Gaelle Lissorgues

Pebbles Tracking Thanks to RFID LF Multi-Loops Inductively Coupled Reader

The Radio Frequency IDentification (RFID) Low Frequency (LF) serial loops structure is proposed to improve TAGs detection when a TAG coil-antenna rotates by any angle, due to the tagged pebble moving. The detection zones of two types of TAGs (the token and glass TAG) and two types of reader coils, in function of the TAG size, TAG orientation and shape of the reader coils are tested. The effect of the proposed multi-coil inductively coupled is confirmed by measurement using a commercial LF RFID system.

Towards a frequency-selective microwave power limiter for defense and aerospace applications

An overview of high power microwave threats and the development of a distributed frequency-selective microwave power limiter are presented in this paper. The design of the proposed device is based on power dissipation by electron emission. Indeed vacuum components are supposedly able to handle very high frequency signals at high power levels. Electromagnetic simulations will be compared to broadband characterization results.

A hybrid finite-element method for the modeling of microcoils

This paper presents an original method for the modeling of microcoils at high frequency dedicated for different applications: radio frequency, nuclear magnetic resonance, nondestructive testing, etc. The aim of the modeling is to determine the elements of an electric equivalent circuit. A magneto-dynamic three-dimensional (3-D) finite-element formulation is used to calculate the resistance and the inductance of the microcoil at high frequency. Using the previous results, an electrostatic 3-D finite-element field analysis is then used to determine the capacitance. The method was tested by using an example of nuclear magnetic resonance microcoil. Numerical results obtained by the proposed method are compared with measurements and analytical results.

Improvement of HF RFID Tag Detection With a Distributed Diameter Reader Coil

This letter focuses on 13.56 MHz high-frequency radio frequency identification (RFID) in the case of small tags detection, with an effective area below 1 cm2. In such an identification system, based on load modulation principle, the magnetic coupling coefficient k and quality factor of the RFID reader coil are the key parameters. The main goal of this letter is to improve the detection of small tags over a given surface of 10 × 10 cm2 by modifying the reader coil structure, and consequently the coupling coefficient k. Several coil designs are compared experimentally by distributing the diameters of their turns among three possible values. The design of the coils is based on empirical formulas that are in good agreement with experimental measurements. Electromagnetic simulations are performed to confirm the magnetic field distribution of the different designs. The results show that distributed diameter coil (DDC) as RFID reader coil is clearly efficient in this context of the RFID detection. The DDC structures determine the k factor, and, as k is low, the quality factor Q is a second parameter that can improve, in a second step, the RFID detection performances in function of the tag position and orientation.

Detecting range and coupling coefficient tradeoff with a multiple loops reader antenna for small size RFID LF tags

This paper summarizes some tests with Low Frequency (LF, 125 kHz) RFID tags of two types: Card and Token. These tests were done in order to evaluate the feasibility of an identification/traceability of tags which size is constrained and supposed to be detected inside a delimited volume of 40×40×10 cm3. As the size of the antenna tag is supposed to be very small, we improve the detection range and volume of definition by designing different reader antennas. Reader antennas presented are of two types whether they are based on single (SL) or multiple loops (ML). Detection range was evaluated for planar antennas (3 SL and one ML). Volume of definition for the detection was estimated by designing two-level prototypes of ML antennas. Results are discussed about the optimization possibility of detection range and volume thanks to ML.

Interfacing neurons on carbon nanotubes covered with diamond

A recently discovered material, carbon nanotubes covered with diamond (DCNTs) was tested for its suitability in bioelectronics applications. Diamond shows advantages for bioelectronics applications (wide electro chemical window and bioinertness). This study investigates the effect of electrode surface shape (flat or three dimensional) on cell growth and behavior. For comparison, flat nanocrystalline diamond substrates were used. Primary embryonic neurons were grown on top of the structures and neither incorporated the structures nor did they grow in between the single structures. The interface was closely examined using focused ion beam (FIB) and scanning electron microscopy. Of special interest was the interface between cell and substrate. 5% to 25% of the cell membrane adhered to the substrate, which fits the theoretical estimated value. While investigating the conformity of the neurons, it could be observed that the cell membrane attaches to different heights of the tips of the 3D structure. However, the aspect ratio of the structures had no effect on the cell viability. These results let us assume that not more than 25% of cell attachment is needed for the survival of a functional neuronal cell.

Piezoelectric aluminum nitride resonator for oscillator

This work investigates properties of the thin film elongation acoustic resonator (TFEAR) operating at megahertz frequencies in air. This resonator is composed of a piezoelectric layer of AlN sandwiched between 2 Al electrodes. TFEAR works in the extensional mode excited via AlN d31 piezoelectric coefficient. A 3D finite element method (3D-FEM) analysis using ANSYS software has been performed to model static modal and harmonic behavior of the TFEAR. To consider insertion losses into the substrate, equivalent electrical models based on a modified Butterworth-Van Dyke (MBVD) circuit have been improved by adding extra dissipative elements. Thus, a whole model for the on-wafer characterization setup is given, allowing for automatic de-embedding of the present TFEAR equivalent circuit. Quality factors Q as high as 2500 in air have been recorded with motional resistance lower than 400 ¿. A first oscillator based on a TFEAR resonator was also designed and tested.

Towards a Fully Passive Ku-Band Power Limiter using RF-MEMS Technologies and Vacuum Microelectronics

The first steps leading to the development of an RF power limiter are presented in this paper. As vacuum components are supposedly able to handle very high frequency signals at high power levels, the proposed device is based on the use of cold cathode field emitters distributed along a coplanar line. Two and three-dimensional electromagnetic simulations will be compared to early characterization results at microwave frequencies and at medium power. First experiments at higher power will also be discussed

Monitoring the evolution of boron doped porous diamond electrode on flexible retinal implant by OCT and in vivo impedance spectroscopy.

Nanocrystalline Boron doped Diamond proved to be a very attractive material for neural interfacing, especially with the retina, where reduce glia growth is observed with respect to other materials, thus facilitating neuro-stimulation over long terms. In the present study, we integrated diamond microelectrodes on a polyimide substrate and investigated their performances for the development of neural prosthesis. A full description of the microfabrication of the implants is provided and their functionalities are assessed using cyclic voltammetry and electrochemical impedance spectroscopy. A porous structure of the electrode surface was thus revealed and showed promising properties for neural recording or stimulation. Using the flexible implant, we showed that is possible to follow in vivo the evolution of the electric contact between the diamond electrodes and the retina over 4months by using electrochemical impedance spectroscopy. The position of the implant was also monitored by optical coherence tomography to corroborate the information given by the impedance measurements. The results suggest that diamond microelectrodes are very good candidates for retinal prosthesis.

Modeling and fabrication of piezoelectric Aluminum Nitride resonator and its application in oscillators

This work investigates the TFEAR (Thin Film Elongation Acoustic Resonator) [1] operating at MHz frequencies. This resonator is composed of a piezoelectric Aluminum Nitride (AlN) layer sandwiched between two aluminum (Al) electrodes. The resonators are manufactured on a silicon substrate. In opposition to common resonator, TFEAR works in extensional (elongation) mode excited via AlN d31 piezoelectric coefficient. A Finite Element Analysis is performed to simulate the static and modal behaviors. The simulation is used to determine the geometry of each material so as to reach the desired frequency range and to compare theoretical and experimental results at different resonance frequencies. A modified Van-Dyke Butterworth (MBVD) equivalent circuit model is developed, including substrate losses. Samples have been measured and quality factor as high as 2500 in air have been measured. A first oscillator based on TFEAR resonator was designed and fabricated.