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Radio frequency identification tags (RFID) have been in use for a number of years, in a variety of applications. They are a small computer chip like device that can range in size from a thumbnail to a credit card size device. They consist of a small silicon chip, and an antenna used to receive and transmit data. When a tag receives a signal from a valid reader it sends a response, typically a tag ID and any other requested/available data back to the reader device. The newer range of RFID chips that are coming into use now use higher frequencies (UHF) and are able to be detected, or transmitted to, from longer distances (1 – 10 m) with a conventional handheld reader. This increased distance alone presents many opportunities for users and misusers alike. These include but are not limited to passive scanning/sniffing of information in transit, deception, disruption of signal, and injection of malicious or false data into the broadcast envelope. There is no evidence currently in the literature of long-range scans or attacks on UHF RFID tag or supporting infrastructure. Given that these tags are now being used in military applications, an improved understanding of their vulnerabilities from long range scanning techniques will contribute to national security. An understanding of the long range scanning potential of these devices also will allow further study into the possible misuse of RFID technology in society by governments, business and individuals.

Proceeding of: 4th International Electronic Conference on Sensors and Applications (ECSA-4) ; Spatial localization of emitting sources is especially interesting in different fields of application. The focus of an earthquake, the determination of cracks in solid structures or the position of bones inside a body are some examples of the use of multilateration techniques applied to acoustic and vibratory signals. Radar, GPS and wireless sensors networks location are based on radiofrequency emissions and the techniques are the same as in the case of acoustic emissions. This paper is focused on the determination of the position of sources of partial discharges inside electrical insulation for maintenance based on the condition of the electrical machine. The use of this phenomenon is a mere example of the capabilities of the proposed method because its emission can be electromagnetic in the UHF range or acoustic when the insulation is immersed in oil. Generally, when a pulse is radiated from a source, the wave will arrive to two receivers at different times. One of the advantages of measuring these time differences of arrival or TDOA is that it is not required a common clock as in other localization techniques based on the time of arrival (TOA) of the pulse to the receiver. With only two sensors, all the possible points in the plane that would give the same TDOA describe a hyperbola. Using an independent third receiver and calculating the intersection of the three hyperbolas will give the position of the source. Therefore, planar localization of emitters using multilateration techniques can be solved at least with three receivers. This paper presents a method to locate sources in a plane with only two receivers, one of them in a fixed position and the other is placed describing a circumference around the first one. The TDOA are measured at different angles completing a total turn and obtaining a function, angle versus TDOA, that has all the geometric information needed to locate the source. ; The work done in this paper has been funded by the Spanish Government under contract DPI2015-66478-C2-1-R (MINECO/FEDER, UE)

Partial discharges (PD) measurement is a well-known technique for judgment of the condition of power transformer offline. Phase-resolved PD measurement is a normalized technique for PD tests, but noise, especially by PD-measurements onsite is sometimes difficult to reject, and a post-processing of a pattern is necessary to separate different sources. Higher-frequency-detection devices and processing strategies are useful for PD classification and identification. Recently, ultra-high-frequency (UHF) detection by means of antennas has been shown to be a promising detection system for both offline and online PD-measurements. However, it is necessary to assess whether PD source separation and classification is possible by means of pulse analysis because some additional UHF noise sources are coupled to the detected signals, and it is not clear whether different sources produce different pulses. In this study, the attenuation effect of the metallic tank of a power transformer on the inner PD activity when measured outside the tank was studied. Additionally, experiments were conducted to detect and characterize two different PD sources (internal and external discharges) using two antennas measuring the same phenomenon inside and outside of a transformer. It will also be shown that broadband UHF signals are useful for PD recognition and that a deep study of frequencies below 500 MHz can separate PD occurring inside from those occurring outside when measured with an antenna outside the tank. ; This research has been supported by the Spanish Science and Technology Ministry under contract DPI 2009-14628- C03-02 and by the Madrid Regional Government and Universidad Carlos III de Madrid under contract CCG10- UC3M/DPI-4627. Tests have been made in the High Voltage Research and Tests Laboratory of Universidad Carlos III de Madrid (LINEALT). ; Publicado

