Browsing by Subject "Absorbing boundary conditions"

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Open Access
Comparative evaluation of absorbing boundary conditions using Green's functions for layered media
(IEEE, 1995) Aksun, M. İrşadi; Dural, G.
Absorbing boundary conditions are comparatively studied using the Green's functions of the vector and scalar potentials for multilayer geometries and general sources. The absorbing boundaries are introduced as additional layers with predefined reflection coefficients into the calculation of the Green's functions. The Green's functions are calculated using different reflection coefficients corresponding to different absorbing boundaries and compared to those obtained with no absorbing boundary. This approach provides an absolute measure of the effectiveness of different absorbing boundaries.
Open Access
FDTD simulations of multiple GPR systems
(IEEE, 2003-06) Oǧuz, Uğur; Gürel, Levent
A multiple-GPR detection system was simulated. The main advantage of such a system was that it saves time by detecting both the transverse and the longitudinal positions of the target by a B-scan measurement, whereas the same detection can be achieved by a C-scan with a single-GPR system. Finite-domain time-difference (FDTD) method was employed to perform the simulations, in which the ground was homogeneous and the target was perfectly conducting.
Open Access
Frequency responses of ground-penetrating radars operating over highly lossy grounds
(IEEE, 2002) Oğuz, U.; Gürel, Levent
The finite-difference time-domain (FDTD) method is used to investigate the effects of highly lossy grounds and the frequency-band selection on ground-penetrating-radar (GPR) signals. The ground is modeled as a heterogeneous half space with arbitrary background permittivity and conductivity. The heterogeneities encompass both embedded scatterers and surface holes, which model the surface roughness. The decay of the waves in relation to the conductivity of the ground is demonstrated. The detectability of the buried targets is investigated with respect to the operating frequency of the GPR, the background conductivity of the ground, the density of the conducting inhomogeneities in the ground, and the surface roughness. The GPR is modeled as transmitting and receiving antennas isolated by conducting shields, whose inner walls are coated with absorbers simulated by perfectly matched layers (PML). The feed of the transmitter is modeled by a single-cell dipole with constant current density in its volume. The time variation of the current density is selected as a smooth pulse with arbitrary center frequency, which is referred to as the operating frequency of the GPR.