Filter optimization for real time digital processing of radiofrequency signals: application to oscillator metrology

International audienceSoftware Defined Radio (SDR) provides stability, flexibility and reconfigurability to radiofrequency signal processing. Applied to oscillator characterization in the context of ultrastable clocks, stringent filtering requirements are defined by spurious signal or noise rejection needs. Since real time radiofrequency processing must be performed in a Field Programmable Array to meet timing constraints, we investigate optimization strategies to design filters meeting rejection characteristics while limiting the hardware resources required and keeping timing constraints within the targeted measurement bandwidths

FPGA Implementation Of Diffusive Realization For A Distributed Control Operator

International audienceWe focus on the question of real-time computation for optimal distributed filtering or control applicable to MEMS Arrays. We present an algorithm for the realization of a linear operator solution to a functional equation through its application to a Lyapunov operatorial equation associated to the heat equation in one dimension. It is based on the diffusive realization, and turns to be well suited for fined grained parallel computer architecture as Field Programmable Gate Arrays (FPGA). An effective FPGA implementation has been successfully carried out. Here, we report the main implementation steps and the final measured performances

A cost effective AFM setup, combining interferometry and FPGA

International audienceAtomic force microscopes (AFM) provide high resolution images of surfaces. In this paper, we focus on an interferometry method for estimation of deflections in arrays of cantilever in quasi-static regime. We propose a novel complete solution with a least square based algorithm to determine interference fringe phases and its optimized FPGA implementation. Simulations and real tests show very good results and open perspectives for real-time estimation and control of cantilever arrays in the dynamic regime

Fast contactless vibrating structure characterization using real time field programmable gate array-based digital signal processing: Demonstrations with a passive wireless acoustic delay line probe and vision

International audienceVibrating mechanical structure characterization is demonstrated using contactless techniques best suited for mobile and rotating equipments. Fast measurement rates are achieved using Field Programmable Gate Array (FPGA) devices as real-time digital signal processors. Two kinds of algorithms are implemented on FPGA and experimentally validated in the case of the vibrating tuning fork. A first application concerns in-plane displacement detection by vision with sampling rates above 10 kHz, thus reaching frequency ranges above the audio range. A second demonstration concerns pulsed-RADAR cooperative target phase detection and is applied to radiofrequency acoustic transducers used as passive wireless strain gauges. In this case, the 250 ksamples/s refresh rate achieved is only limited by the acoustic sensor design but not by the detection bandwidth. These realizations illustrate the efficiency, interest, and potentialities of FPGA-based real-time digital signal processing for the contactless interrogation of passive embedded probes with high refresh rates

Un oscilloscope pour le traitement de signaux radiofréquences : gr-oscilloscope pour GNU Radio 3.7 et 3.8

International audienceGNU Radio, environnement libre de traitement de signaux radiofréquences, encourage le développement de blocs de traitements dédiés (Out Of Tree modules – OOT). Alors qu’une multitude d’interfaces matérielles dédiées sont supportées par GNU Radio [1], elles ont toutes en commun de fournir un flux de données continu de bande passante limitée par les débits de communication vers l’unité de traitement – Ethernet ou USB le plus souvent. Lors de traitements RADAR de distance de cibles, deux conditions sont respectées par les oscilloscopes radiofréquences : le flux de données n’a pas besoin d’être continu, nous n’avons besoin que de traiter une profondeur mémoire déterminée par la plus grande distance (temps de vol)de la cible à détecter ; et plus la bande passante est grande, meilleure est la résolution. Une bande passante B d’un GHz permet d’espérer une résolution en distance∆R=c/(2B) de l’ordre de 15 cm, objectif typique pour des mesures de glissement de terrain par exemple. Or aucune interface de radio logicielle accessible au grand public ne fournit une telle bande passante – alors que “n’importe quel” oscilloscope radiofréquence fournit actuellement allègrement quelques Géchantillons/s.De plus, nombre d’oscilloscopes fournissent 4 voies, permettant donc 4 flux d’acquisition, propices aux mesures de direction d’arrivée des signaux

Passive Radar Delay and Angle of Arrival Measurements of Multiple Acoustic Delay Lines Used as Passive Sensors

International audienceAfter introducing noise radar probing of acoustic delay lines used as passive tags and sensors, we demonstrate the use of non-cooperative radiofrequency signal sources for such purposes in the context of passive radar measurement. A practical demonstration using IEEE 802.11n (WiFi) is given for a sensor operating at 2.42 GHz, solving the regulatory certification issue met when deploying dedicated radiofrequency emitters for short range radar applications. Furthermore, synthetic aperture radar measurement is completed by replacing the single surveillance antenna with a linear uniform array, solving the sensor collision issue when multiple targets are within range of the radar system

Utilisation de la radio logicielle pour la caractérisation d’oscillateurs ultra-stables

International audience<font face="null"&gt<span style="font-size: 13px;"&gtUtilisation de la radio logicielle pour la caractérisation d’oscillateurs&nbsp; ultra-stables</span&gt</font&g

Noise in high-speed digital-to-analog converters

International audienceWe report on the measurement of phase noise of high speed analog to digital converters in a full digital measurement setup and for various development boards. The tested configurations ensures a Nyquist rate higher than 100 MHz suitable for conventional ultralow noise devices. Several analog to digital converters featuring a SNR higher than 140 dB enable the measurement of AM and PM noise with a background noise of -185 dBc (floor) and -160 dBc (flicker, 10 Hz off the carrier) using cross-correlation technique

Real time GNSS spoofing detection and cancellation on embedded systems using Software Defined Radio

International audienceGlobal Navigation Satellite Systems have become ubiquitous to most daily activities requiring Positioning, Navigation and Timing and yet have become increasingly subject to spoofing and jamming, partly due to the availability of affordable software defined radio platforms allowing such functionalities.<br&gtDespite novel modulation schemes and broader frequency bands, GPS L1 at 1575.42 MHz remains the main signal source for most consumer grade receivers. We address here real time spoofing and jamming mitigation using a software defined radio approach in which the raw (I, Q) coefficients collected by the radiofrequency frontend are analyzed for spoofing detection by assessing the phase difference of the GPS signals collected by different antennas. These signals are possibly cleaned from the interfering sources by null-steering when spoofing or jamming is detected, and the cleaned signal are used for real time Position and Navigation information extraction using the opensource<br&gtgnss-sdr framework. The application to other frequency bands is considered for redundancy and detecting spoofing attacks.<br&gtTiming information is under consideration as well

Software-Defined Radio Implemented GPS Spoofing and Its Computationally Efficient Detection and Suppression

International audienceThis article demonstrates global positioning system (GPS) spoofing with a commercial, off-the-shelf software-defined radio (SDR) emitter fitted with a local oscillator exhibiting a stability consistent with the medium-term (0.01-1 000 s) stability of atomic clocks on GPS satellite systems. Computationally efficient means of detecting spoofing is then addressed, namely codeless spoofing detection by phase-difference measurement of the signals received from a two-antenna array. We conclude by using a simple and effective method to suppress spoofing to restore positioning and time-transfer capabilities, and extend the demonstration to jamming cancellation. Experiment results demonstrate the performance of the proposed methods with an emphasis on computational efficiency for real-time execution on embedded single-board computers