LASNE et al.: PHASE SIGNATURE FOR DETECTING WET SUBSURFACE STRUCTURES

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Fig. 14. (a)

distribution (oscillating curves) derived from the two-layer scattering model combined to FDTD simulations for

and

. Results are obtained for

and

cm. The smooth black curves in (a)­(d) represent the average value of

. (c) and

(b)

with respect to the rms height of the paleosoil roughness. (e) Maximum value of the copolarized phase with respect to the roughness

(d) Variation of

parameter  of the paleosoil for each permittivity value.

where

is the frequency variable and  the time variable.

, and the phase difference

is then obtained

tion

from

and

are the Fourier transforms of the hori-

zontally and vertically polarized backscattered electric field,

(25)

respectively

is the radar central frequency (1.6 GHz).

where

FFT

FFT

(24)

C. Results and Analysis

Fig. 13 shows the phase difference

The time shift

between the HH and VV signals corre-

obtained from nu-

(dashed curves) and

sponds to the time value at the maximum of the correlation func-

merical FDTD simulations for