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The propagation of electromagnetic waves in a closed domain with a reflecting boundary amounts, in the eikonal approximation, to the propagation of rays in a billiard. If the inner medium is uniform, then the symplectic reflection map provides the polygonal rays' paths. The linear response theory is used to analyze the stability of any trajectory. The Lyapunov and reversibility error invariant indicators provide an estimate of the sensitivity to a small initial random deviation and to a small random deviation at any reflection, respectively. A family of chaotic billiards is considered to test the chaos detection effectiveness of the above indicators. [ABSTRACT FROM AUTHOR]

In this work, we present a 2 × 2 near-field multi-input multiple-output (MIMO) prototype for bit-error-rate (BER) and error vector magnitude (EVM) measurements in a metal enclosure. The near-field MIMO prototype was developed using software-defined-radios (SDRs) for over-the-air transmission of QPSK modulated baseband waveforms. We checked the near-field MIMO BER and EVM measurements in three different scenarios in a highly reflecting metal enclosure environment. In the first scenario, the line-of-sight (LOS) communication link was investigated when the mode stirrer was stationary. In the stationary channel conditions, near-field MIMO BER and EVM measurements are performed. In the second scenario, BER and EVM measurements were performed in dynamic channel conditions when the mode stirrer was set to move continuously. In the third scenario, LOS communication near-field MIMO BER and EVM measurements were performed in stationary channel conditions but now in the presence of MIMO interference. In three different scenarios, near-field MIMO BER and EVM measurements were investigated at different Tx USRP gain values and in the presence of varying levels of MIMO interference. [ABSTRACT FROM AUTHOR]

In this article, we will show how to improve the standard procedure in the Annex G of IEC 61000-4-21 on the shielding effectiveness (SE) of materials and gaskets through measurements performed in reverberation chambers. We thoroughly analyze and discuss measurement models (MMs), which are already present in the literature including the standardized model. Moreover, we further derive one of these MMs in a different way and introduce a different application, which is suitable to measure high SE values. We apply such MMs and compare results. By the analysis, discussion, and comparisons of measurement results, we clearly provide a robust improvement to the standard measurement procedure. [ABSTRACT FROM AUTHOR]

Global and local multitrace formulations (MTFs) provide a flexible and efficient method for the modeling of scattering and transmission of time harmonic electromagnetic (EM) waves by composite structures. This contribution extends the domain of applicability of global MTFs to cases where penetrable domains, perfectly conducting domain, and perfectly conducting thin sheets are all part of the design. A novel and easy to implement resonance-free equation to model scattering by perfect conductors is introduced. A Calderón preconditioner designed to limit the number of iterations required for the solution of the discrete system is designed and studied. The accuracy, flexibility, and efficiency of the method are demonstrated on a representative range of examples. [ABSTRACT FROM AUTHOR]

The paper focuses on the reverberation chamber method for the shielding properties evaluation of equipment-level enclosures. The enclosure under test is numerically modeled by an in-house finite-difference time-domain code that is able to predict the field inside the enclosure and the voltage captured by the probe placed inside it. The chamber fields have been modeled by applying the plane-wave superposition. The code is validated by measurements in our reverberation chamber. Subsequently, the effect of probe positioning and length on the induced voltage is analyzed. Finally, the enclosure shielding effectiveness is evaluated by applying two different definitions, and a statistical analysis is carried out, thus allowing an estimation of the measurement uncertainty. Index Terms--Finite-difference time domain (FDTD), frequency stirring, plane-wave superposition, reverberation chamber, shielding effectiveness, small enclosures.

We present the basic prerequisites of electromagnetism in flat space–time and provide a description of electromagnetism in terms of the Faraday tensor. We generalize electromagnetic theory to a relativistic setting, introducing the Einstein field equations to describe the propagation of electromagnetic radiation in curved space–time. We investigate the gravitational redshift and derive formulae for the combined effect of the gravitational redshift and the Doppler shift in curved space–time. [ABSTRACT FROM AUTHOR]

This paper presents a study of coupling between an external field and a metallic enclosure with a long aperture in the frequency range which includes several box resonances. A reverberation chamber (RC) and an anechoic chamber (AC) are considered as a field generation structure. In both cases, a customized FDTD code is used to calculate the current induced by the external field in a loop placed inside the enclosure. In order to simulate the AC facility, a single plane wave is used to represent the test field, whereas for the RC, the field is represented by a proper superposition of random plane waves. Numerical results are experimentally validated. The proposed method is useful to investigate the performance of the enclosure during its early design stage before the realization of a prototype. Index Terms--Anechoic chambers (AC), FDTD methods, immunity, reverberation chambers (RC).

