G. Alquié - Academia.edu (original) (raw)

Papers by G. Alquié

Sensors, Cameras, and Systems for Industrial and Scientific Applications XIII, 2012

In order to build biological tissues spectral characteristics database to be used in a multispect... more In order to build biological tissues spectral characteristics database to be used in a multispectral imaging system a tissues optical characterization bench is developed and validated. Several biological tissue types have been characterized in vitro and ex vivo with our device such as beef, turkey and pork muscle and beef liver. Multispectral images obtained have been analyzed in order to study the dispersion of biological tissues spectral luminance factor. Tissue internal structure inhomogeneity was identified as a phenomenon contributing to the dispersion of spectral luminance factor. This dispersion of spectral luminance factor could be a characteristic of the tissue. A method based on envelope technique has been developed to identify and differentiate biological tissues in the same scene. This method applied to pork tissues containing muscle and fat gives detection rates of 59% for pork muscle and 14% for pork fat.

IRBM, 2018

h i g h l i g h t s g r a p h i c a l a b s t r a c t • A ring resonator for non-invasive microwa... more h i g h l i g h t s g r a p h i c a l a b s t r a c t • A ring resonator for non-invasive microwave dielectric characterization is proposed. • A CPW feeding structure is investigated to provide better coupling. • The distributed resonator has been miniaturized with a meander shape. • The sensor has a good accuracy even for high dielectric loss materials. • Dielectric parameters of several animal biological tissues have been extracted by ex-vivo measurements.

The physical model of the BDJ photo-detector is evaluated by comparing experimental results with ... more The physical model of the BDJ photo-detector is evaluated by comparing experimental results with simulations. The model is then improved using a parameter extraction method and by calculating the oxide layer effects. Finally the result model is implemented under SPICE simulators to provide electric simulation of the device.

An application of optically controlled gap integrated in an active MMIC is presented.The gap,inse... more An application of optically controlled gap integrated in an active MMIC is presented.The gap,inserted in a feedback amplifier,can optically modulate the active device.This topology could reduce the design complexity of digital wireless communication systems.

A state of the art of the modeling of microwave photoswitching devices is exposed. A new 3 D elec... more A state of the art of the modeling of microwave photoswitching devices is exposed. A new 3 D electromagnetic modeling allows the design of an optically-controlled microwave phase shifter microwave starting from the traditional circuit of a microwave photoswitch. Measurements of the parameters S of this optically-controlled microwave phase shifter attests the function of this circuit by optical way and highlights the interest of the integration of this new type of microwave phase shifters in systems of antennas arrays. A new optically-controlled microwave phase shifter with a patented structure is under development. I. OPTICALLY-CONTROLLED MICROWAVE SWITCHING

Microelectronics Journal

Abstract Microwave planar sensors have a great interest in the medical environment due to their a... more Abstract Microwave planar sensors have a great interest in the medical environment due to their ability to measure the bulk dielectric parameters of biological tissues through non-invasive and contact-less sensing properties. Changes of these parameters, which are frequency dependent, can be representative of the pathological state of biological tissues. In this work, an improved prototype of planar sensor based on a microwave ring resonator operating at 1 GHz for the fundamental mode is presented. The objective is to obtain a better sensitivity for measuring high complex permittivity values of materials such as biological tissues, and to obtain higher precision in parameters determination. The performances of two sensors optimized on two different substrates were measured in a frequency range 1–10 GHz; an accurate equivalent electrical model is proposed to reproduce the frequency dependence of the resonators. Characterization of liquids and ex-vivo animal tissues is achieved to evaluate the effectiveness and the performances of the resonator sensor, and results are compared with electromagnetic simulations.

Journal de Physique Lettres, 1983

2014 Des résultats nouveaux sur les deux phases cristallographiques du semiconducteur magnétique ... more 2014 Des résultats nouveaux sur les deux phases cristallographiques du semiconducteur magnétique GaCr4S8 sont présentés ; ils ont été obtenus par resonance de spins électroniques dans les états paramagnétique et magnétique ordonné de ces composés. Un comportement typique des transitions de phases magnétiques est observé; il est caractérisé par un déplacement et un élargissement du signal de résonance, ainsi que par une modification de sa forme. Ces effets sont interprétés en relation avec la présence de fluctuations d'aimantation. Abstract.-We present new results obtained from ESR experiments in the paramagnetic and magnetic ordered states of both crystallographic phases of the magnetic semiconductor GaCr4S8. We observe a critical behaviour typical of magnetic phase transitions, resulting in a shift and a broadening of the resonance line as well as a distortion of its shape. These features are discussed and related to the presence of magnetization fluctuations.

