Georges Alquié

Investigation of a buried double p-n junction structure implemented in CMOS technology for wavelength-sensitive detection

A buried double p–n junction (BDJ) structure in a CMOS process has been investigated to validate a wavelength-sensing method, which consists in using the ratio of the deep junction current to the shallow junction current for wavelength determination. Theoretically, an analytical BDJ device model has been established; and experimentally a chip incorporating BDJ sensing elements as well as electronic circuitry has been designed and measured. Both simulated and measured results, which are in good agreement, confirm the monotonic increase of the spectral response of the ratio. This allows the dominant wavelength of the incident light to be identified.

Theoretical and Experimental Evaluation of Superstrate Effect on Rectangular Patch Resonator Parameters

In this paper, modeling and experimentation of a Rectangular Patch Resonator (RPR) covered with a dielectric superstrate are investigated. The RPR criteria are established theoretically and experimentally, to be used in future prospects as an electromagnetic (EM) sensor for the characterization of superstrates. The theoretical model is based on the moment method (MoM) via Galerkins approach, in which three types of basis and testing functions are used. These functions as well as the spectral dyadic Green function are efficiently implanted with compact structured Fortran 90 codes. The EM commercial HFSS and CST Microwave Studio softwares are used to simulate the proposed RPR prototypes. The accuracy of the obtained results is assessed using four prototypes of RPRs operating around 6 GHz, taking into account only the resonant frequency of the fundamental dominant mode. The theoretical model is compared to simulation and measurement results, and very good agreements are observed.

Optical Transimpedance Receiver for High Data Transmission in OFDM Modulation Format

This paper presents the design and performance of a single-ended transimpedance amplifier (TIA) for gigabit passive optical networks implementing orthogonal frequency division multiplexing modulation format. The circuit is realized using an industrial GaAs integrated technology. Low power consumption and small chip area are the main challenges in the TIA design. On-wafer characterization in terms of S-parameters, noise figure, gain compression, and intermodulation are presented and compared to simulated results showing a good agreement. The TIA is linked with a broadband PIN photodiode and introduced in a radio over fiber system. The optical link is simulated in a microwave software and characterized in terms of error vector magnitude by varying the radio frequency input power and the laser bias current.

Rectangular patch resonator sensors for characterization of biological materials

The concept of using rectangular patch resonator (RPR) sensors for microwave characterization of biological materials is the non-invasive nature of the technique. It is being used extensively for the complex dielectric properties measurements of materials in the microwave region. Applications in microwave systems, the dielectric substrate and superstrate are made with low loss materials for the best operation. When RPR is used as the sensor, the superstrate is made with the unknown material under test; the objective is then to extract from measurements the dielectric parameters of this material. An accurate modeling of structures, associated with measurement data, is required to obtain, right values of dielectric parameters of unknown material by solving the inverse problem. Our research was established on the implementation of RPR prototypes, in order to be used as a biosensor for non-invasive testing and medical applications to characterize the dielectric properties of various biological materials. Our measurements showed that the complex dielectric properties obtained by this technique are in good agreement with simulations using C.Gabriel & al comparative data.

A 40 Gbps electro-absorption modulator integrated laser modeling method for optical transmitter in ultra-wide band radio-over-fiber systems

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 orthogonal frequency division multiplexing signal transmission over fiber with an external modulator is investigated.

Optoelectronic library for color sensor design

An optoelectronic PDK library including Buried Double pn Junction (BDJ) detector and optical stimuli is implemented for Spectre simulator by writing the behavioral models in Verilog-A, analog subset of Verilog-AMS language. In order to ensure accurate behavioral description of the BDJ detector, an improved physical model is proposed. To validate the accuracy of the model, measurements of dark and photogenerate currents are curried out on a CMOS test circuit and compared to simulation results. Under Cadence Virtuoso Custom Design Platform, the BDJ device can be connected to its readout circuits and to an optical stimulus in order to perform optoelectronic simulations. This affords a reliable solution for color sensor design.

A 60 GHz Radio-over-Fiber architecture for the transmission of UWB-OFDM signals

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.

Contribution to quality assessment of digital halftoning algorithms

Many new proposals are continually published in the halftoning domain. Alas, the demonstration of the interest of the proposed methods is often limited to a few favourable tests for the proposed methods, and images showing the defects of the other halftoning methods. The halftoning community needs to be able to compare a halftoning method with the innovations that appear in this domain. A complete and measured evaluation of quality is necessary through to a well defined set of test images and metrics to evaluate the algorithm. This paper proposes a protocol for the quality assessment of digital halftoning algorithm that can be used to compare one algorithm to another. It discusses the assessment of halftoner quality. It analyzes the perceived image quality concepts and defines the technical criteria that a good halftoner must match. A first sketch of a simple quality assessment protocol is proposed. It is composed of test images and quality metrics. This protocol could be used to provide new proposed halftoning algorithms with objective results.

Modeling and simulation under SPICE of optoelectronic systems including BDJ detector

We have recently developed in our laboratory a new integrated photodetector called BDJ. This detector allows determination of the wavelength of a monochromatic light. It was used to realize colorimetric applications. To develop such optoelectronic systems or microsystems we need simulations of their electronic behavior. Simulators like SPICE give in their libraries models for electrical components but not for optoelectronic components like photosensors or optic system. So we have developed a SPICE model to simulate the BDJ detector behavior and the optic source response. This model was implemented under SPICE and to illustrate its use, we have chosen to simulate two colorimetric applications developed in our laboratory; the first one allows determination of iron concentration and the second of the pH of solutions. In these applications, the optic system is composed of a light source (in practice Leds), and of a tube containing a liquid sensitive to the incident light wavelength; the transmission coefficient of the liquid depends on iron concentration in the first case and on reactive concentration and pH in the second case. Behavioral models of this optic system were included in the BDJ detector SPICE model. So we can obtain photocurrents ratio versus iron concentration or pH and reactive concentration. This system was simulated with an electronic associated circuit. This circuit is a classic analog circuit including several operational amplifiers. The optoelectronic system with associated circuit was described and simulated under SPICE and gives good results in comparison with measurements.

Biosensor miniaturization for non-invasive measurements of materials and biological tissues

This paper presents about non-invasive planar complementary split ring resonators (CSRRs) coupled to microstrip line to measure the dielectric properties of materials and biological tissues. The expectations of health professionals are increasingly turning to less invasive surgical procedures and treatments. In particular, the monitoring of vital parameters (sweat, water in the lungs, etc.) or the evolution of certain pathologies, such as cancer cells, could be observed regularly if suitable devices were developed and could especially replace traditional invasive method. Appropriate miniaturized RF or microwave devices could be an alternative for some medical diagnostic applications. These devices would make it possible to determine the dielectric characteristics of biological tissues, which represent their real pathological states. Thus, it would be possible that dielectric contrast measurements will be able to follow the evolution of pathology, as well as the vital parameters of a patient. The objective of this research is to investigate a prototype biosensor that is suitable for measurements on biological tissues and can be miniaturized to enhance its spatial sensitivity. This work focuses on the design, electromagnetic simulations, and characterization of a new miniaturized biosensor at 2.4 GHz. The ex-vivo experimental results will be shown by measuring the S-parameters of various materials and animal biological tissues. The extraction of the dielectric parameters of these samples is obtained by the measurements of materials.