Multi-Level Pre-Correlation RFI Flagging for Real-Time Implementation on UniBoard

Because of the denser active use of the spectrum, and because of radio telescopes higher sensitivity, radio frequency interference (RFI) mitigation has become a sensitive topic for current and future radio telescope designs. Even if quite sophisticated approaches have been proposed in the recent years, the majority of RFI mitigation operational procedures are based on post-correlation corrupted data flagging. Moreover, given the huge amount of data delivered by current and next generation radio telescopes, all these RFI detection procedures have to be at least automatic and, if possible, real-time. In this paper, the implementation of a real-time pre-correlation RFI detection and flagging procedure into generic high-performance computing platforms based on Field Programmable Gate Arrays (FPGA) is described, simulated and tested. One of these boards, UniBoard, developed under a Joint Research Activity in the RadioNet FP7 European programme is based on eight FPGAs interconnected by a high speed transceiver mesh. It provides up to ~4 TMACs with Altera Stratix IV FPGA and 160 Gbps data rate for the input data stream. Considering the high in-out data rate in the pre-correlation stages, only real-time and go-through detectors (i.e. no iterative processing) can be implemented. In this paper, a real-time and adaptive detection scheme is described. An ongoing case study has been set up with the Electronic Multi-Beam Radio Astronomy Concept (EMBRACE) radio telescope facility at Nan\c{c}ay Observatory. The objective is to evaluate the performances of this concept in term of hardware complexity, detection efficiency and additional RFI metadata rate cost. The UniBoard implementation scheme is described.Comment: 16 pages, 13 figure

Redefining Performance Evaluation Tools for Real-Time QRS Complex Classification Systems

International audienceIn a heartbeat classification procedure, the detection of QRS complex waveforms is necessary. In many studies, this heartbeat extraction function is not considered: the inputs of the classifier are assumed to be correctly identified. This paper aims to redefine classical performance evaluation tools in entire QRS complex classification systems and to evaluate the effects induced by QRS detection errors on the performance of a heartbeat classification processing (normal vs abnormal). Performance statistics are given and discussed considering the MIT/BIH database records that are replayed on a real-time classification system imposed of the classical detector proposed by Hamilton & Tompkins, followed by a neural network classifier. This study shows that a classification accuracy of 96.72% falls to 94.90% when a drop of 1.78% error rate is introduced in the detector quality. This corresponds an increase of about 50% bad classifications

Détecteur robuste de signaux cyclostationnaires : application à la suppression d'interférences en radioastronomie

L'observation radioastronomique est de plus en plus fréquemment brouillée par les signaux de télécommunications numériques. Une solution consiste à détecter ces signaux et à suspendre les mesures. La nature cyclostationnaire des signaux enjeu peut être révélée par filtrage de Hilbert qui produit un signal périodique [2]. L'idée est ensuite d'utiliser la technique de Hinich de détection d'un signal périodique lorsque sa période est inconnue. Une étude expérimentale de la robustesse de ce détecteur de raies est présentée. L'application à la détection de signaux de type GLONASS donne des résultats encourageants

A Reversible Jump MCMC Algorithm for Particle Size Inversion in Multiangle Dynamic Light Scattering

Publication in the conference proceedings of EUSIPCO, Lisbon, Portugal, 201

Sparsity-Based Algorithms for Blind Separation of Convolutive Mixtures with Application to EMG Signals

International audienceIn this paper we propose two iterative algorithms for the blind separation of convolutive mixtures of sparse signals. The first one, called Iterative Sparse Blind Separation (ISBS), minimizes a sparsity cost function using an approximate Newton technique. The second algorithm, referred to as Givens-based Sparse Blind Separation (GSBS) computes the separation matrix as a product of a whitening matrix and a unitary matrix estimated, via a Jacobi-like process, as the product of Givens rotations which minimize the sparsity cost function. The two sparsity based algorithms show significantly improved performance with respect to the time coherence based SOBI algorithm as illustrated by the simulation results and comparative study provided at the end of the paper

Modélisation des disjoncteurs domestiques dans la bande CPL

Les études portant sur l'impact des éléments de protection du réseau électrique domestique sur les signaux CPL (courant porteur en ligne) manquent. Ce travail investigue l'effet des disjoncteurs domestiques dans la bande CPL. Avec un analyseur de réseau, les pertes d'insertion (paramètres S21) d'une dizaine de disjoncteurs de différents calibres et fabricants ont été mesurées. D'une part, l'atténuation des disjoncteurs dans la bande bas débit (9kHz-500 kHz) est faible. D'autre part, ils induisent une atténuation importante dans la bande haut débit (1MHz-100MHz). Ces pertes dépendent surtout du courant nominal et du type de disjoncteur (branchement, différentiel, divisionnaire). En tenant compte de leur structure, un circuit électrique équivalent des disjoncteurs est proposé et validé en comparant les simulations aux mesures. Ce circuit pourra être intégré dans un simulateur CPL