Passive millimeter-wave remote sensing for enhanced vision: For many military or peace-keeping operations it is necessary to provide better situational awareness to the commander of a vehicle with respect to possible threats in his local environment (predominantly ahead), at a distance of a few ten to a few hundred meters. As a beneficial part of a suitable multi-sensor system, an imaging radiometer with a sufficiently high frame rate and field of view is considered and will be presented in the briefing. The radiometer, working 24 hours in all weather and sight conditions, generates quasi-optical images simplifying the microwave image interpretation. Furthermore it offers the advantage to detect and localise objects and persons under nearly all atmospheric obstacles and also extents the surveillance capabilities behind non-metallic materials like clothing or thin walls and thin vegetation. Based on constraints of low costs and the observation of a large field of view, the radiometer still offers a moderate resolution at a moderate scan speed. Active microwave remote sensing for buried object detection: Many countries face the problem of landmines and unexploded ordnance contaminated land sections which present a significant risk to the civilian population. The detection and subsequent clearance of these explosive hazardous substances is therefore extremely important and necessary. Within the framework of an EU project called TIRAMISU (Toolbox Implementation for Removal of Anti-personnel Mines, Sub-munitions and UXO) a ground-based, near field broadband multi-element radar system (called TIRAMI-SAR) using the synthetic aperture method is being developed. TIRAMI-SAR is based on the SAR principle for the medium range detection of mines at several meters average distance. The truck based radar system operates under a side-looking geometry in the range direction (i.e. cross-track direction) with the method of pulse compression. Using an operational bandwidth of round about 2.7 GHz, a spatial range resolution of 5-10 cm can be achieved. In the along-track direction (i.e. in motion or azimuth direction), the method of synthetic aperture radar (SAR) leads to a similarly high spatial resolution (azimuth resolution). The selected UHF range represents a good compromise between the penetration depth of the electromagnetic waves and the practical size of usable, broadband antennas. With this setup it is possible to scan an area of approx. 50 m² (e.g. 5 m across track, > 10 m along track) in round about 3 minutes. Using nearly arbitrary geometries for the mono-static and bi-static antenna arrangement in combination with polarimetry information for improved detection and localization, it is possible to produce multiple two-dimensional (2D) SAR images and by incoherent or coherent superposition a type of three-dimensional (3D) SAR images as well.

In this paper, we present a new digital baseband processor for UHF tags. It is a low-power and low-voltage digital circuit and adopts the Chinese military standard protocol GJB7377.1. The processor receives data or commands from the RF front-end and carries out various functions, such as receiving and writing data to memory, reading and sending memory data to the RF front-end and killing tags. The processor consists of thirteen main sub-modules: TPP decoding, clock management, random number generator, power management, memory controller, cyclic redundancy check, FM0 encoding, input data processing, output data processing, command detection module, initialization module, state machine module and controller. We use ModelSim for the TPP decoding simulation and communication simulation between tag and reader, and the simulation results meet the design requirements. The processor can be applied to UHF tags and has been taped out using a TSMC 0.18 um CMOS process.

The FOPEN radar uses frequencies at VHF and UHF to penetrate the foliage of trees or buildings and detect bodies and people hiding under their cover. FOPEN is an important technology, being located on airborne and ground-based platforms and designed to aid surveillance of very large areas, especially those areas rich in vegetation, which are unsuitable for detection and identification using other sensors. The information the FOPEN radar provides ensures the necessary support for civil or military activities. The civilian use of FOPEN ensures the fulfillment of surveillance and monitoring missions of the Earth's surface. The data provided will ensure the study of biodiversity, forests, land surface, etc. through the potential of this radar to detect bodies under the canopy of trees.The military use of FOPEN ensures the detection of enemy forces and assets concealed under foliage, whether they are moving or not. The images generated by FOPEN ensure the detection of targets by electromagnetic waves penetrating foliage or buildings, countering adversary camouflage, concealment, or deception techniques. The data provided by FOPEN ensures the necessary information support for decision-making processes during mission planning and execution.

This work presents an enhanced autonomous airborne Synthetic Aperture Radar (SAR) imaging system able to provide full 3D radar images from the subsurface. The proposed prototype and methodology allow the safe detection of both metallic and non-metallic buried targets even in difficult-to-access scenarios without interacting with the ground. Thus, they are particularly suitable for detecting dangerous targets, such as landmines and Improvised Explosive Devices (IEDs). The prototype is mainly composed by an Ultra-Wide-Band (UWB) radar module working from Ultra-High-Frequency (UHF) band and a high accuracy dual-band Real Time Kinematic (RTK) positioning system mounted on board an Unmanned Aerial Vehicle (UAV). The UAV autonomously flies over the region of interest, gathering radar measurements. These measurements are accurately geo-referred so as to enable their coherent combination to obtain a well-focused SAR image. Improvements in the processing chain are also presented in order to deal with some issues associated to UAV-based measurements (such as non-uniform acquisition grids) as well as to enhance the resolution and the signal to clutter ratio of the image. Both the prototype and the methodology were validated with measurements, showing their capability to provide high-resolution 3D SAR images. ; This research was funded by the Ministerio de Educación—Gobierno de España under Grant FPU15/06341; by the Ministerio de Ciencia, Innovación y Universidades—Gobierno de España under Project RTI2018-095825-B-I00 ("MilliHand"); by the Government of the Principality of Asturias (PCTI) and European Union (FEDER) under Grant IDI/2018/000191; and by the Instituto Universitario de Investigación Industrial de Asturias (IUTA) under Project SV-19-GIJON-1-17 ("RadioUAV").