We present a novel and flexible method to optimize the phase response of reflective metasurfaces (MSs) toward the desired scattering profile. The scattering power is expressed as a spin-chain Hamiltonian using the radar cross section (RCS) formalism. For MSs reflecting an oblique plane wave, an Ising Hamiltonian is obtained. Thereby, the problem of achieving the scattering profile is recast into finding the ground-state solution of the associated Ising Hamiltonian. To rapidly explore the configuration states, we encode the Ising coefficients with quantum annealing (QA) algorithms, taking advantage of the fact that the adiabatic evolution efficiently performs energy minimization in the Ising model. Finally, the optimization problem is solved on the D-Wave 2048-qubit quantum adiabatic optimizer machine for binary phase as well as quadriphase reflective MSs. Even though the work is focused on the phase modulation of MSs, we believe this approach paves the way to fast optimization of reconfigurable intelligent surfaces (RISs) that are modulated in both amplitude and phase for multi-beam generation in and beyond 5G/6G mobile networks. [ABSTRACT FROM AUTHOR]

The IEC 61000-4-21 and IEEE 299.1 documents report similar but not equal procedures to measure the shielding effectiveness (SE) of enclosures through the use of reverberation chambers. In this article, it is shown that these two measurement procedures can be merged in a single, enhanced, one. In particular, it is shown that the evaluation of the SE of enclosure in Annex H of IEC 61000-4-21, which exploits only mechanical stirring, can be improved by using the hybrid stirring, which includes also the frequency stirring, thus increasing the number of uncorrelated samples. On the other hand, it is shown that at low frequencies the evaluation of the SE of enclosures based on the definition in IEEE 299.1 can be improved through the use of the maximum values of measured powers rather than the average ones. The single, enhanced, proposed procedure provides more prudent SE values than the two standards at the low frequencies, especially for standard IEEE 299.1. The presented measurement approach is supported by results obtained in three different laboratories. [ABSTRACT FROM AUTHOR]

We describe the contribution of diffractive orbits to semiclassical approximations of Wigner function propagators. These contributions are based on diffractively scattered rays used in the geometrical theory of diffraction (GTD). They provide an extension of well-established approximations of Wigner-function propagators based on rays that propagate by specular reflection and refraction. The wider aim of this approach is to allow for diffractive mechanisms to be accounted for in Eulerian approaches to ray-tracing simulations. Such approaches propagate densities of rays rather than follow rays individually. They promise to be a more efficient means of performing ray-tracing simulations in complex environments with applications in, for example, planning of wireless signal coverage for mobile communication networks. [ABSTRACT FROM AUTHOR]

The next generations of wireless networks will work in frequency bands ranging from sub-6 GHz up to 100 GHz. Radio signal propagation differs here in several critical aspects from the behaviour in the microwave frequencies currently used. With wavelengths in the millimetre range (mmWave), both penetration loss and free-space path loss increase, while specular reflection will dominate over diffraction as an important propagation channel. Thus, current channel model protocols used for the generation of mobile networks and based on statistical parameter distributions obtained from measurements become insufficient due to the lack of deterministic information about the surroundings of the base station and the receiver-devices. These challenges call for new modelling tools for channel modelling which work in the short-wavelength/high-frequency limit and incorporate site-specific details—both indoors and outdoors. Typical high-frequency tools used in this context—besides purely statistical approaches—are based on ray-tracing techniques. Ray-tracing can become challenging when multiple reflections dominate. In this context, mesh-based energy flow methods have become popular in recent years. In this study, we compare the two approaches both in terms of accuracy and efficiency and benchmark them against traditional power balance methods. [ABSTRACT FROM AUTHOR]

This work presents over-the-air (OTA) performance, near-field bit-error-ratio (BER), and error vector magnitude (EVM) measurement using software-defined radio (SDR) in the mode-stirred metal enclosure at 5.8 GHz. The metal enclosure is stirred at 5.8 GHz using metallic paddle rotating with uniform speed. Paddle rotation creates a uniform electromagnetic field in the metal enclosure. The electromagnetic field environment in the metal enclosure can be controlled by loading the cavity with absorbing material. Field absorption can be different depending on the amount of absorbing material and location of the absorbers in the metal enclosure. It is shown that signal attenuation increases as we increase the number of absorbers. BER and EVM are measured in this environment and the performance of SDR based digital receiver is analyzed in this environment at RF frequency of 5.8 GHz. [ABSTRACT FROM AUTHOR]

The effect of a perfectly conducting planar boundary on the average linear momentum (LM), angular momentum (AM), and their power of a time-harmonic statistically isotropic random field is analyzed. These averages are purely imaginary, and their magnitude decreases in a damped oscillatory manner with distance from the boundary. At discrete quasi-periodic distances and frequencies, the average LM and AM attain their free-space value. Implications for the optimal placement or tuning of power and field sensors are analyzed. Conservation of the flux of the mean LM and AM with respect to the difference of the average electric and magnetic energies and the radiation stresses via the Maxwell stress dyadic is demonstrated. The second-order spatial derivatives of differential radiation stress can be directly linked to the electromagnetic energy imbalance. Analytical results are supported by Monte Carlo simulation results. As an application, performance-based estimates for the working volume of a reverberation chamber are obtained. In the context of multiphysics compatibility, mechanical self-stirred reverberation is proposed as an exploitation of electromagnetic stress. [ABSTRACT FROM AUTHOR]

