Browsing by Subject "Ground penetrating radar systems"

Now showing 1 - 6 of 6

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.
Open Access
On the frequency-band selection for ground-penetrating radars operating over lossy and heterogeneous grounds
(IEEE, 2001-07) Oǧuz, Uğur; Gürel, Levent
The frequency-band selection for ground penetrating radars operating over lossy and heterogenous grounds was discussed. The simulations were carried out using perfectly matched layer (PML) absorbing boundary conditions (ABC). The results demonstrated that for conductivities below 0.5 S/m the change in centre frequency does not influence the energy scattered from the deeper target. The selection of the center frequency thus influences the GPR measurements for the measurements performed over a highly-conducting soil.
Open Access
Simulation of TRT-configured ground-penetrating radars over heterogeneous grounds
(IEEE, 2001) Oǧuz, Uğur; Gürel, Levent
The simulation of transmitter-reciever-transmitter (TRT) configured ground-penetrating radars over heterogeneous grounds was discussed. The finite-difference time-domain (FDTD) methods along with the perfectly-matched layer (PML) absorbing boundary conditions (ABC) were used for the simulations. Scattered-field image demonstrated that the buried target was easily detected when buried in a homogenous ground. Results show that the TRT-configured GPR is sensitive to surface roughness and the main source of noise is the detoriorations in the ground-air interface.
Open Access
Simulations of ground-penetrating radars over lossy and heterogeneous grounds
(IEEE, 2001) Gürel, Levent; Oğuz, U.
The versatility of the three-dimensional (3-D) finite-difference time-domain (FDTD) method to model arbitrarily inhomogeneous geometries is exploited to simulate realistic groundpenetrating radar (GPR) scenarios for the purpose of assisting the subsequent designs of high-performance GPR hardware and software. The buried targets are modeled by conducting and dielectric prisms and disks. The ground model is implemented as lossy with surface roughness, and containing numerous inhomogeneities of arbitrary permittivities, conductivities, sizes, and locations. The impact of such an inhomogeneous ground model on the GPR signal is demonstrated. A simple detection algorithm is introduced and used to process these GPR signals. In addition to the transmitting and receiving antennas, the GPR unit is modeled with conducting and absorbing shield walls, which are employed to reduce the direct coupling to the receiver. Perfectly matched layer absorbing boundary condition is used for both simulating the physical absorbers inside the FDTD computational domain and terminating the lossy and layered background medium at the borders.
Open Access
Transmitter-receiver-transmitter configurations of ground-penetrating radar
(Wiley-Blackwell Publishing, Inc., 2002) Gürel, Levent; Oğuz, U.
Three-dimensional ground-penetrating radar (GPR) geometries are simulated using the finite difference time domain (FDTD) method. The GPR is modeled with a receiver and two transmitters with arbitrary polarizations in order to cancel the direct signals emitted by the two transmitters at the receiver. This GPR configuration is used to simulate scenarios involving single or multiple targets with arbitrary sizes. The buried objects are modeled as cylindrical disks. Perfectly matched layer absorbing boundary conditions are used to terminate the layered FDTD computational domain.
Open Access
Transmitter-receiver-transmitter-configured ground-penetrating radars over randomly heterogeneous ground models
(Wiley-Blackwell Publishing, Inc., 2002) Gürel, Levent; Oğuz, U.
Ground-penetrating radar (GPR) problems are simulated using the finite-difference time-domain (FDTD) method. The GPR model is configured with arbitrarily polarized three antennas, two of which are transmitting antennas fed 180° out of phase. The receiver is placed in the middle of two transmitters, where it receives no direct coupling from the transmitting antennas. The ground is modeled as a dielectric, lossy, and heterogeneous medium. The performances of the transmitter-receiver-transmitter-configured GPRs above the heterogeneous ground models are investigated. The computational domain is terminated by perfectly matched layer (PML) absorbing boundaries. The PML is adapted to match both air and ground regions of the computation space.