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International audience; This paper describes the design and development of a highly directive planar end-fire array using arc dipoles as the array elements. The inter element spacing, shape, and size of the array elements are optimized for maximum directivity and gain. The array is printed on a substrate whose dimensions are also optimized for better performance. The overall length of the proposed six element array is 1.9λ, giving directivity and gain values as 12.0 dBi and 10.2 dB respectively at 5.8 GHz.

This paper proposes an improved model for the nonlinear behavior of the components of Radio-over-Fiber (RoF) links focusing here on the laser source. In a previous work, it was shown with a flexible new opto-microwave design approach a first behavioral model of RoF links that exploited the hyperbolic tangent function (the so-called tanh model) to model the highpower nonlinearities. Since this was not sufficient to simulate adequately all the nonlinearities, in this work, for the first time in the authors’ knowledge, the improved nonlinear model based on Cann’s model is developed, on an electro optic transducer. Then the amplitude-to-amplitude conversion of the link is better taken into account with the introducing of nonlinear properties of the link at high input power in the model. The new transfer equation includes several parameters that can be adjusted to adapt the model to any of the components, especially the photo-emitters under study, which are the main cause of this type of nonlinear behavior of the system. In particular, this improved model is applied on the state-of-the-art 850 nm GaAs Vertical Cavity Surface Emitting Laser (VCSEL), simulating several Figures of Merit such as the Error-Vector Magnitude (EVM) of a Long Term Evolution (LTE) signal with a Quadrature Phase Shift Keying (QPSK)and the output amplitude-modulated power versus input amplitude-modulated power, also called AM/AM curve. This new proposed nonlinear model outperforms other existing behavioral models and its non linear simulation better fits with the measurements. Finally, we conclude that the performance improvement highly depends on the nonlinearity sharpness parameter, depending on the frequency and the bias current.

International audience; Indoor localization is one of the most important topics in wireless navigation systems. The large number of applications that rely on indoor positioning makes advancements in this field important. Fingerprinting is a popular technique that is widely adopted and induces many important localization approaches. Recently, fingerprinting based on mobile robots has received increasing attention. This work focuses on presenting a simple, cost-effective and accurate auto-fingerprinting method for an indoor localization system based on Radio Frequency Identification (RFID) technology and using a two-wheeled robot. With this objective, an assessment of the robot’s navigation is performed in order to investigate its displacement errors and elaborate the required corrections. The latter are integrated in our proposed localization system, which is divided into two stages. From there, the auto-fingerprinting method is implemented while modeling the tag-reader link by the Dual One Slope with Second Order propagation Model (DOSSOM) for environmental calibration, within the offline stage. During the online stage, the robot’s position is estimated by applying DOSSOM followed by multilateration. Experimental localization results show that the proposed method provides a positioning error of 1.22 m at the cumulative distribution function of 90%, while operating with only four RFID active tags and an architecture with reduced complexity.

International audience; This paper proposes an improved mathematical formulation of Johnston’s approach tomeasure the radiation efficiency of an antenna, based on the Wheeler Cap (WC) technique. Theproposed modifications allow the measurement of the radiation efficiency of small antennas matched tocomplex loads implemented on Radio Frequency IDentification (RFID) tags. The studied structure is alow-cost, silver-printed, differentially-fed RFID dipole antenna. The antenna is printed on a flexible PET(polyethylene terephthalate) paper that is conformable on various objects. Link budget measurementsvalidate the accuracy of the formulation, which can be applied to any dipole antenna matched to anRFID chip with a complex input impedance.

Indoor localization has recently witnessed an increase in interest due to its wide range of potential services. Further, the location information is very important in many applications, such as the Internet of Things, logistics, library management and so on. Hence, different technologies and techniques have been proposed in the literature for indoor localization systems. Most of these systems present the disadvantages of a poor performance, low accuracy and high cost. However, thanks to its low cost, high accuracy and non-line-of-sight detection, radio frequency identification (RFID)-based localization has increasingly become the most used technology for indoor localization. In this paper, we propose an innovative approach based on the multiple input single output (MISO) protocol to improve the accuracy of a low-cost RFID localization system. Whereas most traditional systems use a single tag for localization, the proposed architecture encourages the use of a group of RFID tags named as a constellation. According to experimental results and based on the signals&rsquo, diversity, the location accuracy is improved to get an estimated position error of 81 cm at the cumulative distribution function of 90%.

