Electromagnetic wave scattering from some vegetation samples

Abstract

For an incident plane wave, the field inside a thin scatterer (disk and needle) is estimated by the generalized Rayleigh-Gans (GRG) approximation. This leads to a scattering amplitude tensor equal to that obtained via the Rayleigh approximation (dipole term) with a modifying function. For a finite length cylinder the inner field is estimated by the corresponding field for the same cylinder of infinite length. The effects of different approaches in estimating the field inside the scatterer on the backscattering cross section are illustrated numerically for a circular disk, a needle, and a finite length cylinder as a function of the wave number and the incidence angle. Finally, the modeling predictions are compared with measurements.

Characterization of the Validity Region of the Extended T-Matrix Method for Scattering From Dielectric Cylinders With Finite Length

“…For the case of dielectric cylinder with finite length, an exact analytical solution is still elusive, and several approximation approaches have been proposed in the literature. One popular approach is the generalized Rayleigh-Gans (GRG) approximation [9,10], where the induced current in the cylinder is approximated by that of infinite length. This method is valid for a needle shaped scatterer with radius much smaller than the wavelength.…”

First Polarimetric GNSS-R Measurements from a Stratospheric Flight over Boreal Forests

“…The Physical Optics approximation for higher frequencies provides a fast algorithm when the radius of tree branches is large compared to the wavelength [33]. The GRG approximation for a needle was selected to evaluate the scattering on leaves because: (a) Needles are the best geometrical approximation for leaves in coniferous vegetation, and (b) GRG is valid for a scatterer with at least one of its dimensions small as compared to the signals wavelength [34]. Nonetheless, several simulations were performed to evaluate the differences with other methods: Rayleigh approximation for an ideal needle ( Figure A2a), Rayleigh approximation for a needle (Figure A2b), and the GRG approximation for a needle ( Figure A2c).…”

“…A much lower tree density for a biomass density of 100 t/ha (725 trees/ha instead ~2,700 trees/ha as in [32] for a tree height ~20 m) was required to make the simulations feasible. The electromagnetic models selected for the expression of the bistatic scattering matrices were the Semi-Exact solution for the branches S [33], the Generalized Rayleigh-Gans (GRG) approximation for a needle in the case of leaves S [34], and the Choudhury method for the soil S [35]. The Semi-Exact solution was selected because the radii of curvature of the branches of Northern Sweden forests is not an order of magnitude larger than the signals wavelength used in the simulations (λ = 19 cm).…”

“…The electromagnetic models selected for the expression of the bistatic scattering matrices S are the Semiexact solution for the branches [33], and the Generalized Rayleigh-Gans approximation for a needle in the case of leaves [34].…”

A New Propagation Channel Synthesizer for UAVs in the Presence of Tree Canopies

“…MST in [2] follows [4] and [5], which are mainly based on [10] and [11]. The corresponding theoretical background applicable to radiowave propagation was provided first in [12][13][14] and used also later in [15] or [16] for the case of a slab filled with branches and leaves.…”