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International audience; In this article, we introduce a method to exploit ultra-high dielectrophoresis (UHF-DEP) with a microfluidic radio frequency device able to sort biological cells by deflecting the trajectory of the targeted population in a continuous flow. This study highlights the capability of a high frequency lab-on-chip implemented UHF-DEP cytometer to isolate cancer stem cells (CSCs). Actually, CSCs sorting by an efficient, fast and low-cost method remains an issue. Above 20 MHz, the intracellular dielectric properties of cells determine the dielectrophoretic behavior of cells and is then very sensitive to the cell cytoplasm content. The proposed cell sorting principle exploits the combination of the fluidic drag and the repulsive dielectrophoretic forces in order to isolate CSCs hidden within differentiated cancer cells. We previously demonstrated the UHF-DEP behavior of cells, as a new type of electromagnetic biomarkers to discriminate cancer stem cells among a tumor population from colorectal cancer cell line.

International audience; The Spectral FDTD (SFDTD) method is combined with the discrete-time time-domain vector fitting algorithm (TDVFz) to analyze 3D periodic structures excited by oblique incident plane waves over a wide frequency band. The time signal reconstruction with TD-VFz produces an untruncated responseover an infinite time window allowing an accurate spectral result, specially near the cut-off frequency separating the spectrum propagating wave region of evanescent wave region

International audience; This article deals with robust fixed-time stability and stabilization. First, new global robust fixed-time stability results are proposed for scalar systems by using constant and variable exponent coefficients. Then, they are applied to global robust fixed-time stabilization of a class of uncertain nonlinear second order systems by using sliding mode control. All the results are illustrated in simulation.

This paper explores a new concept for the design of high scanning-range phased array antennas: the Interleaved Parasitic Arrays Antenna or IPAA. In this concept, we use periodic parasitic elements and the generator impedance to control the Active Voltage Standing Wave Ratio (AVSWR) over a wide scanning range. This new array architecture comes with a design methodology enabling a smooth step-by-step design process aiming at reducing the need for full-wave calculations. First, a numerical dual-polarization design is presented in detail to illustrate the methodology and to give the design keys to the reader. Then, a prototype working in the 5G C-band between 3.4 and 3.8 GHz (11% bandwidth) was designed using this methodology and measured for a 36-element array. It is meant to demonstrate and validate the mutual coupling management done by the interleaved parasitic arrays and the design process accuracy. Good correspondence between measurements and simulation was found and the proposed unit cell with its corresponding tile can be integrated in a larger phased array with active modules to perform beam steering over an important scanning range without deteriorating the AVSWR. The proposed unit cell is designed for a high-scanning range going from $\theta =0^{\circ }$ to $\theta = 70^{\circ }$ for every $\varphi $ -directions and shows an active reflection coefficient for an infinite array below −13.6dB.

International audience; This paper provides a practical control solution to remote control systems with unknown time-varying delays. An external signal which can be considered as a specific communication loop is added to estimate the unknown round-trip delay in finite time. Then the system is stabilized with the practical delay estimation technique and a predictor-based controller. The main results of this paper also provide an alternative way to design predictor-based controller for systems with known input and output time-varying delays. The theoretical results of this paper are illustrated by simulation results.

Communications inside an aircraft cockpit are currently based on wired connections especially for the audio headsets used by the pilots. A wireless headset would be an advantage in terms of comfort and flexibility but the use of classical radio frequencies is limited by interference and security issues. Optical wireless communication technology is an option for headset connectivity. Indeed, as optical beams are confined, this technology provides robustness against the risk of hacking, thus increasing security. In addition, the use of optical waves ensures the absence of radio-frequency disturbances. Using simulation, this article presents a thorough study of the optical wireless channel behavior inside the cockpit of an aircraft by considering a headset worn by a pilot possibly in motion and an access point at the ceiling. The impact of the characteristics of the environment model, such as the level of geometric description, the reflectivity of materials and for the first time, the ambient noise induced by the sun, is highlighted. System performance is evaluated in terms of optimal half-power angles and the necessary optical power of the light sources.

Accurately estimating the parameters of a gray-box linear time-invariant state-space representation is still a challenging problem especially if the number of unknowns exceeds ten. The standard nonlinear optimization-based procedures often fail because the initial guesses are not in the domain of attraction of the user-defined cost function global minimum. Herein, a new solution is developed to give access to estimated parameters which are accurate estimates of the unknown parameters directly or, at worst, good initial guesses for any standard nonlinear optimization-based method. By assuming that 1) the gray-box model to identify is minimal and structurally identifiable, 2) the parameter dependency is affine, and 3) the available datasets have been transformed into a reliable and accurate black-box state-space model, our procedure consists in determining the unique similarity transformation between the black-box and gray-box representations of the system to identify. More specifically, we introduce a technique which first extracts a system of equations linear in terms of the similarity transformation; second, it solves this system by using standard linear algebra tools; finally, completes this two-step procedure by a numerical optimization solution (dedicated now to a very small number of unknowns) if the second step does not give access to all the similarity transformation parameters effectively. In this contribution, we first describe our new procedure, prove its capabilities of giving accurate estimates under specific practical constraints, and finally demonstrates its effectiveness with simulation examples.