Electromagnetic coupling between randomly distributed dipole antennas is analyzed statistically. The impedance matrix of a set of dipoles is first calculated with both the induced electromotive force (IEMF) technique and numerical electromagnetic code (NEC) simulator. Then, the input impedance of a surrounded dipole is assessed for any loading of the surrounding dipoles. Cumulative distributed functions for the mismatch of a surrounded dipole are given for different dipole densities and loadings of the surrounding dipoles. This statistical approach is proposed in the context of UHF radio frequency identification (RFID) use cases where tag antennas are concentrated in reduced volumes and the antenna group behavior should be considered.

A chiral metamaterial (MTM) is analyzed using two modal analysis methods: characteristic mode analysis (CMA) and Eigenmode expansion method (EEM). Chiral MTMs are commonly associated to antennas and other microwave devices due to their ability to interact with electromagnetic waves and alter their polarizations. Here, the interaction of a chiral helix with linearly polarized electromagnetic plane waves is studied and asymmetric transmission is demonstrated. The different metrics given by CMA and EEM are analyzed and compared. It is shown that the modal weighing coefficient is a good metric to analyze the chiral properties of the MTM, and these results are validated using a full-wave approach. It is also shown that if the two modal approaches propose very close results qualitatively, the maximum value of the modal current density obtained by EEM is closer to the one obtained by full-wave simulations. The modal approaches presented to analyze chiral MTM can be applied for the analysis of circularly polarized chiral MTM-inspired antennas.

This paper investigates the near-ground propagation and the condition under which the wave propagation can profit from the proximity of an interface. To this aim, asymptotic approximations of the electric field radiated by an elementary vertical electric dipole over a half-space are introduced. The asymptotic formulations coincide with other approximations previously carried out in the literature. In this comprehensive formulation, in addition to the direct and reflected wave, a third field component is taken into account, physically originated by the diffraction at the interface of the two media. This component, ignored by ray-based techniques, can become predominant and stimulate the near-ground propagation. This paper presents an analytical expression for the condition under which a near-ground propagation can benefit from the special component. Two critical distances associated with the beginning and the end of the preponderance zone of the component are also evaluated. The benefits of the near-ground wave propagation as well as the validity of the three analytical expressions have been verified in the frame of various scenarios.

International audience; We present in this paper a comparative study of two classifiers, namely, SVM (support vector machine) and KNN (K-Nearest Neighbors), which we combine to MFCC (Mel-Frequency Cepstral Coefficients) in order to make possible the detection of chainsaw's sounds in a forest environment. Optimization's calculation of the relevant characteristics of the sounds recorded in the forest and the judicious choice of the key parameters of the classifiers allows us to obtain a true positive rate of 95.63% for the SVM-LOG-KERNEL and 94.02% for the KNN. The SVM-LOG-KERNEL classifier offers a better classification result and a processing time 30 times faster than KNN.

This paper describes the design of a battery-assisted Ultra-High Frequency (UHF) Radio-Fre- quency IDentification (RFID) tag suitable for embedding in concrete materials and its measurement in a mortar slab. The device is built to communicate wirelessly not only the ID number of the RFID chip but also the digitalized output of a strain gauge sensor. Design optimizations of the RFID antenna is based on published permittivity and conductivity values of concrete. Experimental read ranges are measured from 800 to 1000 MHz with the help of commercial test equipment. Reading is possible up to 50 cm from the surface of a mortar block for a tag embedded 5 cm below the surface. This result is the first published one for RFID tags embedded in concrete or mortar.

A MEMS electrostatic kinetic energy harvester (e-KEH) of about 1 cm2, working at ultralow frequency (1–20 Hz), without any supported additional mass on its mobile electrode, and working even without a vacuum environment is reported. The prototype is especially suitable for environments with abundant low frequency motions such as wearable electronics. The proposed e-KEH consists of a capacitor with a finger-teeth interdigited comb structure. This greatly reduces the air damping effect, and thus the capacitance variation remains important regardless of the presence of air. With the new design, the energy transduced per cycle of excitation is no less than 33 times higher than the classic design within 10–40 Hz/2 gpeak, while is 85 times higher at 15 Hz/2 gpeak. An enclosed miniature ball combined with non-linear stoppers enables the oscillation of the movable electrode through impact-based frequency up-conversion mechanism, which is also improved by the low air damping. Thanks to this new design, a higher efficiency than the classic gap-closing comb structure is obtained, as a larger range of working frequency (1–180 Hz) in air. A maximum energy conversion of 450 nJ/cycle is obtained with a bias voltage of 45 V and an acceleration of 11 Hz, 3 gpeak. Working with a diode AC-DC rectifier, the proposed KEH is able to support up to 3 RFID communications within 16 s while operated at 11 Hz, 3 gpeak.

