A coherent scattering model to determine forest backscattering in the VHF-band

A coherent scattering model to determine the forest radar backscattering at VHF frequencies (20-90 MHz) has been de developed. The motivation for stud ying this frequency band is the recent development of the CARABAS Synthetic Aperture Radar (SAR). In order to model the scattering from branches and t runks, homogeneous dielectric cylinders placed above a semi-infinite dielec tric ground have been analyzed. An analytical approach, where the theoretic ally exact currents induced in an infinite cylinder are truncated, has been compared to a numerical solution using the finite difference time domain ( FDTD) method, If the first-order coherent ray tracing is included in the an alytical approach, the results match well with the numerically exact FDTD s olution. The results show that, in order to determine the VHF-backscatterin g from a forest stand, the coherent ground interaction is an important part and has to be considered. In this paper, modeling results are in good agre ement with CARABAS measurements.