Simulated analysis of the characteristics of SAR signal attenuation in forest areas

To fully understand the contribution of individual components of the forest to electromagnetic wave attenuation, in this work, the forest is simplified to a volume layer consisting of randomly distributed leaves and branches. We calculated the specific attenuation and skin depths of broadleaves, coniferous needles and branches using generalized Rayleigh-Gans (GRG) approximation and finite length lossy dielectric cylinder scattering models, as well as Foldy-Lax multiple scattering and optical theories. The results indicate that the specific attenuation of a single scatterer is related to the scatterer size and incident angle. For a forest volume layer, the attenuation contributions of leaves and branches were investigated, and the results show that the attenuation of leaves is more significant in the high-frequency domain. Subsequently, the skin depth changes with frequencies and scatterer density was analysed. At L-band (1.3 GHz), a monostatic SAR system will be unable to acquire underlying ground information if the height of the forest volume layer is greater than 31.1 m when the broadleaf number density is 25. At last, the variations in the attenuation of the polarization waves with the permittivity of scatterers and leaf shape were also discussed.