In this study, the authors present the latest developments on the measurements for the shielding effectiveness (SE) of gaskets and materials in reverberation chambers (RCs). A variant method, where the insertion loss of the fixture is achieved from the SE of the fixture with no sample in the aperture is found; it is appropriate for gaskets and for any flat material having a sufficiently high reflectivity at least on one side. A simple and usable condition under which the simplest method for the SE measurements of gaskets and materials in RCs can be used is also given, as well as particular cases where it can be directly applied are shown. This method, whose applicability is enhanced in this study, can be used for gaskets and any flat sample. Such developments simplify measurement setup and associated procedures. Comparisons of results support the methods for the SE measurements of gaskets and material in RCs shown in this study. [ABSTRACT FROM AUTHOR]

In this paper we show a procedure to measure the impedance mismatch of antennas by exploiting the Time Domain (TD) option available in usual VNAs. The procedure can be applied even in the presence of reflecting obstacles in the measurement scenario surrounding the antenna under test (AUT). It is shown that effective application of the procedure requires to fulfill a reduced number of constraints basically involving the distance of the AUT from the nearest obstacle, the response resolution to be set through the TD option of the VNA, and the length of the gating aperture to be applied to the received signal. The proposed measurement procedure is in principle applicable to any antenna. However, it is very easy and advantageous for antennas having short responses in the time domain, such as horn antennas, where the method can likely be applied to frequencies less than 500 MHz. Comparison between the results obtained from measurements performed inside an anechoic chamber (that is, in the absence of reflecting obstacles around the AUT), outside the anechoic chamber, and even inside a reverberation chamber, demonstrate the effectiveness of the proposed measurement procedure. [ABSTRACT FROM AUTHOR]

Reflection and transmission phenomena associated with high-frequency linear wave incidence on irregular boundaries between adjacent acoustic or electromagnetic media, or upon the irregular free surface of a semi-infinite elastic solid, are studied in two dimensions. Here, an 'irregular' boundary is one for which small-scale undulations of an arbitrary profile are superimposed upon an underlying, smooth curve (which also has an arbitrary profile), with the length scale of the perturbation being prescribed in terms of a certain inverse power of the large wave-number of the incoming wave field. Whether or not the incident field has planar or cylindrical wave-fronts, the associated phase in both cases is linear in the wave-number, but the presence of the boundary irregularity implies the necessity of extra terms, involving fractional powers of the wave-number in the phase of the reflected and transmitted fields. It turns out that there is a unique perturbation scaling for which precisely one extra term in the phase is needed and hence for which a description in terms of a Friedlander–Keller ray expansion in the form as originally presented is appropriate, and these define a 'distinguished' class of perturbed boundaries and are the subject of the current paper. [ABSTRACT FROM AUTHOR]

In this paper, we present an improved model of measurement standard uncertainty of the insertion loss in a reverberation chamber (RC), including frequency stirring. Differently from the previous model, the enhanced one does not require specific conditions on the parameter to be measured. Such an enhancement is applicable for all usable measurement conditions in RCs. Moreover, a majorant is derived, that is obtained under a weak condition on the coefficient of variation of the parameter to be measured. Results from measurements support the validity of both the proposed enhancement and the majorant. [ABSTRACT FROM AUTHOR]

Electromagnetic radiation from complex printed circuit boards can occur over a broad frequency bandwidth, ranging from hundreds of megahertz to tens of gigahertz. This is becoming a critical issue for assessment of EMC and interoperability as electronic components become more and more integrated. We use emissions from an enclosure with a single-slot aperture and equipped with operating electronics to exemplify and model such sources. Spatial correlation functions obtained from two-probe measurements are used both to characterize the source and to propagate the emissions. We examine emissions in the submicrowave frequency range, where evanescent decay dominates the measured correlation function at the distances measured. We find that an approximate, diffusion-like propagator describes the measured emissions well. A phase-space approach based on Wigner functions is exploited to develop this approximation and to provide enhanced understanding of the emissions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Modeling the electromagnetic radiation from modern digital systems—acting effectively as extended stochastic sources as part of a complex architecture—is a challenging task. We follow an approach here based on measuring and propagating field-field autocorrelation functions (ACFs) after suitable averaging. From the modeling side, we use the Wigner transform of the ACFs to describe random wave fields in terms of position and direction of propagation variables. An approximate propagator for the components of the radiated magnetic field is constructed for these ACFs based on a linear flow map. Field-field ACFs at the aperture level are obtained from scanning measurements of complex sources. Distance and spatial resolution of the scanning plane is less than a wavelength from the source plane to capture the imprint of evanescent waves in the near-field ACFs. Near-field scanning and efficient near-to-far-field propagation is carried out and compared with measurements. Results of this study will be useful to assist far-field predictions, source reconstruction, and emission source microscopy. [ABSTRACT FROM PUBLISHER]

We report a new planar antenna design in the shape of a diamond. The performance of the antenna design is initially obtained through simulation, then fabricated, and its performance evaluated through experiment. Experimental characterization of the diamond-shaped monopole antenna shows good agreement with simulation. In comparison with a simple monopole antenna, our diamond-shaped monopole antenna features smaller geometric footprint and displays a higher bandwidth at millimeteric wave frequencies. [ABSTRACT FROM AUTHOR]