This communication describes the embedding of UHF RFID tags dedicated to power supply cords. A general purpose commercial RFID module is coupled to microstrip dipoles to realize tags, which are wrapped and taped around the cords. The tag dimensions are optimized for a maximum power transmission to the chip and a maximum reading distance in the presence of the cord. Experimental read ranges of the order of 5 m are obtained, whereas commercial tag outperforming the optimized tag in free-space only performs well at 2 m on power cords.

International audience; We report an energy-autonomous Radio Frequency IDentification (RFID) tag system which is powered by an electrostatic MEMS-based Vibration Energy Harvester (e-VEH). The VEH is designed specifically for the vibrations of low frequency around 10 Hz. An energy of 80 nJ/cycle can be delivered when the VEH is loaded with an optimal resistor and a bias of 20 V. An RFID chip is powered by the current released from a 1-μF capacitor, which is charged by the VEH through a diode rectifier. The read range of the tag is increased from 2.5 m (under batteryless mode) to 15 m when powered by the VEH working with an acceleration of 2 grms and 10 Hz. The energy of the VEH stored in the capacitor within 40 s can sustain up to 3 tag readings.

The proposed model of the human torso is principally a host sphere, filled with muscle tissue, wherein three eccentric spherical inclusions are accommodated. Two of them are twins and represent the lungs, whereas the third, referred to as the abdomen, represents all human organs beneath the diaphragm. The host sphere is surrounded by two concentric layers, which represent skin and fat. The dyadic Green's function (dGf) of this nonspherical body is determined by application of the principle of superposition and by enforcement of the boundary conditions on all interfaces. The outcome is a set of linear equations for the vector wave amplitudes of the dGF, and that set is solved by truncation and matrix-inversion. Once this is done, the dGf is available as a sum of dyads, and the electric-field intensity can be determined by integration of the dGf, dot multiplied by the current density of the source. The numerical results correspond to an electric Hertz dipole placed near the waist, i.e., the equator of this torso model, and radiating at a WiFi frequency. Plots of the electric-field intensity along the waist and field maps across the equator plane manifest how protected the internal organs are from the external point source, which is practically attached to the surface, and how sensitive to internal organs is the field on the waist.

Radiation from an encapsulated Hertz dipole, eccentrically implanted in a layered spherical body, is determined by use of the dyadic Green’s function (dGf) theory. The body, a model of the human torso, comprises skin and fat layers around a homogeneous tissue core. The capsule is a spherical cavity bounded by an insulating layer. The dGf of this radiation problem involves two reference points, the center of the body and the center of the capsule. The analysis results in a concise formulation of the dGf and of the main radiation quantities. Numerical results are shown for the radiated power, efficiency, and directive gain of the Hertz dipole versus the capsule displacement from the center of the body. Specific absorption rate (SAR) maps are drawn on two cross sections of the body in search of the entire distribution of SAR and the location of peak SAR.

A high-temperature tolerant pattern diversity antenna is presented for body wearable applications in hostile conditions. The proposed system consists of a dielectric resonator antenna (DRA) placed at the centre of a slot loop antenna. The combination yields pattern diversity with broadside and endfire radiation patterns from slot loop and DRAs, respectively. The antenna system offers common bandwidth of 4.95% with port isolation of better than 13 dB at 2.4 GHz. The thermal characteristics of antenna have been studied for high-temperature operation and no discernible change in the radiation behaviour is noted. The antenna undergoes 2% resonant frequency shift when operated at elevated temperature. The antenna diversity has been measured for three on-body communication channels. The antenna offers 9.5 dB diversity gain in a pure non-line-of-sight channel surrounded by a rich fading environment subjected to the selection combining scheme. The antenna has dimensions of 0.4λo × 0.4λo × 0.1λo .

International audience; A new procedure to measure the apparent reflection coefficient ofdifferential patch antennas at 60 GHz is described. The measurementmethod makes use of two WR15/microstrip-line (MSL) transitionswhich are simple to realise. The experimental results are comparedwith simulated results. This comparison emphasises the limited effectof transition losses on measurement accuracy.

International audience; A simple topology is described for radio frequency identification(RFID) tags mountable on metal surfaces. The tag is built around acommercial UHF RFID module combining an IC and a couplingloop. The module is placed in the neighbourhood of a slot which isused both to couple the energy from the module to the patch-likeantenna and to miniaturise the tag. A read range of almost 4 m isobtained in the 865–868 MHz band with a 1.6 mm low-cost FR4substrate.

