Numerical studies of forest backscatter in the VHF-band

The increasing interest for forest backscattering in the VHF band is stimulated by recent results from the CARABAS (20-90 MHz) SAR. Potential applications include forest biomass estimation and concealed target detection. For understanding the forest backscatter mechanisms it is important to develop scattering models and assess the limits of validity. Special consideration should be made to the fact that typical trunk and branch scattering is in the resonance region and that multiple scattering effects are important. A numerical method (FDTD) has been implemented which can be used to validate analytical scattering models. It features a five-layer PLM boundary condition, a far-field transformation method based on the reciprocity theorem, and an optional dielectric ground surface. It has been used to assess a coherent reflection model of a horizontal cylinder above dielectric ground. The results indicate an excellent agreement between the model and the FDTD method