Ramiro Serra

Bivariate Statistical Approach for “Good-but-Imperfect” Electromagnetic Reverberation

This paper presents novel theoretical probability density functions (PDFs) for the magnitude and phase of electromagnetic fields inside reverberation chambers (RC) operating in a “good-but-imperfect” regime. The derivation is based on considering two Gaussian random variables with mean values, variances, and correlation that are departed from the ideal assumptions. A bivariate approach using a complete joint Gaussian distribution of these variables is defined. Marginal distributions obtained by integration of a 2-D joint PDF are compared with theoretical PDFs for ideal situations, and significantly lower rejection rates are experienced for field data measured in real RCs. Additionally, these novel marginal PDFs are highly general since they are able to describe both ideal and nonideal stirred fields and reproduce other findings.

Wave Impedance in Reverberation Chambers

This letter concerns probability density functions of the complex impedance of fields in mode-stirred reverberation chambers. They are based on the electric- and magnetic-field statistics derived for ideal reverberation conditions. The implications of these distributions on electromagnetic compatibility measurements using reverberation chambers are also discussed.

Methodology for Coupling and Interference Prediction in Integrated-Circuit Substrates

This paper presents a methodology to evaluate different integrated-circuit substrate technology options in terms of interference coupling. It is based on the electromagnetic characterization of the different substrate configurations as radial multilayered dielectric lossy open waveguides and the selection of the propagation modes that effectively contribute to substrate coupling. In addition, attenuation patterns are obtained for different technologies, doping profiles, frequencies, and interference mechanisms in order to provide a tool for early interference prediction, electromagnetic compatibility performance evaluation and floorplan strategy definition.

Goodness-of-Fit Tests in Reverberation Chambers: Is Sample Independence Necessary?

Goodness-of-fit (GoF) tests are interesting tools to test the overmodedness of the field inside a reverberation chamber (RC). In the definition of GoF tests independent and identically distributed samples are required. In this study, we focus on the effect of partial data correlation on GoF tests. We analyze the sensitivity of the most common GoF tests used in electromagnetic compatibility. The results presented herein are based on numerical and experimental data. We show that most of GoF tests are insensitive to correlations up to rather high values depending on the type of GoF test chosen. Implications for practical applications are discussed.

Misleading issues that came up when calibrating the Alenia Aeronautica reverberation chamber

In this paper we present two misleading issues that masked the correct consideration of the lowest useable frequency when applying the IEC 61000-4-21 international standard to the Ale-nia Aeronautica reverberation chamber. Analysis of results showed some contradictions between theory and practical experience of RCs. Particularly, these issues were found to be the number of frequency points and the harmonic distortion produced by the amplifiers.

Reverberation chambers a la carte: An overview of the different mode-stirring techniques

Reverberation chambers (RC), a name inspired in room acoustics, are also known in literature as reverberating, reverb, mode-stirred or mode-tuned chambers. In their basic form, they consist of a shielded metallic enclosure, forming a cavity resonator, together with some mode-stirring mechanism. The main goal of such stirring mechanism is to generate an amplitude-varying electromagnetic field that is ideally statistically uniform.

Design, Characterization, and Application of Fast, Broadband, High-Dynamic Range, Three-Axis Field Strength Probes

Conventional field strength sensors use different detection methods, each having advantages and disadvantages. Modern signals in, for instance, wireless communication systems and radars use very complex modulation. Other signals, such as the ones often measured in reverberation chambers with mode stirring, are fast-varying with high dynamic range. Conventional probes struggle to give reliable measurement data in these situations, while the more expensive solutions based on optical-electric conversion and heterodyne receiver, are so costly that often only one component of the field is measured. The impact of conventional field strength probes when measuring (complex) modulated signals is discussed. Furthermore, this paper describes the design, fabrication, and characterization of fast, broadband, three-axis, and high-dynamic range probes. They have been designed for mapping the fast-changing electric field strength in complex electromagnetic environments such as reverberation chambers under mode-stirring operation.

“Good-but-Imperfect” electromagnetic reverberation in a VIRC

Novel theoretical probability density functions (PDF) of electromagnetic fields inside reverberation chambers operating in a “good-but-imperfect” regime have been recently reported. The present work reports on the application and assessment of these PDFs using a non-conventional type of reverberation chamber, namely the Vibrating Intrinsic Reverberation Chamber (VIRC). A vector network analyzer was used in order to measure the complex field components. An electrically short dipole antenna was used as a receiving antenna. Five thousand frequency points were taken ranging from 200MHz (undermoded regime) to 4 GHz (overmoded regime), so one measurement every 760 kHz was performed. For each frequency, 200 samples of the real and imaginary part of the field were measured. Measurements confirm the fact that the novel PDFs are able to describe the occurrence of anomalous statistics in the VIRC.

A One-Dimensional Interpretation of the Statistical Behavior of Reverberation Chambers

This work focuses on building a fairly simple yet physically appropriate 1D model for a reverberation chamber which claims to be able to analytically predict the statistical behavior of fields inside such a chamber, without forsaking to the benefits of deterministic models. The statistical properties of the fields are introduced either by varying the size of a 1D stirrer, or (in absence of it) by varying the cavity size itself. A validation analysis was made over 27 different experiments in order to assess the main effects of the frequency and of the stirrer size. The properties derived are in agreement with other theories and with measured results on real reverberation chambers.

Statistical Anisotropy in Imperfect Electromagnetic Reverberation

A probabilistic characterization is performed for a class of field anisotropy coefficients for local random electromagnetic fields. Isotropic stirring (ideal reverberation), anisotropic stirring (polarization bias), and incomplete stirring (line-of-sight coupling or direct illumination) are investigated individually. For small degrees of planar anisotropy or coupling, trapezoidal distributions are obtained, representing first-order departures from ideal rectangular distributions. Distributions for two definitions of total field anisotropy are found to be less sensitive than those for the individual planar anisotropies. The method and results are useful for the calibration and validation of reverberation chambers when field anisotropy requires a separate assessment. Theoretical results are compared to measured data in two chambers.