Christian Vollaire

Speech auditory brainstem response (speech ABR) characteristics depending on recording conditions, and hearing status An experimental parametric study.

Speech elicited auditory brainstem responses (Speech ABR) have been shown to be an objective measurement of speech processing in the brainstem. Given the simultaneous stimulation and recording, and the similarities between the recording and the speech stimulus envelope, there is a great risk of artefactual recordings. This study sought to systematically investigate the source of artefactual contamination in Speech ABR response. In a first part, we measured the sound level thresholds over which artefactual responses were obtained, for different types of transducers and experimental setup parameters. A watermelon model was used to model the human head susceptibility to electromagnetic artefact. It was found that impedances between the electrodes had a great effect on electromagnetic susceptibility and that the most prominent artefact is due to the transducers electromagnetic leakage. The only artefact-free condition was obtained with insert-earphones shielded in a Faraday cage linked to common ground. In a second part of the study, using the previously defined artefact-free condition, we recorded speech ABR in unilateral deaf subjects and bilateral normal hearing subjects. In an additional control condition, Speech ABR was recorded with the insert-earphones used to deliver the stimulation, unplugged from the ears, so that the subjects did not perceive the stimulus. No responses were obtained from the deaf ear of unilaterally hearing impaired subjects, nor in the insert-out-of-the-ear condition in all the subjects, showing that Speech ABR reflects the functioning of the auditory pathways.

Efficient design of rectifying antennas for low power detection

This article is dedicated to the design of rectifying antenna for wireless energy transfer at 2.45 GHz in the special case of low input power (typically <−10 dBm). As the rectifiers present an important non-linear behavior with such power levels, specific design guidelines must be respected in order to optimize the structure. Different rectifying circuits have been studied and their performances have been evaluated through the definition of a Figure of Merit. The effects of the antenna impedance have also been investigated to improve the performances. Two test-circuits have been manufactured and measured to validate the simulation results and to confirm the interest of a global design approach with such rectifying structures.

Conducted EMI prediction for integrated class D audio amplifier

The aim of this paper is to predict the delivered currents at the output of an integrated audio switching amplifier for EMI prediction. Impedance matrices are used to model the different passive parts of the system. Hereafter, all the matrices are associated in a single one, where the resulting matrix and the output voltages in open circuit are used to predict the output currents spectra directly in the frequency domain. This method can be used by system designers and system integrators in order to study their systems EM emissions before assembling the different parts of the system. The experimental application of this method gives good accuracy up to 10 MHz (twenty times the switching frequency).

Conducted EMC prediction for a power converter with SiC components

This paper presents a model of a power converter with SiC components in order to predict the conducted perturbation that it generates (at the LISN level). Some methods to create a model of any passive elements (parasitic capacitance and inductance, decoupling capacitors, load, LISN) as an equivalent circuit are shown. Finally the complete model of the converter is presented and confronted to experimental measurements. Comparisons show a good behaviour until 30MHz.

Systematic LFT Derivation of Uncertain Electrical Circuits for the Worst-Case Tolerance Analysis

In line with the trend toward continuous miniaturization and price reduction, it is crucial to analyze the impact of uncertainties on the performance of electrical circuits. Performance is evaluated for the worst-case scenario and in the frequency domain by computing upper and lower bounds. The purpose is not only to propose a method for the worst-case tolerance analysis but also to provide an efficient and a suitable tool for electrical engineers that can be easily applied to realistic electrical engineering problems. The proposed method is based on the robust analysis method (so-called μ-analysis) for which well known and efficient algorithms exist. However in order to apply it, the problem under consideration has to be transformed in a standard minimal so-called LFT representation. Its derivation is a difficult task even for control systems engineers. This paper proposes a transparent and systematic LFT derivation procedure for users based only on their knowledge of electrical engineering. At the end of this paper, an industrial example is provided, which reveals the benefits and the efficiency of the proposed approach, and how it can be applied to any linear electrical circuit.

Adaptive unscented transform for uncertainty quantification in EMC large-scale systems

The Unscented Transform (UT) is a stochastic collocation method used for uncertainty quantification in nonlinear systems. This methodology is particularly interesting for EMC models with high-fidelity simulations which are time-consuming, since it demands only a few runs of the electromagnetic solver. However, since the number of simulations required by the UT increases exponentially with the number of dimensions, this methodology becomes unpractical for large-scale systems. Nevertheless, an adaptive Unscented Transform can be an efficient alternative of uncertainty propagation for these large dimensional systems.

Wireless Energy Transfer Using Zero Bias Schottky Diodes Rectenna Structures

This paper presents several RF-to-DC converter topologies and compares their performances based on measurements made on fabricated prototypes. A medium range wireless low power transmission experiment is presented. A low power DC-DC boost converter designed rectenna-generated energy conditioning is also discussed.

Autonomous Flyback Converter for Energy Harvesting from Microbial Fuel Cells

Cover letter An autonomous flyback converter was designed for energy harvesting from Microbial Fuel Cells (MFCs). The circuit was optimized to minimize the losses and maximize the efficiency. A Maximum Power Point Tracking (MPPT) algorithm was implanted in the converter to extract the maximum power available from MFC. Discontinuous conduction mode operation of the flyback allows controlling the MPP operation by impedance matching. The flyback can start-up at low voltage, around 300 mV. The output open circuit voltage is about 20 V and the voltage at MPP is 6.4 V with a maximum efficiency of 71.2%. Abstract: Microbial fuel cells (MFCs) use bacteria as the catalysts to oxidize organic matter and generate electricity. This energy can be used to supply low power electronic systems. A power management unit between the MFCs and the load is required to adapt the voltage and control the operation. The low voltage and low power characteristics of MFCs prohibit the use of standard converter topologies since the threshold voltage of standard CMOS transistors in CMOS technology is higher than the output voltage of MFCs. A low-voltage start-up sub-circuit is required to charge a primary capacitor to supply the driver. A specific sub-circuit is also required to control the operation of MFCs for Maximum Power Point Tracking (MPPT) issues. An optimized Discontinuous Conduction Mode (DCM) autonomous flyback converter for energy harvesting is presented for ambient sources, like MFCs. The converter is designed, fabricated, and tested. An MPPT algorithm is integrated in the system to control the operation and to extract the maximum available power from the MFC. The converter is able of start and step-up MFC output voltage to a value higher than 3 V under load. The peak efficiency of the converter is 71.2%.

Integrated Class-D audio amplifier virtual test for output EMI filter performance

This paper proposes a model based on the segmentation technique that can be used for electromagnetic interference (EMI) filter test by simulation. It is dedicated for systems with a differential output. The present approach proposes virtual measurement of the filter performance in the final application. Thus, the source emissions and the load impedance are taken into account. The proposed approach uses impedance matrices to model the passive parts of the system. A matrix calculation permits to associate these matrices and create a compact model. The impedance matrices and the converter output voltages are used for currents and voltages computation at all the system points. Finally, the proposed method is applied and validated on a Class-D amplification system. This method shows good accuracy on the [1kHz-120MHz] frequency band.

Conducted interferences of power converters with parametric uncertainties in the frequency domain

This paper presents a new methodology to analyse the conducted interferences of power converters when its parameters are described by probability density functions rather than numerical values. The methodology has several advantages when compared to classical approaches, such as Monte Carlo and Collocation methods. The results are presented as probability density functions and confidence intervals.