A temperature-compensated resonator based on stacked rings is proposed in this letter. The resonator is made of several layers of machined dielectric substrates where the copper rings stand. These rings define an air-filled TE011 cavity with an unloaded quality factor better than 1800. Due to a low sensitivity of the air gap between the layers and metallic contact of the TE011 mode, a cavity with low building constraints (no vias and no connection between layers) is realized. Furthermore, a multilayer design allows the introduction of a controlled amount of dielectric material in the cavity with a negative thermal coefficient of permittivity to realize temperature compensation of the device and to counteract its natural thermal expansion. Thus, this compensation layer allows proper management of a frequency drift from of −18 to +18 MHz for a temperature range of 20 °C–80 °C. However, there is a tradeoff, and the quality factor decreases as the compensated layer is inserted. A guideline demonstrating the performance of the design and the compensation technique is thus presented in this letter.

This paper presents a fastening assemblies FDTD model based on a lumped element circuit integrated into thin wire formalism. It can be used to quantify current dispersion or extreme current in aircraft fuel tank fasteners and to optimize the lightning protection in hotspot zones. An original method allows the characterization of the fastener lumped resistances. This method dealing with dc measurement and an optimization process is validated provided that 1) the measurements number is greater than the lumped elements number and 2) each node of the circuit is used at least once. Due to the large uncertainties from one fastener to the other one in the same family, the circuit model is supplement with a statistical model using the results about the fastener resistances state after a lightning shot presented in part I. Stochastic distribution values are applied to each lumped resistance of the fastener circuit model. Making a hybridization between a circuit solver and the finite difference time domain (FDTD) method, the circuit model is added in the same three-dimensional FDTD generic fuel tank modeling as presented in part I. Comparing the current distributions of the simple model of the part I and the circuit model, the uncertainties introduced by each model are presented.

The latest video coding standard, High Efficiency Video Coding (HEVC), uses quarter-pixel motion vector (MV) resolution for motion compensation. The adaptation of MV resolution supported by progressive MV resolution (PMVR) brings further improvement to performance by progressively adjusting the resolution according to the distance between the MV and its predictor. However, progressive adjustment of resolution by PMVR does not consider the inherent characteristics of the coding block. In this paper, we propose several ways to improve PMVR. First, we show that the performance of PMVR is correlated with the spatiotemporal characteristics of the video sequence. Then, to cope with the limitations of PMVR, we propose a flexible framework for the adaptation of MV resolution using: 1) PU size and gradient; 2) PU size, gradient, and MV components; and 3) PU size and spatiotemporal characteristics of the frames. Finally, a smart motion estimation around multiple MV predictors is performed to take full advantage of the proposed scheme. The proposed tools are implemented on top of HM-16.6. Extensive experiments and comparison with HEVC show 1.3%, 2.7%, and 1.0% average BD-Rate savings for random access, low-delay P, and low-delay B configurations, respectively.

International audience; We report on a comprehensive analysis of the polarization-maintaining behavior of two different kinds of inhibited-coupling guiding hollow-core fibers and the influence of fiber bends. A phase shift induced degradation of the incident linear polarization state was observed due to a mismatch of the propagation constants of the orthogonally polarized LP01-modes of the fiber. This effect was predicted theoretically and is corroborated with numerical simulations and experimental results. It is shown that the phase shift is enhanced by a reduction of the bending radius of the fiber, but can be circumvented by orienting the polarization of the injected beam either parallel or perpendicular to the plane of bending.