Analyse de l’activité à bord de dragues aspiratrices : une méthodologie exploratoire combinant données psychologiques et physiologiques

Cette étude a pour objectif d’explorer une méthodologie recoupant deux ordres de données, psychologiques et physiologiques, dans le cadre d’une analyse ergonomique de l’activité. Deux terrains d’étude, situations « naturelles », ont été investis : une drague aspiratrice stationnaire et une drague aspiratrice en marche, où nous nous sommes focalisés sur l’assistant de pont en charge de l’activité de dragage. Au niveau psychologique, notre méthode a consisté à croiser des observations ethnographiques avec des entretiens individuels compréhensifs. Au niveau physiologique, des mesures de la fréquence cardiaque (intervalle R-R) ont été réalisées à travers des enregistrements simultanés à l’activité.Nos résultats découlent alors de la confrontation de ces sources de données « objectives » et « subjectives ». Au poste du dragueur, la charge de travail paraît conséquente avec des actions courtes et nombreuses. Il semble nécessaire de maintenir un niveau de vigilance élevé, en fonction des différents paramètres à prendre en considération et des régulations multiples à fournir lors de la tâche. L’activité se complexifie selon la nature des fonds sous-marins, avec la survenue de nombreuses variations et l’apparition possible de stress lors de dragages sur fond chaotique. Cette prise en compte « intégrée » de l’activité humaine devrait permettre en retour l’amélioration de la sécurité des marins.The purpose of this study is to explore a methodology combining two types of data, psychological and physiological, through an ergonomic analysis of the activity. Two field studies were conducted: the stationary suction dredger situation, and the moving suction dredger situation, where we focused on the bridge assistant, responsible for the dredging activity. Two orders of data are considered: psychological and physiological. From a psychological point of view, our methodology cross-referenced ethnographic observations with non-directive interviews. At the physiological level, heart-rate measurements (R-R interval) were continuously recorded, throughout the activity. Our results proceed from the confrontation of these “objective” and “subjective” data sources. The workload at this work station appears to be considerable, with many short actions. It would seem necessary to maintain a high level of vigilance, due to the various parameters to be taken into account, and to the multiple adjustments which must be made during the task time. The activity can become more complex, depending on the nature of the seabeds: many variations can take place, and there may be occurrences of stress when dredging chaotic seabeds. This “integrated” approach to human activity should lead to improved safety for the sailors

After-Fatigue Condition: A Novel Analysis Based on Surface EMG Signals

This study introduces a novel muscle activation analysis based on surface electromyography (sEMG) signals to assess the muscle's after-fatigue condition. Previous studies have mainly focused on the before-fatigue and fatigue conditions. However, a comprehensive analysis of the after-fatigue condition has been overlooked. The proposed method analyzes muscle fatigue indicators at various maximal voluntary contraction (MVC) levels to compare the before-fatigue, fatigue, and after-fatigue conditions using amplitude-based, spectral-based, and muscle fiber conduction velocity (CV) parameters. In addition, the contraction time of each MVC level is also analyzed with the same indicators. The results show that in the after-fatigue condition, the muscle activation changes significantly in the ways such as higher CV, power spectral density shifting to the right, and longer contraction time until exhaustion compared to the before-fatigue and fatigue conditions. The results can provide a comprehensive and objective evaluation of muscle fatigue and recovery, which can be helpful in clinical diagnosis, rehabilitation, and sports performance

Optimized Method for Generating and Acquiring GPS Gold Codes

We propose a simpler and faster Gold codes generator, which can be efficiently initialized to any desired code, with a minimum delay. Its principle consists of generating only one sequence (code number 1) from which we can produce all the other different signal codes. This is realized by simply shifting this sequence by different delays that are judiciously determined by using the bicorrelation function characteristics. This is in contrast to the classical Linear Feedback Shift Register (LFSR) based Gold codes generator that requires, in addition to the shift process, a significant number of logic XOR gates and a phase selector to change the code. The presence of all these logic XOR gates in classical LFSR based Gold codes generator provokes the consumption of an additional time in the generation and acquisition processes. In addition to its simplicity and its rapidity, the proposed architecture, due to the total absence of XOR gates, has fewer resources than the conventional Gold generator and can thus be produced at lower cost. The Digital Signal Processing (DSP) implementations have shown that the proposed architecture presents a solution for acquiring Global Positioning System (GPS) satellites signals optimally and in a parallel way