Journal de Physique Lettres, 1974

Journal De Physique Lettres, 1983

International Journal of Microwave and Wireless Technologies, 2009

The great interest of optical fiber links in communicating systems especially in ultra-wide band ... more The great interest of optical fiber links in communicating systems especially in ultra-wide band (UWB) communications has grown up in the last decade and requires co-simulation for mixed circuits design exploiting both optical and microwave domains. In this paper, we report an original modeling method of an electro-absorption modulator associated with a distributed-feedback laser to simulate an optical transmitter of an UWB over fiber system. Large signal optoelectronic device models can be developed and implemented in a high-frequency simulator, such as advanced design system-Ptolemy to analyze the performances of fiber radio links and study the impact of the transmitter characteristics. This specific simulation way, taking into account precisely electrical characteristics of both electrical and optical circuits, links two different frequency domains by coupling electrical and optical modules in the same system simulator. Therefore, a complete simulation of an UWB multi-band orthog...

2009 IEEE International Conference on Microwaves, Communications, Antennas and Electronics Systems, 2009

This paper presents an original 60 GHz architecture for Ultra-Wide Band (UWB) Radio-over-Fiber (R... more This paper presents an original 60 GHz architecture for Ultra-Wide Band (UWB) Radio-over-Fiber (RoF) systems to increase both the transmission distance and the high data bit rate. With a Central Station (CS) and a Base Station (BS), this architecture allows to send through an optical fiber both a subcarrier microwave signal and UWB baseband data by using a wavelength multiplexer. At the BS, the carrier frequency is photodetected, modulated by data and then up-converted to millimeter-wave band. Simulation results using VPIsystems software are reported and discussed for Multi-Band Orthogonal Frequency Division Multiplexing (MB-OFDM) signals.

Photonics North 2006, 2006

ABSTRACT Microwave photonics contributes through ultrafast devices to the processing of high data... more ABSTRACT Microwave photonics contributes through ultrafast devices to the processing of high data rates. In this area, microwave photoconductive switches (MPCSs) in integrated technology have proved their performances to control the transmission of high frequency signals in complex systems. Their ability to switch microwave signal phase and magnitude is fully defined by a complex frequency-dependant ON/OFF ratio RON/OFF determined from S-Parameters measurements in microwave frequency domain. This paper reports on a new design of MPCSs to be used, after realization and evaluation, as a basic block in optically controlled MMIC devices for application in high frequency samplers or phase shifters.

J3eA, 2005

-L'utilisation de l'effet photoconducteur pour contrôler des circuits intégrés microondes est ici... more -L'utilisation de l'effet photoconducteur pour contrôler des circuits intégrés microondes est ici exploitée. Le contrôle est effectué sur un composant passif : un gap microruban photocommutateur qui présente l'avantage de pouvoir être intégré aisément dans une technologie de circuits MMIC industrielle. Nous avons développé un modèle de photocommutateur nonlinéaire basé sur les mesures pour la conception d'un oscillateur MMIC à 5 GHz fabriqué selon la technologie UMS PH25 sur GaAs. Cet oscillateur délivre un signal lorsque le gap, placé sur la source du transistor, est éclairé (état ON) et ne fonctionne plus lorsque le gap n'est pas éclairé (état OFF). Ce fonctionnement repose sur la variation de l'impédance équivalente du gap en fonction de la puissance de l'éclairement. Les premiers tests de ce circuit opto-microonde sont présentés.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2006

Materials with atomic number Z as high as possible are considered for solid state X-ray imaging d... more Materials with atomic number Z as high as possible are considered for solid state X-ray imaging detectors in order to absorb the radiation efficiently. However, the energy and yield of the fluorescence photons increase also with Z, so that the contrast and spatial resolution of an image decreases with Z. We show that the Z value which optimizes the absorption and the image contrast for a given spatial resolution corresponds to GaAs. Now that the GaAs material (thick epitaxial layer) necessary to make pixel detectors exists, we illustrate the improvements in image quality this material brings by comparing, in case of imaging made with small pixels (100μm), the spatial resolution and contrast with that obtained using CdTe and CsI detectors. Using the Rose model which gives the signal-to-noise ratio corresponding to the minimum detectable contrast, we evaluate the minimum size of the object which can be detected in specific conditions with detectors made of GaAs, CdTe and CsI.