In this paper, we characterize the signature of traps existing in the new AlGaN/GaN HEMT of 0.15- $\mu \text{m}$ ultrashort gate length and $8 \times 50\,\,\mu \text{m}^{2}$ gate width (GH15) through three different measurement techniques which are low frequency (LF) S-parameters, drain-current deep level transient spectroscopy (I-DLTS), and LF drain noise characterization. These three different measurements techniques were performed for varying chuck temperatures ( $T_{\mathrm {chuck}}$ ) ranging between 25 °C and 125 °C and for the same biasing condition. All measurements ensure approximatively the extraction of the same signature of traps [apparent activation energy ( $E_{a}$ ) and cross section ( $\sigma _{n}$ )] existing in the UMS device. Furthermore, we have characterized the thermal resistance ( $R_{\mathrm {TH}}$ ) using pulsed $I$ – $V$ measurement and a two-step calibration process. The determination of $R_{\mathrm {TH}}$ is important to evaluate the device and to know precisely the signature of traps $E_{a}$ and $\sigma _{n}$ defined by the Arrhenius equation. A large signal measurements using an unequally spaced multitone (USMT) signal were done in order to evaluate the performance of GH15 transistor around the optimum load impedance in terms of efficiency (max PAE ~ 55%). The leakage current which measured before and after all measurements for $V_{\mathrm {GS}} = -6$ , −7 V and for $V_{\mathrm {DS}}$ varying from 0 to 10 V was lower than $100~\mu \text{A}$ /mm. To our knowledge, results on charge-trapping and large-signal performance are reported for the first time in 0.15- $\mu \text{m}$ technology.

Most multimedia source encoders produce scalable bit streams that are vulnerable to noisy channel effects. Unequal error protection (UEP) designs are attractive solutions for such scalable bit streams. In the other hand, the structure of multiple concatenated codes, which consist of the combination of two or more elementary encoders and interleavers, offers a flexible implementation of unequal data protection. To provide an efficient protection for embedded source bit streams, an adaptive concatenated coding/decoding design is proposed in this paper inspired by serially concatenated turbo codes. This scheme involves iterative decoding of concatenated codes for JPEG 2000 image transmission. In the case of time varying channels, the concatenated coding rates are adaptively chosen to maximize the visual quality. The simulation results show that the proposed scheme achieves better image quality improvements at the receiver side compared with a conventional multiple turbo codes-based design, with significant peak-signal-to-noise ratio gains.

This letter presents the design and fabrication of a 287-GHz resonator and a bandpass filter. The fabrication is conducted using an additive microfabrication process, based on successive photolithography and metal electroplating steps. This process has allowed the fabrication of a single-cavity resonator and a 3.5% relative bandwidth two-pole bandpass filter. The cavity has a measured unloaded $Q$ of 137, and the filter has a measured loss of 4.6 dB and matching better than 20 dB in very good agreement with E-M simulation results.

We present the accurate modeling and analysis, followed by experimental validation, of a 1024-element (64-by-16) antenna array. This fixed-beam array radiates linear polarization in Ka-band (19.7–20.2 GHz). It acts as a first step in the design and modeling of future antenna arrays for satcom-on-the-move applications. Accurate prediction of the behavior of such a large array is a challenging task since full-wave simulation of the entire structure cannot be considered. By taking advantage of existing formalisms on periodic arrays and by using appropriate methods to efficiently exploit such formulations, it is possible to accurately define the performances of all building blocks, from the feeding circuits to the radiating elements, over a frequency range. Such a detailed design also allows an accurate physical analysis. It has been successfully used to guarantee the measured performances. This paper is intended to detail different steps to antenna designers.

In this paper, a new sensor system for simultaneous and independent multipoint strain and temperature measurements is presented. The interrogation of the sensing heads has been carried out by monitoring their FFT phase variations. In particular, two of each microstructured optical fiber (M0F) cavity interference frequencies were used for the measures. This method is independent of the signal amplitude and also avoids the necessity of tracking the wavelength evolution in the spectrum, which can be a handicap when there are multiple interference frequency components with different sensitivities. The sensing heads present birefringent and multimodal properties and therefore both characteristics lead to their own interference with different properties and sensitivities. The multiplexing capability of the sensing heads and the interrogator method has also been tested and validated. Sensors were operated within a range of temperature 30°C-80°C and a deformation of ̴450 με was applied. Crosstalk between measurements can be corrected through simple math operations leading to independent and crosstalk-free multipoint and multiparameter sensors. This work was supported in part by the Spanish Comisi´on Interministerial de Ciencia y Tecnolog´ıa within projects TEC2016-76021-C2-1-R and TEC2013-47264-C2-2-R, in part by Cost action MP1401, and in part by FEDER funds from the European Union.

We propose and demonstrate the first single channel real-time microwave photonics digital beamforming radar imaging system based on a silica photonics summator. Considering a set of microwave signals received by an antenna array, the number of receiving chains is concentrated into a single channel by achieving an analog time-division multiplexing of radio frequency modulated optical signals using well-calculated optical fiber lengths and a microwave photonics summator. This single channel output guarantees a simplified architecture and minimizes the required number of analog-to-digital converters. A fixed fiber length difference is implemented to introduce a true time delay between each channel in order to time interleave them. The image of the scenes is then retrieved by demultiplexing the received signal and applying digital beamforming techniques. The potential applications of this structure are to implement in a short-range radar imaging system.

