations (RTE) model. Moreover, the attenuation caused by the vegetation layer would saturate as frequency increases and the full-wave transmission has a weaker frequency dependence than those of the RTE.