International audience; RFID systems are characterized by a changing environment which perturbs and degrades the performances of each system component. Passive tag antennas are the most affected by these variations, the tag functionalities vary by changing the surface where it is attached and in some case even the content of boxes or recipients has an influence. A combined antenna is designed in order to ensure a read range for a plastic recipient containing water or not. Before, two particular antennas are proposed to work in each case, both situations are analyzed separately to observe their performances and extract their advantages to join them in one unique structure less sensitive within a limited read range

International audience; A compact dual pattern diversity antenna combining a slot loop and a dielectric resonator antenna (DRA) is presented for body area network (BAN) applications at 2.4 GHz. A common bandwidth of 1.5% is obtained with an isolation of -12dB. The slot loop provides slightly asymmetric broadside radiation patterns while purely symmetric end-fire type radiation patterns are obtained with the DRA. The diversity gain performance of the antenna has been tested in receiving mode for three different on-body communication channels.

International audience; A theoretical method based on the induction equivalence principle and Green's functions is presented here to calculate the scattered electromagnetic fields from exterior plane building facades in urban environment. The reflection coefficient of the whole inhomogeneous structure can be calculated for different incidence angles. The derivation of appropriate Green's functions is presented. The method takes into account the large-scale discontinuities on the facade. It is simple to implement and fast to obtain results because of the absence of poles in the Green's functions expressions. The accuracy of the method is discussed comparing to a commercial software and physical optics as another method based on equivalent currents. The article concludes with a statistical study on the influence of concrete permittivity variation on the reflection coefficient of a concrete-glass building facade.

International audience; Reduction of specific absorption rate (SAR) has now become a buzz word because of the growing health concerns over microwave exposure. Ferrites are found to be effective in diminishing electromagnetic influence. In this reported work, flexible polymeric ferrite sheets are characterised on the basis of their shielding efficiencies. SAR measurements are carried out with a planar wearable antenna and polymeric ferrite shielding to confirm its competence.

A reconfigurable parasitic patch array is designed to provide polarization and pattern diversities. The performance of the device is predicted using a commercial simulator including a pin diode modelling and an optimization procedure of the switched loads based on an equivalent flow graph. Measurements of the correlation factor and the diversity gain in an indoor environment are performed with a dedicated platform for two orientations of the antenna.

International audience; This paper describes the design rules of a compact microstrip patch antenna with polarization reconfigurable features (right-handed circular polarization (CP)/left-handed CP). The basic antenna is a circular coplanar-waveguide (CPW)-fed microstrip antenna excited by a diagonal slot and the CPW open end. This device is developed for short-range communications or contactless identification systems requiring polarization reconfigurability to optimize the link reliability. First, experimental and simulated results are presented for the passive version of the antenna excited by an asymmetric slot. A reconfigurable antenna using beam-lead p-i-n diodes to switch the polarization sense is then simulated with an electrical modeling of the diodes. Finally, the efficiency reduction resulting from the diode losses is discussed.

A micro-electro-mechanical series (MEMS)-switched parasitic antenna array providing radiation pattern diversity is described. A new modeling method is introduced in order to allow a fast and accurate optimization of the antenna. This method is demonstrated with the design of both passive and active prototypes at 5.6 GHz. The active prototype makes use of stand-alone packaged MEMS switches. Measured return loss and radiation patterns are in good agreement with the design, demonstrating a beam-switching at plusmn25deg

A new method is presented to estimate the loss resistance of antennas located slightly above a lossy medium. This technique is more specifically developed for the context of body area networks. This method is based on the estimation of the antenna resistance above the medium and above a perfect electric conductor.

International audience; A circular patch antenna fed by a coplanar waveguide (CPW) line is proposed to obtain circular polarisation (CP). The CP results from the combined excitation of the patch by an inclined slot (integrated in the CPW feedline) and the CPW feedline termination. The asymmetrical characteristics of the excitation involve the excitation of both the odd and the even modes in the CPW line.

Two radiating spirals stacked on a foam substrate are used in the design of a circularly polarized antenna designed to respect new bandwidth constraints resulting from the emergence of multimedia services in satellite communications. Orthogonal circular polarizations are required for up and down links over large frequency bandwidths. In the single antenna, 4 to 5% axial ratio (AR) bandwidths are observed in a large beamwidth for both bands. This AR bandwidth increases appreciably (24 to 31%) when two antennas are combined in a sequentially rotated configuration.

International audience; A new type of foam is proposed as a basic substrate for printed arrays operating in the X-band and above. As an example, 2×2 and 4×4 circularly polarised (CP) microstrip arrays are designed at 11 GHz showing an axial ratio (AR) bandwidth greater than 10% with excellent gain and return loss performances

International audience; The authors present the design of a wideband circularly polarised antenna with switchable polarisation sense. The basic antenna is a circularly polarised aperture coupled patch antenna with a slot excitation located along the diagonal of a rectangular patch. A second slot is added along the other diagonal and beam-lead pin diodes are inserted in both slots to allow a dual sense operation for a compact structure in a 4% CP bandwidth.