We investigate the use of a dynamic metasurface as the transmitting antenna for a synthetic aperture radar (SAR) imaging system. The dynamic metasurface consists of a 1-D microstrip waveguide with complementary electric resonator (cELC) elements patterned into the upper conductor. Integrated into each of the cELCs are two diodes that can be used to shift each cELC resonance out of band with an applied voltage. The aperture is designed to operate at $K$ -band frequencies (17.5–20.3 GHz). We experimentally demonstrate imaging with a fabricated metasurface aperture using well-known SAR modalities, showing image quality comparable to traditional antennas. The agility of this aperture allows it to operate in spotlight and stripmap SAR modes, as well as in a third modality inspired by computational imaging strategies. We describe the dynamic metasurface antenna’s operation in detail, demonstrate high-quality imaging in both 2-D and 3-D, and examine various tradeoffs governing the integration of dynamic metasurfaces in the future SAR imaging platforms.

International audience; This paper presents the design and a first evaluation of a new monitoring system based on contactless sensors to estimate sleep quality. This sensor produces thermal signals which have been used, at first, to detect a human presence in the bed and then to estimate sleep quality. To distinguish between different sleep phases, we have used methods of signal processing in order to extract the necessary features for learning an adapted statistical model. The existing monitoring systems use sensors attached to the bed or worn by the person. We propose in this paper a system based on a passive thermal sensor which has the advantage of being fixed on the wall, thus it is easier to use and more reliable. We explain different signal processing steps and describe sleep stage recognition algorithms. We propose an adaptation of the SAX method for the thermal signal. Finally, we evaluate our system in comparison with a polysomnographic recording system in the Hospital (CHU) of Limoges.

Recently, we have introduced a new approach based on Holland's formalism to deal with oblique thin wire in the finite-difference time-domain (FDTD) method. Here, we propose an original technique to model accurately dielectric coated thin wire, which can be freely inclined or shifted in the FDTD grid. In addition, the multiwire junction of oblique thin wire formalism is extended by means of a rigorous equivalent circuit diagram of the insulated wires. The approach facilitates complex modeling of cables embedded in lossy dielectric medium including buried insulated cables. It exhibits same accuracy as in integral equation method. However, the FDTD method shows better efficiency in time computational as soon as the application includes a soil or when increasing complexity and density of the modeling structure.

In this paper, the type, activation energy ( $\textit{E}_{a}$ ) and cross section ( ${\sigma }_{n}$ ) of the GaN buffer traps existing in the AlGaN/GaN high-electron mobility transistors are investigated through low frequency (LF) S-parameters measurements. Furthermore, we present the 2-D physics based TCAD numerical simulation analysis of this device. The dc simulation results are calibrated to match with the experimentally measured I–V characteristics and this allows to qualitatively estimate the concentration of traps ( $\textit{N}_{T}$ ) present in the GaN buffer. Knowing the measured trap energy level and the estimated trap concentration $\textit{N}_{T}$ , TCAD physical simulations are performed at various temperatures in order to extract the LF- $\textit{Y}_{22}$ admittance parameter. Interestingly, the LF- $\textit{Y}_{22}$ simulation results are found to be in good agreement with the measurements and this result strongly suggests that LF admittance dispersion is an effective tool in identifying the traps present in the GaN buffer. Moreover, this paper reveals that acceptor-like traps with an apparent concentration of $5.0\times 10^{16}$ cm $^{-3}$ and with the apparent trap energy level of 0.4 eV below the conduction band are located in the GaN buffer.

Conventional direct current arc plasma spray torches generate highly unstable plasma jets. This leads to some difficulties with control of coating properties especially when injecting liquid feedstock for the elaboration of finely structured coatings. At constant applied current, a properly designed arc plasma torch can work in self-sustained pulsed mode that produces large amplitude oscillations of the arc, which are interrupted by very repeatable restrikes. This paper investigates the influence of the modulation of the applied current on the arc stability. Electrical and acoustic diagnostics permit to show that amplification of arc oscillation and a stabilizing mechanism occur when the arc current frequency approaches the torch resonance frequency. Time-resolved optical emission spectroscopy is used to determine temperature and enthalpy profiles close to the resonance and the enthalpy modulation.

In this paper, we propose a new 3-D conservative FDTD(2, 4) scheme exhibiting properties close to the 2-D-M24 scheme. This scheme is designed to retain a 2-D stencil in the field update equations and has high-phase accuracy at low-grid resolutions. Moreover, an accurate Courant–Friedrichs–Lewy condition has been validated for this scheme. Some experiments are conducted to assess the higher accuracy of the proposed scheme.

