Performance Evaluation of 60-GHz-WPAN System Distributed Over Multi-Mode Fiber

The manuscript deals with the assessment of Radio over Fiber (RoF) system including pure electrical baseband, pure radio frequency band centered around 60 GHz, and hybrid radiooptical system at the same RF band using a global simulation.In this work we focus on RoF solution to improve the low coverage of the 60 GHz channel caused by high free-space attenuation. A realistic co-simulation of the Wireless PersonalArea Network (WPAN) IEEE802.15.3c-RoF was performed in aresidential environment for Line-Of-Sight (LOS) and Non-Line-Of-Sight (NLOS). In this work, we demonstrated a 60 GHz radio on Multi-Mode Fiber (MMF) using Optical Carrier Suppression (OCS) modulation. The BER (Bit Error Ratio) performance of this system is measured by varying the following parameters: optical launched power, fiber length, modulation format, Channel coding and Signal to Noise Ratio. We show that the RoF at 60 GHz can reach a minimum of 300 m of MMF without optical amplifiers followed by a 5 m wireless transmission with BER less than 10-3 in the LOS and NLOS environments

RF wafer probing with improved contact repeatability using nanometer positioning

International audienceThis paper presents an improved technique for monitoring and controlling the contact condition of on-wafer RF probes with nanometer accuracy to enhance the measurement repeatability. The set-up consists of a vector network analyzer, a modified probe station with a planar calibration substrate aligned under microwave GSG probe through a closed-loop nanopositioner and a camera system. A fully one-port SOL calibration is performed in the frequency range 0.05-50 GHz. A repeatability study based on standard deviations of the measured data considering both conventional and proposed approaches is described. From these experimental results, the improvement of the technique proposed is achieved by accurately controlling the probe contacts

Twinning for graphene-based composites in EMI shielding

In the era of intensive development of microelectronics, energy, and car industries along with Radio-Frequency (RF) telecommunications, the pollution caused by Electromagnetic Waves (EWs) is ever-present. EW interferences (Electromagnetic Interference-EMI) exhibit perturbation and negative impact on devices and systems including those used in everyday life as well as on the specialized, sensitive, and sophisticated instruments used in research laboratories. EMI could cause untrusted signals and RF noise. To prevent these issues, materials able to block or absorb the radiated EWs are urgently required. The GrInShield project is focused on developing new graphene-based shielding nano-materials and increasing researchers' expertise in EMI shielding measuring, protective materials, and possibilities to bring these new products to the market. INTRODUCTION: The GrInShield project uses graphene oxide (GO) obtained by Hummers' reaction and electrochemical exfoliation of graphite [1,2]. We have analysed the factors that affect the shielding efficiency of materials [3] and studied the reaction conditions that lead to obtaining graphene with different sizes and oxygen content [4]. RESULTS AND DISCUSSION: The GrInShield project aims to produce composites of GO with silver nanowires (AgNWs) to develop GO-AgNW composites for EMI shielding applications. To achieve these goals, the project gathers experts from the chemistry of nanomaterials, and polymer processing, along with specialists for near-field microscopy tools and radiofrequency (RF) characterization of materials. CONCLUSIONS: The GrInShield project is developing new nanomaterials for EMI shielding based on carbon nanomaterials, metallic nanomaterials, and polymers. The fabrication of low-cost, sustainable, eco-friendly, durable EMI shielding material should be achieved.Supplementary Issue - ExcellMater Conference 2024Innovative biomaterials for novel medical devices conference : AbstractsAvailable on-line at the Journal web address: [https://www.ache.org.rs/HI/

Graphene oxide-silver nanowires composites for protection against modern pollution - electromagnetic waves

With the development of the electronic industry, telecommunication, transportation, energy storage devices, and wireless technologies, the need for materials that are able to block electromagnetic waves (EMWs) in low-frequency regions of the spectrum is increasing. A new type of pollution named pollution by EMWs is an inevitable component of modern life. Although materials efficient in blocking the propagation of EMWs are developed, these materials show drawbacks regarding durability and mechanical properties, as well as a high production price and processability. Thus, new eco-friendly and durable materials are needed. Herein, we produced composites based on graphene oxide and silver nanowires to create an efficient shielding barrier for low frequencies (0-15 GHz) EMWs