A numerical modeling based on the solution of coupled integral equations is used for the characterization of CPW-fed aperture-coupled microstrip antennas. Various shapes of excitation slots, such as open stubs, slot loops, and capacitively and inductively coupled slots, are investigated in terms of return loss and front-to-back radiated power ratio. It is shown that a centered CPW open stub gives a minimum of back radiation while allowing for easy matching. The slot-loop excitation seems to be a convenient feeding mechanism that also allows the insertion of active devices.

The use of active microwave solid state devices providing localized power drive for planar antenna elements has simulated interest over the past few years particularly for low cost phased array radar, spatial power combiner and automatic vehicle tolling applications. This article describes two oscillators that use a CPW-fed microstrip antenna not only as the radiating element, but also as the output resonating load which determines the oscillation frequency. The antenna is excited by an inductively coupled slot for the first oscillator and a slot-loop for the second oscillator. As CPW lines make connection of active components easier, they have been chosen for the feeding of the excitation slots. Since it facilitates the DC bias isolation, a microstrip antenna excited by a slot-loop is proposed as a compact and easy-to-fabricate oscillating antenna with a small number of soldering points and no via holes, unlike oscillating antennas fed by microstrip lines.

A microstrip antenna fed by a conductor backed coplanar waveguide is demonstrated. The addition of a back-side metallic ground plane involves a possible power leakage owing to the excitation of parallel plate modes (PPMs). A theoretical model, based on the solution of coupled integral equations, is validated by experimental results. It is shown that the power leakage can be avoided by a proper choice of substrate characteristics.

An oscillating slot loop antenna working at 4.02 GHz is realised with a low cost GaAs MESFET. A conductor backing is used to obtain a unidirectional radiation pattern.

The authors propose an efficient amelioration of the concept of large bandwidth aperture-coupled microstrip antennas by coupling a CPW line-fed slot to a microstrip antenna. The CPW fed aperture-coupled microstrip antenna investigated has a large bandwidth with high gain and low crosspolarisation levels, is compact with only one substrate, and may be easily connected to both passive and active components. A numerical model has been developed and the theoretical results are in good agreement with the experiments.

A metallic electromagnetic bandgap material (EBG) is realised by combining 4/spl times/4 unit cells in a square geometry and excited by a microstrip line through a slot-aperture. It is shown that this structure is a radiating one, called an EBG patch, resonating at a lower frequency than the plain patch showing the same dimensions. An analytical model for the wavenumber of the EBG material facilitates the design of the EBG patch.

A CPW-fed slot antenna including pin diodes for multifrequency operation within a frequency octave and more is presented. The use of GaAs beam-lead pin diodes limits the influence of the parasitic resistance and reactance presented by surface mount diodes. The simplicity of the structure results in a simplified and compact biasing circuit.

International audience; pin diode control is used to obtain a dual-band operation of a capacitively coupled patch antenna fed by a coplanar waveguide (CPW). The beam-lead pin diodes are inserted in the excitation slot and reduce the coupling length of the slot in their ON state. The frequency ratio of the two operating frequencies is 1.22 at 4.0 GHz. Details of the antenna design and experimental results are presented and discussed.

International audience; The influence of capacitors periodically soldered along the radiating edges of a leaky wave antenna (LWA) is described. As the propagation characteristics are modified, the main beam is tilted from the angle observed for the unloaded LWA. This property allows beam steering applications at a fixed frequency if bias-controlled reactances are used.

Injection locked oscillator arrays based on CPW-fed antennas have been realised which operate at 4 GHz. Their main characteristics are the simplicity and compactness of the design. One side of the substrate is devoted to oscillator circuitry while the other side includes the radiating elements and the injection circuit. Results concerning the beam scanning control and power performance are presented.

The authors present a small series-fed array of microstrip leaky wave antennas (LWAs) operating at 6.85 GHz and showing a narrow dual-beam pattern (17/spl deg//spl times/22/spl deg/). The excitation is provided by a slotted coplanar waveguide. This type of antenna could be used as a radar sensor in Janus systems for contactless measurements of velocity and distance.

International audience; The authors describe twin Vivaldi antennas directly fed by a coplanar waveguide. They have been designed and measured for various angles between the radiating slots. All the designs show a centred zero in the E plane with a low cross-polarisation. In the H plane they provide zeros for /spl phi/=90/spl deg/ and 270/spl deg/ and are omnidirectional for other values.