On all continents, assessing efforts to make information and communication technologies available throughout a territory has become a necessity. As part of universal access and service, this paper aims at assessing the impact of radio access technologies on universal access indicator. To achieve this, a mathematical model has been developed to deal with locality coverage and broadband needs, based on a methodological approach consisting in integrating parameters linked to access index through radio technologies. This approach has been applied to a real case study of the state of Ouaddaï in Chad, which has contributed to highlight its relative simplicity of implementation.

International audience; The development and construction of self-scanning capability short-range ultrawideband (UWB) radar is forthcoming for the French Military for Defense. This paper is devoted to the presentation of the self-scanning radar principle and of the development, construction, and tests of the different blocks needed to implement the elementary part of the forthcoming radar. The elementary radiation source is composed of a microstrip line with photoconductive switches, an optical system to trigger the switches, a pulsed modulator used as bias voltage to load the line, and a UWB antenna to radiate high electric fields in a broad frequency band. The main proposed innovations are devoted to the integration of the photoconductive switches within the antenna and to the use of the pulsed modulator as bias source instead of a dc voltage source. This modulator allows considering the increase in the yield of the whole source as well as the increase in the radiation bandwidth. Experimental results are presented in order to compare the switching efficiency with a dc bias source against this pulsed modulator bias source. Finally, photoswitches triggered by an 80-ps/20-μJ laser source are able to generate monopolar or bipolar pulses in the kilovolt range with subnanosecond duration and a 33-MHz pulse repetition frequency. First radiated electric field results of the whole device are also reported. \textcopyright 2017 IEEE.

This paper presents an innovative and compact injection system able to extend the possibility to perform bulk current injection (BCI) tests until 2 GHz (at least). The proposed structure is a Stripline injection cell ensuring the propagation of a progressive transverse electromagnetic wave (TEM). Within the structure, the victim cable is exposed to a tangential electric field of high amplitude corresponding to the TEM wave. In order to illustrate the interest and the performances of the proposed setup, a generic device under test is built. Then, when comparing the performances of the proposed system with a reverberation chamber from an immunity test point of view, it is shown that the proposed setup obtains similar performance until 2 GHz, in particular when comparing the power required to obtain a failure of the device under test. Due to its simple geometry, the proposed injection system is easy to model with a full-wave EM solver and does not present any nonlinear effect, two important advantages in comparison to classical toroidal magnetic probes used in BCI tests.

The ultrafast speed and the large spatial area scanning autonomy are the two main advantages of the new radar presented in this paper. Indeed, the autonomous beam scanning capability with high pulse repetition frequency (PRF) is obtained by coherent combining of electrical fields emitted from active antennas’ array integrating photoconductive switching devices. An original signal processing associated with this new radar system is presented. We show a hybrid version of a CLEAN algorithm able to overcome the depth limitation induced by high PRF with standard imaging signal processing. Simulations and measurements are performed to validate the proper operation of the algorithm.

International audience; In this paper, a new characterization method, which allows the determination of the time constants of traps in AlGaN/GaN high electron-mobility transistors is proposed. The approach is based on the current transient method for assessing the time constants that are involved in real working conditions. To do that the dc filling pulses, which are classically used in this method, are replaced by RF filling pulses, which reproduce the real large-signal conditions. To investigate the impact of large-signal working conditions on the trapping phenomena, on-wafer single-pulse load–pull characterizations are carried out at different temperatures and for two different output load impedances: maximum of power-added efficiency and mismatched impedance. The results obtained show the deep impact of the load-line excursion on the current collapse of the detrapping drain current. A comparison between the single-pulse RF load–pull characterization and single-pulse dc measurement is finally presented.

International audience; This technical note deals with the study of uplink (from the mobile phone to the base station) transmitted power control in Long Term Evolution (LTE). It provides a nonlinear Potential Feedback Control (PFC) for scalar discrete-time systems with input delays and disturbances by using the Lyapunov theory and the Artstein transform. It is an original approach in which a stabilization problem of a linear scalar system with a constraint on the state space is transformed into a problem of nonlinear stabilization. We use this strategy of stabilization for the uplink transmission power control in LTE.

International audience; Distance functions are at the core of important data analysis and processing tools, e.g., PCA, classification, vector median filter, and mathematical morphology. Despite its key role, a distance function is often used without careful consideration of its underlying assumptions and mathematical construction. With the objective of identifying a suitable distance function for hyperspectral images so as to maintain the accuracy of hyperspectral image processing results, we compare existing distance functions and define a suitable set of selection criteria. Bearing in mind that the selection of distance functions is highly related to the actual definition of the spectrum, we also classify the existing distance functions based on how they inherently define a spectrum. Theoretical constraints and behavior, as well as numerical tests are proposed for the evaluation of distance functions. With regards to the evaluation criteria, Euclidean distance of cumulative spectrum (ECS) was found to be the most suitable distance function.

