92 research outputs found
Quantifying Volume Changing Perturbations in a Wave Chaotic System
A sensor was developed to quantitatively measure perturbations which change
the volume of a wave chaotic cavity while leaving its shape intact. The sensors
work in the time domain by using either scattering fidelity of the transmitted
signals or time reversal mirrors. The sensors were tested experimentally by
inducing volume changing perturbations to a one cubic meter mixed chaotic and
regular billiard system. Perturbations which caused a volume change that is as
small as 54 parts in a million were quantitatively measured. These results were
obtained by using electromagnetic waves with a wavelength of about 5cm,
therefore, the sensor is sensitive to extreme sub-wavelength changes of the
boundaries of a cavity. The experimental results were compared with Finite
Difference Time Domain (FDTD) simulation results, and good agreement was found.
Furthermore, the sensor was tested using a frequency domain approach on a
numerical model of the star graph, which is a representative wave chaotic
system. These results open up interesting applications such as: monitoring the
spatial uniformity of the temperature of a homogeneous cavity during heating up
/ cooling down procedures, verifying the uniform displacement of a fluid inside
a wave chaotic cavity by another fluid, etc.Comment: 13 pages, 13 figure
Absorbing cross section in reverberation chamber: experimental and numerical results
Reverberation chamber (RC) test facility allows to determine the absorbing cross section (ACS) of lossy materials under a random field excitation. Measurements are based on the quality factor variation produced by the sample under test presence with respect to the empty chamber condition. Simulations are based on the representation of the RC electromagnetic field by means of a random plane wave superposition. A finite-difference time-domain code is used to compute the material absorbed power and to recover a numerical ACS. The method sensibility is stressed by application to small size samples. Comparison between numerical and experimental data reveals a satisfactory agreement. Results for different materials are presented in the paper: soft foam absorbers, carbon foam sheets, and carbon/carbon sheets
FDTD Full Wave Simulations of Reconfigurable Intelligent Surfaces
This paper presents the analysis of metasurfaces, here called reconfigurable
intelligent surface. The analysis is performed by numerical simulations that
implement the finite-difference time-domain method. The metasurface has been
modeled by metallic patches interconnected by varactor diodes. The
electromagnetic source consists of randomly generated plane wave. This kind of
analysis allows us to investigate the response of the metasurface when it is
hit by a random source.Comment: Accepted in EMC Europe 202
Near Field Optimization Algorithm for Reconfigurable Intelligent Surface
Reconfigurable intelligent surface (RIS) is a type of wireless communication
technology that uses a reconfigurable surface, such as a wall or building that
is able to adjust its properties by an integrated optimization algorithm in
order to optimize the signal propagation for a given communication scenario. As
a reconfiguration algorithm the multidimensional optimization of the GNU
scientific library was analyzed to evaluate the performance of the smart
surface in the quality of signal reception. This analysis took place by means
of electrodynamic simulations based on the finite difference time domain
method. Through these simulations it was possible to observe the efficiency of
the algorithm in the reconfiguration of the RIS, managing to focus the
electromagnetic waves in a remarkable way towards the point of interest.Comment: Accepted to URSI GASS 202
Base-case model for measurement uncertainty in a reverberation chamber including frequency stirring
We address the uncertainty of reverberation chamber (RC) measurements in presence of both mechanical and frequency stirring (FS). A base-case model is derived for reverberation fields affected by the measurement uncertainty due to the lack of a perfect statistical uniformity of fields in a RC. It is found that the measurement uncertainty associated with the FS depends on both the total uncorrelated samples and the local insertion loss (IL). The local IL depends on the frequency stirring bandwidth (FSB). The model allows us for obtaining separate measurement uncertainty contributions. Measurements support the achieved uncertainty model. In particular, results show that the dependence on the IL is normally rather weak also when very wide FSBs are used
Performance of parallel FDTD method for shared- and distributed-memory architectures: Application tobioelectromagnetics
This work provides an in-depth computational performance study of the parallel finite-difference time-domain (FDTD) method. The parallelization is done at various levels including: shared- (OpenMP) and distributed- (MPI) memory paradigms and vectorization on three different architectures: Intel's Knights Landing, Skylake and ARM's Cavium ThunderX2. This study contributes to prove, in a systematic manner, the well-established claim within the Computational Electromagnetic community, that the main factor limiting FDTD performance, in realistic problems, is the memory bandwidth. Consequently a memory bandwidth threshold can be assessed depending on the problem size in order to attain optimal performance. Finally, the results of this study have been used to optimize the workload balancing of simulation of a bioelectromagnetic problem consisting in the exposure of a human model to a reverberation chamber-like environment
Latest developments on the shielding effectiveness measurements of materials and gaskets in reverberation chambers
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