Scanning Microwave Microscopy of Vital Mitochondria in Respiration Buffer

We demonstrate imaging using scanning microwave microscopy (SMM) of vital mitochondria in respiration buffer. The mitochondria are isolated from cultured HeLa cells and tethered to a solid graphene support. The mitochondria are kept vital (alive) using a respiration buffer, which provides nutrients to sustain the Krebs cycle. We verify that the mitochondria are "alive" by measuring the membrane potential using a voltage sensitive fluorescent dye (TMRE). The organelles are measured capacitively at 7 GHz. Several technical advances are demonstrated which enable this work: 1) The SMM operates in an electrophysiologically relevant liquid (hence conducting) environment; 2) The SMM operates in tapping mode, averaging the microwave reflection measurement over many tapping periods; 3) A tuned reflectometer enables increased sensitivity; 4) Variable frequencies up to 18 GHz are used; 5) In contrast with traditional matching/resonant methods that exhibit high quality factor that fail in the presence of liquids, interferometric/tuned reflectometer gives the possibility to adjust the quality factor or sensitivity even in the presence of the liquid.Comment: Accepted for publication in IMS 201

Measurement of EMI shielding perfomance of graphene oxide – silver nanoparticles composites

Silver nitrate has been exposed to low-dose (1–20 kGy) gamma irradiation in the presence of graphene-based material (graphene oxide or electrochemically exfoliated graphene) to form silver nanoparticles (Ag NPs). The successful nucleation and growth of Ag NPs, which produce the evenly covered graphene surface, are made possible by the vast surface area of those graphene-based materials as well as the presence of oxygen-containing functional groups on the surface. With a significant size distribution of 10–50 nm for graphene oxide and 10–100 nm for electrochemically exfoliated graphene, the produced Ag NPs were spherical. We also performed ElectroMagnetic Interference (EMI) shielding performance measurements of these materials. EMI shielding performance measurement revealed relatively good performance of the EEG material whereas GO material does not show EM shielding.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

Measurement of EMI shielding performance of graphene oxide and electrochemically exfoliated graphene thin films

Graphene and its derivatives have become the scientific community's focus due to their remarkable electronic, mechanical, and optical properties. In this work, we prepared two graphene-based materials, graphene oxide (GO) and electrochemically exfoliated graphene (EEG), and performed morphological and structural analysis. Both materials showed good dispersibility in water. GO is composed of mainly single- and few-layer graphene sheets, while EEG is predominately multi-layer graphene. EEG showed better thermal stability under nitrogen flow compared to GO. We also performed ElectroMagnetic Interference (EMI) shielding performance measurements of these materials

A review on graphene and graphene composites for application in electromagnetic shielding

As wireless solutions for communication, information, and sensing in modern society, electromagnetic waves (EMWs) have contributed considerably to the increase in the quality of people’s everyday lives. At the same time, EMWs produce electromagnetic pollution, issues with electromagnetic interference (EMI), and radio frequency (RF) signal leakage. These circumstances lead to high demand for efficient EMI shielding materials. To design an EMI shielding product, a compromise must be achieved between the electromagnetic shielding efficiency, the thickness of shielding materials, durability, mechanical strength, reduced volume and weight, and elasticity. Due to its ability to block EMWs, flexibility, lightweight, and chemical resistivity, graphene has been identified as a promising candidate material for efficient EMI shielding. Herein, we reviewed the studies that investigated various graphene-based composites as potential EMI shielding materials, with a focus on the composites based on graphene and silver nanowires due to their high EMI shielding efficiency, low production price, and favorable mechanical properties

Reordering Columns for Smaller Indexes

Column-oriented indexes-such as projection or bitmap indexes-are compressed by run-length encoding to reduce storage and increase speed. Sorting the tables improves compression. On realistic data sets, permuting the columns in the right order before sorting can reduce the number of runs by a factor of two or more. Unfortunately, determining the best column order is NP-hard. For many cases, we prove that the number of runs in table columns is minimized if we sort columns by increasing cardinality. Experimentally, sorting based on Hilbert space-filling curves is poor at minimizing the number of runs.Comment: to appear in Information Science

Approches informationnelles pour la fusion tolérante aux fautes – Application à la robotique mobile

International audienc