An increasing amount of interest has been evolved in VHF/UHF SAR applications. These radars have proven to be a very powerful method for underground and obscured object detection. Emerging civilian and military applications of VHF-UHF radar systems include the detection of targets concealed by foliage and/or camouflage, detection of buried objects, and archeological and geological exploration. However the VHF/UHF portion of the spectrum is heavily used for commercial as well as military purposes. The interference power received from the emitters often exceeds the power of the received radar signal by many dB, thereby limiting the systems sensitivity. Two main approaches for the removal of RF interferences can be found at the literature: coherent estimation and subtraction approaches and incoherent spectral or time domain filter approaches. Only some of these approaches are proven to be phase preserving for interferometric SAR data applications. In this paper we address the Least Mean Square (LMS) method for estimation and coherent subtraction of the RF Interference in interferometric SAR data applications. We also compare the results with a phase preserving Notch Filter. For this purposes we use polarimetric interferometric SAR data from the test site in Solothurn/Switzerland collected by the DLR's Experimental SAR (ESAR).

Spatial localization of emitting sources is especially interesting in different fields of application. The focus of an earthquake, the determination of cracks in solid structures, or the position of bones inside a body are some examples of the use of multilateration techniques applied to acoustic and vibratory signals. Radar, GPS and wireless sensors networks location are based on radiofrequency emissions and the techniques are the same as in the case of acoustic emissions. This paper is focused on the determination of the position of sources of partial discharges in electrical insulation for maintenance based on the condition of the electrical equipment. The use of this phenomenon is a mere example of the capabilities of the proposed method but it is very representative because the emission can be electromagnetic in the VHF and UHF ranges or acoustic. This paper presents a method to locate more than one source in space with only two receivers, one of them in a fixed position and the other describing a circumference around the first one. The signals arriving from the different sources to the antennas are first separated using a classification technique based on their spectral components. Then, the individualized time differences of arrival (TDOA) from the sources collected at different angles describe a function, angle versus TDOA, that has all the geometric information needed to locate the source. The paper will show how to derive these functions for any source analytically with the position of the source as unknown parameters. Then, it will be demonstrated that it is possible to fit the curve with experimental measurements of the TDOA to obtain the parameters of the position of each source. Finally, the technique is extended to the localization of the emitter in three dimensions. ; The work done in this paper has been funded by the Spanish Government (MINECO) and the European Regional Development Fund (ERDF) under contract DPI2015-66478-C2-1-R (MINECO/FEDER, UE).

Hysteresis in power amplifiers (PAs) is investigated in detail with the aid of an efficient analysis method, compatible with commercial harmonic balance. Suppressing the input source and using, instead, an outer-tier auxiliary generator, together with the Norton equivalent of the input network, analysis difficulties associated with turning points are avoided. The turning-point locus in the plane defined by any two relevant analysis parameters is obtained in a straightforward manner using a geometrical condition. The hysteresis phenomenon is demonstrated to be due to a nonlinear resonance of the device input capacitance under near optimum matching conditions. When increasing the drain bias voltage, some points of the locus degenerate into a large-signal oscillation that cannot be detected with a stability analysis of the dc solution. In driven conditions, the oscillation will be extinguished either through synchronization or inverse Hopf bifurcations in the upper section of the multivalued curves. For an efficient stability analysis, the outer-tier method will be applied in combination with pole-zero identification and Hopf-bifurcation detection. Departing from the detected oscillation, a slight variation of the input network will be carried out so as to obtain a high-efficiency oscillator able to start up from the noise level. All the tests have been carried out in a Class-E GaN PA with measured 86.8% power-added efficiency and 12.4-W output power at 0.9 GHz. ; This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO) under Project TEC2014-60283-C3-1-R and Project TEC2014-58341-C4-1-R, with FEDER co-funding, the Parliament of Cantabria (12.JP02.64069) and by the Predoctoral Fellowship for Researchers in Training of the University of Cantabria and the Regional Ministry of Education of the Government of Cantabria.