International audience; A simple and efficient analytical method has been developed for predicting the electromagnetic field coupling with a lossless transmission line (TL) located in a rectangular enclosure. The metallic enclosure is excited by an internal electrical short dipole or monopole source. The electric fields generated inside the rectangular enclosure and excited by some simple sources are calculated by using the electric-type dyadic Green's function. Our approach combines, on one hand, a lumped-pi circuit model of TL and, on the other hand, the Agrawal coupling model. A simple equivalent circuit has been derived which can give prediction for the coupling between the cavity field and the TL. This method is computationally less intensive compared to other numerical methods to solve such a problem. The analytical results have been successfully compared over a wide frequency band with the finite-difference time domain and experimental results carried out in different combinations of source and line position.

International audience; This letter presents a new type of E-band vertically aligned carbon nanotubes (VACNTs)-based air-filled waveguide (AFWG). This original concept is based on the use of bundle of VACNTs as equivalent WG’s metallic lateral walls. The WG is designed by applying a full-wave three dimensions electromagnetic software and an equivalent VACNTs bulk model. Then, the WG is fabricated using a CMOS compatible CNTs transfer process and a dedicated assembly process. For the first time, the concept of the CNTs-based AFWG is validated by measurements, and an experimental attenuation constant is estimated at 0.5 dB/mm between 81 and 86 GHz.

International audience; This letter presents a simple reconfigurable antenna concept, which is based on the influence of reflection phase shifters on the mutual coupling to the parasitic elements. The developed antenna operates in the Industrial, Scientific and Medical band (ISM) at frequency of 2.45 GHz. The objective of this work involves the development of a generic and low-cost reconfigurable antenna, with a 1-D or 2-D layout. The parasitic elements are loaded with varactor phase shifters, and the global synthesis is performed through different radiation pattern objectives. In this letter, we have limited these objectives to two opposite directions as we considered only a 1-D layout. The design has been manufactured and measured. A comparison between the measured and the simulation results shows a very good agreement.

International audience; This paper investigates the impact of irregular pulsed RF signals on the pulse-to-pulse (P2P) stability of a microwave power GaN HEMT amplifier. This study is based on both the time-domain envelope measurements and nonlinear circuit envelope simulations of P2P stabilities. Measurements and simulations are performed with an irregular pulse train that integrates a long silence (i.e., off-time) between each periodic burst of RF pulses because of its influence on temperature and trap behaviors of GaN HEMTs. The first aim is to experimentally characterize the impact of silence durations and output mismatching on the amplitude and phase P2P stabilities of a 10-W S-band GaN HEMT amplifier. The second objective is to assess the ability of nonlinear HEMT models to fit the time-domain measurements of pulse-to-pulse stabilities. This final part of the paper is focused on the relative impact of electro-thermal and drain-lag models on the nonlinear circuit envelope simulations of pulse-to-pulse stabilities. It is demonstrated that both the thermal and trapping effects have to be considered to fit the complex behavior of measured pulse-to-pulse stabilities for microwave GaN HEMT power amplifiers.

International audience; While determining the order as well as the matrices of a black-box linear state-space model is now an easy problem to solve, it is well-known that the estimated (fully parameterized) state-space matrices are unique modulo a non-singular similarity transformation matrix. This could have serious consequences if the system being identified is a real physical system. Indeed, if the true model contains physical parameters, then the identified system could no longer have the physical parameters in a form that can be extracted easily. By assuming that the system has been identified consistently in a fully parameterized form, the question addressed in this paper then is how to recover the physical parameters from this initially estimated black-box form. Two solutions to solve such a parameterization problem are more precisely introduced. First, a solution based on a null-space-based reformulation of a set of equations arising from the aforementioned similarity transformation problem is considered. Second, an algorithm dedicated to nonsmooth optimization is presented to transform the initial fully parameterized model into the structured state-space parameterization of the system to be identified. A specific constraint on the similarity transformation between both system representations is added to avoid singularity. By assuming that the physical state-space form is identifiable and the initial fully parameterized model is consistent, it is proved that the global solutions of these two optimization problems are unique. The proposed algorithms are presented, along with an example of a physical system.

