1,721,101 research outputs found
Theoretical and experimental investigations inside electromagnetic reverberation chambers
No full textAccuracy Evaluation of the Huygens Subgridding Method
No full textIn this work, an application of the recent Huygens Subgridding (HSG) method to
study lossy materials with the ̄nite-di®erence time-domain (FDTD) scheme is presented and
a related error analysis discussed. Achieved HSG results showed a good agreement with a full
higher-resolution reference guide for di®erent electrical parameter values, indicating a negligible
numerical dispersion on the transverse section. Moreover, the increasing decimation factor e®ect
has been investigated to evaluate the subgridding accuracy. Findings are of interest in the
numerical prediction of planar screens e®ectiveness, material parameters retrieval and microwave
spectroscopy
Numerical Modeling of the Reverberation Chamber Method for the Measurement of Material Absorbing Cross Section
No full textReverberation 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 (FDTD) 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. The simulation technique can be applied to study the absorbing properties of absorbers with arbitrary geometry during the early design stage
Reverberation chamber as a multivariate process: FDTD evaluation of correlation matrix and independent positions
Get PDFThis paper evaluates the mode-stirring effciency in terms
of uncorrelated positions of a mechanical stirrer operating inside a reverberation chamber (RC). The actual RC is simulated and viewed as a multivariate random process: the chamber field is sampled in a lattice of spatial points distributed uniformly over a volume of arbitrary dimensions. By adopting such a grid, the stirrer effciency is then
computed through the correlation matrix, accounting for the residual correlation between stirrer positions. The second-order statistics are calculated averaging over the sampling volume. Results are presented for two stirrers that move in both synchronous and interleaved mode. A comparison with the traditional circular correlation (CC) method, for the determination of the uncorrelated positions, is done showing how CC overestimates stirrer effciency
Electromagnetic Reverberation: The Legacy of Paolo Corona
No full textThis paper reviews some significant achievements in the research activity and academic career of Paolo Corona, with particular focus on electromagnetic reverberation theory and measurements. An annotated selection is presented for some of his celebrated publications as well as some lesser well-known unpublished works.Some of his recorded views on issues and directions for future research on reverberation chambers are also included
Correlation matrix methods to assess the stirring performance of electromagnetic reverberation chambers
Get PDF© 2018 The use of correlation matrices to evaluate the number of uncorrelated stirrer positions of electromagnetic reverberation chambers has widespread applications in electromagnetic compatibility. We present a review of recent methods based on multivariate correlation functions that relates statistical inhomogeneities in space (frequency) to the reduction of uncorrelated cavity configurations. Full wave finite-difference time domain simulations of an actual reverberation chamber are performed through an in-house parallel code. The efficiency of this code allows for capturing extensive inhomogeneous/anisotropic reverberation fields at frequencies close to the lowest usable frequency (LUF) of the chamber. The concept of effective independent position is revised in light of random sampling and a model-driven relation with the probability distribution of correlation matrix entries is used to take into account spatial (frequency) inhomogeneities. Driven by extensive simulation data, an empirical probability density function is found for the correlation matrix elements to be non-central t-student distributed with asymmetry increasing towards low frequencies
Determination of the Reverberation Chamber Stirrer Uncorrelated Positions by Means of the Spatial and Frequency Correlation Matrix
No full textThe uncorrelated stirrer positions of a reverberation chamber are computed by means of Pearson's correlation matrix. Two methods are adopted to populate the matrix, and results are compared with those given by standard method. The former uses the total electric field magnitudes sampled in a large spatial lattice in the working volume for each stirrer position. The latter uses the same quantity sampled within a frequency band for a single point in the working volume for each stirrer position. Results returned by the two methods are compared for a large chamber equipped by a rotating carousel stirrer
ANALYSIS OF THE ENTROPY IN FAST TIME DOMAIN SIMULATIONS OF REVERBERATION CHAMBERS
No full textIn this contribution, we investigate the entropy growth in a mode-stirred cavity simulated by the FDTD method. The adopted reverberation chamber is efficiently stirred by paddles and excited by a Gaussian pulse. It is observed that the entropy starts growing quadratically in time, then it increases linearly during the energy buildup, and it saturates after a few nanoseconds, when the onset of disordered fields occur. This allows for terminating the numerical simulations well before the Richardson time, as the asymptotic entropy is rapidly achieved. The analysis is based on the eigenvalues of the correlation matrix, calculated over a dense grid of spatial points, thus supporting the perspective of the reverberation chamber as a statistical multivariate process
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