In military environments, especially land field, high frequencies (HF, 3 - 30 MHz), very high frequencies (VHF, 30 - 300 MHz) and ultra high frequencies (UHF, 300 - 3000 MHz) have been used for long range and shortrange communications, for communication interference or for detection. To have all those functions on the same carrier, they require many antennas, therefore they are increasing the operator's electromagnetic overexposure risk. Civilian and military standards were published providing limits on external electromagnetic fields and dosimetric quantities (specific absortion rate SAR, current density and internal electric field) to limit this overexposure risk between 0 and 300 GHz. The PhD thesis project has two main objectives. First, civilian and military standards are studied to understand how they were developed and if they are really suited for HF and VHF frequencies. Second, a new validation method of Thales radio product is proposed and validated. This PhD thesis project have characterized numerically the human body electromagnetic and thermal behavior during electromagnetic exposure in HF and VHF. Then, by studying couplings between external electromagnetic fields, induced current and human body, formulas to calculate both whole-body averaged SAR and local SAR 10 g in homogeneous body are proposed for the first time. ; Dans les environnements militaires, et plus particulièrement dans le domaine terrestre, de nombreux systèmes radioélectriques HF (de 3 à 30 MHz), VHF (de 30 à 300 MHz) et UHF (de 300 à 3000 MHz) sont utilisés. Ces systèmes remplissent plusieurs fonctions (communication longue et courte distance, brouillage, radar, etc .) et peuvent parfois cohabiter sur un même porteur. Ces différentes fonctions utilisent plusieurs antennes et augmentent les risques de surexposition électromagnétique des opérateurs. Des normes civiles et militaires proposent des limites sur les champs électromagnétiques appliqués et sur des grandeurs dosimétriques (débit d'absorption spécifique DAS, densité de ...

In military environments, especially land field, high frequencies (HF, 3 - 30 MHz), very high frequencies (VHF, 30 - 300 MHz) and ultra high frequencies (UHF, 300 - 3000 MHz) have been used for long range and shortrange communications, for communication interference or for detection. To have all those functions on the same carrier, they require many antennas, therefore they are increasing the operator's electromagnetic overexposure risk. Civilian and military standards were published providing limits on external electromagnetic fields and dosimetric quantities (specific absortion rate SAR, current density and internal electric field) to limit this overexposure risk between 0 and 300 GHz. The PhD thesis project has two main objectives. First, civilian and military standards are studied to understand how they were developed and if they are really suited for HF and VHF frequencies. Second, a new validation method of Thales radio product is proposed and validated. This PhD thesis project have characterized numerically the human body electromagnetic and thermal behavior during electromagnetic exposure in HF and VHF. Then, by studying couplings between external electromagnetic fields, induced current and human body, formulas to calculate both whole-body averaged SAR and local SAR 10 g in homogeneous body are proposed for the first time. ; Dans les environnements militaires, et plus particulièrement dans le domaine terrestre, de nombreux systèmes radioélectriques HF (de 3 à 30 MHz), VHF (de 30 à 300 MHz) et UHF (de 300 à 3000 MHz) sont utilisés. Ces systèmes remplissent plusieurs fonctions (communication longue et courte distance, brouillage, radar, etc .) et peuvent parfois cohabiter sur un même porteur. Ces différentes fonctions utilisent plusieurs antennes et augmentent les risques de surexposition électromagnétique des opérateurs. Des normes civiles et militaires proposent des limites sur les champs électromagnétiques appliqués et sur des grandeurs dosimétriques (débit d'absorption spécifique DAS, densité de courant et champs électriques internes) pour limiter ces risques entre 0 et 300 GHz. Ces travaux de thèse ont deux objectifs principaux. Le premier est d'étudier les normes civiles et militaires afin de comprendre comment elles ont été développées et si elles sont réellement adaptées aux fréquences HF et VHF. Le deuxième est de proposer et valider une nouvelle méthode de validation des produits radio Thales. Pour cela, nous caractérisons numériquement le comportement électromagnétique et thermique du corps humain lors d'une exposition électromagnétique en bandes HF et VHF. L'étude des couplages entre le corps et les champs électromagnétiques externes nous permet de proposer pour la première fois des formules calculant les DAS dans le corps d'un fantôme homogène à partir, soit des courants induits le long du corps pour une exposition quelconque, soit du champ électrique appliqué pour une exposition en onde plane.

International audience We present a datalogger based on Arduino cards and commercially available tools for radio frequency identification, which we term the e-RFIDuino. Designed to be robut, easy to build and install, it detects and records the mobility of objects tagged with active transponders emitting in the ultra-high frequency domain (433.5 MHz). It functions without connection to the power supply network and is adapted to harsh outdoor environments. Once installed in the field and its on-site sensing field is determined, the data collected (timestamp of detection, transponder identification number, and received signal strength indication) allow estimation of the virtual velocity of tracer passage and investigation of displacement patterns at the scale of the area of detection. Experimental tests showed the device to have very high effectiveness when used to monitor the passage of sediment tracers in a torrential river system during various flood events over several months. The total cost to construct this open source device is below 850 Euros, and it is easily customizable. In the future, it could be equipped with a system for data transmission over the mobile telephone network to reduce the field effort and time required to obtain data, and to provide real-time triggering of field acquisitions at the most appropriate times