In a recent paper, a novel technique that allows for the first time to perform actual antenna radiation pattern measurements in reverberation chamber (RC) has been presented. Even though its results were in good agreement with the ones obtained in anechoic chamber (AC), it was necessary to repeat stationary measurements locating the antenna under test (AUT) at N different fixed positions along its line-of-sight to a fixed probe antenna per angle under study, thus multiplying by N the measurement time when compared to measuring in AC. On the contrary, in this contribution, an improvement of this technique is presented, obtaining an antenna radiation pattern by performing only one measurement per angle under study, taking advantage of real-time Doppler effect. Moreover, the antenna gain is obtained from only one of these measurements, without the need to know the antenna efficiency, by using the Friis transmission equation. In order to demonstrate the validity of this improved technique, the radiation pattern for both E- and H- planes and the gain of a horn antenna have been measured in an RC, being the results in good agreement with the ones obtained in AC and the values provided by the antenna manufacturer, respectively.

Improvements of a methodology [1] able to compute the parasitic electromagnetic emissions of a solar panel are presented in this paper in order to handle real solar panels. Thus, the method is able to take into account solar panels with triple-junction solar cells, series or shunt power regulation system, and honeycomb composite panels. This numerical method is validated experimentally by comparing the near magnetic field emitted by a real solar panel and calculated by the method.

International audience; Rubidium vapor is loaded into hypocycloidal core shaped Kagome hollow-core photonic crystal fiber (HC-PCF) with the wall of its inner core coated with aluminosilicate ceramic (sol-gel). We show that the presence of Rb vapor is maintained for a longer duration when compared to uncoated Kagome HC-PCF. Rb vapor within the hollow-core of a sol-gel coated Kagome HC-PCF is preserved for over 500 h after the source of Rb is halted. And Rb vapor is detected in the sol-gel coated HC-PCF for more than 80 h after the background Rb vapor signal is no longer observed.

International audience; The steady expansion of the number of wireless devices and the ubiquity of the networks give rise to various interesting challenges for the future sixth generation (6G) of wireless communication systems. Particularly, the operators have to handle massive connectivity among Machine Type Devices (MTDs) and increasing demand for eMMB through limited spectrum resources. Non-Orthogonal Multiple Access (NOMA) has been spotlighted as an emerging technology to meet the above-mentioned challenges. In this paper, we consider a densely deployed network in which users are divided into NOMA coalitions. Firstly, we model the power allocation problem as a differential game. Then, we extend the formulated game using a Mean Field Game (MFG) theoretic framework by considering the effect of the collective behavior of devices. Furthermore, we derive a distributed power control algorithm that enables the users to appropriately regulate their transmit power according to brief information received from the BS. Indeed, the analysis of the proposed approach is governed by the two fundamental Hamilton- Jacobi-Bellman (HJB) and Fokker-Planck-Kolmogorov (FPK) equations. Numerical results are presented to analyze the equilibrium behaviors of the proposed power control algorithm and to demonstrate the effectiveness of the formulated MFG compared to existing works in the literature.

The equivalent cable bundle method (ECBM), able to highly reduce the complexity of complex cable networks in numerical modeling, is applied in this paper to cable bundles in the presence of complex ground structures. In this case, a fictitious perfectly conducting ground plane is considered instead the real ground structure during the ECBM process. The use of the ECBM method appears as a relevant solution for the modeling of real industrial cable networks when the multiconductor transmission line theory is not applicable and full-wave modelings of the nonsimplified cable networks are not possible for computation time reasons.

International audience; High-voltage (HV) ultrashort pulse technologies have found many applications in areas such as medicine, biology, food processing, environmental science and defense. Some applications are dependent on the pulse parameters such as duration, amplitude, shape, as well as the number of pulses applied and the frequency rate. Generators that can produce powerful electrical pulses with adjustable duration, amplitude and shape are convenient but still unusual. In this paper, we present and characterize a robust and versatile generator built on the frozen wave generator concept using photoconductive semiconductor switches. The results show that the generator can produce pulses of various shapes, peak-to-peak amplitudes up to 13.1 kV, maximum amplitudes of 6.9 kV and with durations in the nanosecond and subnanosecond range. Intense subnanosecond pulses have recently gained attention due to their potential ability to reach cells interior.

International audience; This technical note deals with a general class of discrete 2-D possibly nonlinear systems based on the Roesser model. We first motivate the introduction of Lyapunov type definitions of asymptotic and exponential stability. This will allow us to introduce and discuss several particularities that cannot be found in 1-D systems. Once this background has been carefully designed, we develop different Lyapunov theorems in order to check asymptotic and exponential stability of nonlinear 2-D systems. Finally we propose the first converse Lyapunov theorem in the case of exponential stability.

International audience; RF-MEMS technology permits practical implementations of high-Q (Q from 300 to over 1,000) tunable microwave filters with power handling in the >;1-10 W range, with significant tuning range (>;50% to 100%), and ultra-low power consumption. Continuously frequency-tunable filters with mechanical actuation in the opposite direction of RF-inducted pressure can reach powers up to several watts, using a variable compensation bias. Very high Q, and large tuning range can be achieved with this technology, both in planar and cavity tunable filters. Using several devices in parallel, RF-MEMS capacitor arrays can handle RF-powers better than 1 watt, without the need for any compensation tuning.

