13 research outputs found
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 radiofrĂ©quences, encourage le dĂ©veloppement de blocs de traitements dĂ©diĂ©s (Out Of Tree modules â OOT). Alors quâune multitude dâinterfaces matĂ©rielles dĂ©diĂ©es sont supportĂ©es par GNU Radio [1], elles ont toutes en commun de fournir un flux de donnĂ©es continu de bande passante limitĂ©e par les dĂ©bits de communication vers lâunitĂ© de traitement â Ethernet ou USB le plus souvent. Lors de traitements RADAR de distance de cibles, deux conditions sont respectĂ©es par les oscilloscopes radiofrĂ©quences : le flux de donnĂ©es nâa pas besoin dâĂȘtre continu, nous nâavons besoin que de traiter une profondeur mĂ©moire dĂ©terminĂ©e par la plus grande distance (temps de vol)de la cible Ă dĂ©tecter ; et plus la bande passante est grande, meilleure est la rĂ©solution. Une bande passante B dâun GHz permet dâespĂ©rer une rĂ©solution en distanceâR=c/(2B) de lâordre 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 â alors que ânâimporte quelâ oscilloscope radiofrĂ©quence fournit actuellement allĂšgrement quelques GĂ©chantillons/s.De plus, nombre dâoscilloscopes fournissent 4 voies, permettant donc 4 flux dâacquisition, propices aux mesures de direction dâarrivĂ©e des signaux
Utilisation de la radio logicielle pour la caractĂ©risation dâoscillateurs ultra-stables
International audience<font face="null"><span style="font-size: 13px;">Utilisation de la radio logicielle pour la caractĂ©risation dâoscillateurs ultra-stables</span></font&g
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>Despite 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>gnss-sdr framework. The application to other frequency bands is considered for redundancy and detecting spoofing attacks.<br>Timing 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
Implementation of a tunable hybrid system with coupled high Q-factor resonators based on mode localization for sensing purposes
International audienceIn this paper, we present a fully tunable system able to generate mode localization between a 170 000 Q-factor quartz crystal microbalance at 1 MHz and a digital device (field programmable gate array) simulating in real time the presence of an identical and weakly-coupled second resonator. Indeed, this method allows to precisely select each parameter value and thus to reach the optimal configuration with the maximum sensitivity to perturbations. In addition, this design gives a perfect adaptability to the geometry of the piezoelectric resonator, that allows to work with much higher frequencies and Q-factors than conventional cantilevers or tuning-forks usually selected for the design of mode-localized sensors. The experimental sensitivities reached in this work are at least two orders of magnitude higher than the ones found in the literature, which is promising for the design of a new generation of ultrasensitive sensors based on Anderson localization
Filter Optimization for Real-Time Digital Processing of Radio Frequency Signals: Application to Oscillator Metrology
International audienceSoftware-defined radio (SDR) provides stability, flexibility, and reconfigurability to radio frequency 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 radio frequency 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. The presented technique is applicable to scheduling any sequence of processing blocks characterized by a throughput, resource occupation and performance tabulated as a function of configuration characteristics, as is the case for filters with their coefficients and resolution yielding rejection and the number of multipliers
Passive RADAR acoustic delay line sensor measurement: demonstration using a WiFi (2.4 GHz) emitter and WAIC-band (4.3 GHz)
International audienceWe demonstrate passive RADAR interrogation of passive sensors: the non-cooperative signal source is analyzed to detect time-delayed copies of the reference signal generated by the cooperative target. The acoustic sensor is designed to introduce a delay dependent on a physical quantity under investigation, so that analyzing the echoes generated by the cooperative target allows for recovering the measured quantity. We demonstrate the passive RADAR principle for probing SAW cooperative targets acting as sensors using a WiFi emitter. Furthermore in the context of aeronautical deployment, we demonstrate the interrogation of a sensor operating in the 4.2â4.4 GHz WAIC (Wireless Avionics Intra-Communication) frequency band using a noise RADAR following principles similar to those implemented in a passive RADAR approach
Digital Control of Residual Amplitude Modulation for Ultra-Stable Optical Cavity
International audienceIn this work, we present one of the main limitations of the performance of cavity stabilized laser. Optical phase modulators (EOM) are essential devices in stabilized lasers. The residual amplitude modulation (RAM) generated by its EOM is partly due to the mismatch between the polarization axis of the laser beam and the extraordinary axis of the modulator. Using digital control system, we have developed a simple and robust technique for an active reduction of the RAM. It is based on temperature control and the addition of a DC offset on an EOM and it reduces the RAM to a few 0.25 ppm
Residual amplitude modulation at the level for ultra-stable lasers
The stabilization of lasers on ultra-stable optical cavities by the
Pound-Drever-Hall (PDH) technique is a widely used method. The PDH method
relies on the phase-modulation of the laser, which is usually performed by an
electro-optic modulator (EOM). When approaching the level, this
technology requires an active control of the residual amplitude modulation
(RAM) generated by the EOM in order to bring the frequency stability of the
laser down to the thermal noise limit of the ultra-stable cavity. In this
article, we report on the development of an active system of RAM reduction
based on a free space EOM, which is used to perform PDH-stabilization of a
laser on a cryogenic silicon cavity. A RAM stability of is
obtained by employing a digital servo that stabilizes the EOM DC electric
field, the crystal temperature and the laser power. Considering an ultra-stable
cavity with a finesse of , this RAM level would contribute to
the fractional frequency instability at the level of about ,
well below the state of the art thermal noise limit of a few .Comment: 6 pages, 4 figure