This paper presents a theoretical analysis of harmonically terminated high-efficiency power rectifiers and experimental validation on a class-C single Schottky-diode rectifier and a class- F-1 GaN transistor rectifier. The theory is based on a Fourier analysis of current and voltage waveforms, which arise across the rectifying element when different harmonic terminations are presented at its terminals. An analogy to harmonically terminated power amplifier (PA) theory is discussed. From the analysis, one can obtain an optimal value for the dc load given the RF circuit design. An upper limit on rectifier efficiency is derived for each case as a function of the device on-resistance. Measured results from fundamental frequency source-pull measurement of a Schottky diode rectifier with short-circuit terminations at the second and third harmonics are presented. A maximal device rectification efficiency of 72.8% at 2.45 GHz matches the theoretical prediction. A 2.14-GHz GaN HEMT rectifier is designed based on a class-F-1 PA. The gate of the transistor is terminated in an optimal impedance for self-synchronous rectification. Measurements of conversion efficiency and output dc voltage for varying gate RF impedance, dc load, and gate bias are shown with varying input RF power at the drain. The rectifier demonstrates an efficiency of 85% for a 10-W input RF power at the transistor drain with a dc voltage of 30 V across a 98-Ω resistor.

International audience; In this paper, a simple and accurate characterization method of the thermal impedance of silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) is proposed. This method relies on low-frequency S-parameter measurements in the 100 Hz-3 GHz frequency range. It is shown that feedback hybrid parameter h12 provides an image of the thermal impedance in the frequency domain, which is independent of the size of the transistor. Very short thermal time constants involved in SiGe HBTs are accurately determined by this method, as well as the temperature dependence of the thermal impedance in a truly simple way as electrical measurements can be performed in dc conditions either on a wafer or on an attached die. Finally, a nonlinear electrical equivalent circuit model is extracted, which can be readily implemented in computer-aided design software for nonlinear simulation of any SiGe HBT circuit.

International audience; A reconfigurable sub-reflectarray (RSRA) is studied to perform a realistic telecommunication scenario in Ku-band. The reflectarray panel is based on a proven technology with PIN diodes developed by Thales Airborne Systems and French Space Agency. This article presents different geometries of dual-reflector that can be used with this RSRA and the performances are compared, including quantization effects. It also presents that the main difficulty to tackle with RSRA is the alteration of the radiation patterns due to the specular radiation of the panel. Finally, two solutions to minimize this effect with RSRA are presented.

International audience; Salt-based aging plays an important part in the realism of scenes featuring stone structures and monuments. A proposed model, based on physical behaviors and principles, replaces the simulation of complex physical formulations with ad hoc algorithms. It leads to plausible results, ultimately helping designers create aging patterns on affected objects.

International audience; A reduced basis method is introduced to deal with a stochastic problem in a numerical dosimetry application in which the field solutions are computed using an iterative solver. More precisely, the computations already performed are used to build an initial guess for the iterative solver. It is shown that this approach significantly reduces the computational cost.

This letter presents the design of a low-profile, high-gain Yagi wire-patch antenna array that radiates a directional beam in the azimuthal plane within the frequency band 5.45-5.75 GHz. The elementary unit of a typical Yagi antenna is replaced by wire-patch antenna. This antenna delivers a gain of 14.8 dB at 5.6 GHz. A prototype of this modelized antenna is manufactured, and the measured performances are similar to the simulated ones.

International audience; Linear finite state machines (LFSMs) are particular primitives widely used in information theory, coding theory and cryptography. Among those linear automata, a particular case of study is linear feedback shift registers (LFSRs) used in many cryptographic applications such as design of stream ciphers or pseudo-random generation. LFSRs could be seen as particular LFSMs without inputs. In this paper, we first recall the description of LFSMs using traditional matrices representation. Then, we introduce a new matrices representation with polynomial fractional coefficients. This new representation leads to sparse representations and implementations. As direct applications, we focus our work on the Windmill generators case, used for example in the EO stream cipher and on other general applications that use this new representation. In a second part, a new design criterion called diffusion delay for LFSRs is introduced and well compared with existing related notions. This criterion represents the diffusion capacity of an LFSR. Thus, using the matrices representation, we present a new algorithm to randomly pick LFSRs with good properties (including the new one) and sparse descriptions dedicated to hardware and software designs. We present some examples of LFSRs generated using our algorithm to show the relevance of our approach.