Search

This paper describes a compact and low cost optically fed antenna for using as a receiver in 5G cellular networks and in distributed antenna systems. It compares the performance of two different topologies of patch antennas tightly integrated with vertical-cavity surface-emitting lasers (VCSELs), without the need for an amplifier stage or matching circuit. Opto-microwave (OM) gain of −21.5 dB at 5.15 GHz for the Microstrip patch antenna (MPA), and −24.2 dB at 4.8 GHz for the Grounded Coplanar patch antenna (GCPA) are achieved. The MPA architecture is quite original as it removes the need for RF feed lines through a direct injection of the signal from the patch to the VCSEL. The paper evaluates the different contributions to the total gain due to the VCSEL responsivity, the coupling between the optical fiber and the VCSEL, the wire-bonding losses and the antenna gain, with the goal of optimizing the steps at which major losses occur.

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.

A preliminary proof-of-concept of an innovative system combining the technologies of Radio over Fiber (RoF) and Time Modulated Array (TMA) Antennas is proposed. Through a theoretical and experimental analysis, the straightforward realization of steerable antenna arrays for capillary indoor wireless signal distribution is demonstrated.

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.

The joint exploitation of Radio over Fiber (RoF) and Time Modulated Arrays (TMA) is proposed, showing how, particularly within In-Building scenarios, it allows to combine the pervasiveness of the first technique with the beam-steering capability of the second. A cost-effective 3-element RoF-TMA system is presented and investigated, to realize a solution for small offices / private houses (SoHos). It is confirmed that bringing the feed to the antennas through the RoF system keeps the possibility for the TMA to radiate power at different frequencies, in each case with a steerable maximum direction. Referring to mobile signals with RF carriers of few GHz, it is shown that to guarantee, for each of the multiple beams emitted by the TMA, a maximum deviation of 5 from its ideal direction, it is sufficient that among the output branches of the 1:3 optical splitter utilized the length difference is maintained in the range of a few millimeters.

Commercial couplers designed for 1550nm are conveniently adopted for realizing efficient Radio-over-Fiber links operating at 850nm on the standard G.652 single mode fiber. In particular, exploiting the mode filtering properties observed in these couplers when excited at 850nm, a multi-wavelength system over the standard G.652 fiber is obtained, opening the possibility to easily integrate in currently developed infrastructures such low cost systems operating in the first optical window.

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.

14th European Conference on Antennas and Propagation (EuCAP), COPENHAGUE, DANEMARK, 15-/03/2020 - 20/03/2020; This paper presents a novel circularly polarized electrically small antenna that has been designed thanks to the Characteristic Mode Analysis (CMA). It is based on the energy compensation between two elements: a non-resonant dipole antenna and a chiral Metamaterial (MTM) in order to achieve a Circular Polarization (CP). First, the two elements are analyzed separately using CMA in order to analyze the physical behavior of both structures. Then, the inter modal coupling between the dipole and the MTM helix is studied between the different modes to propose a better understanding of the net stored energy compensation. The coupling between the two structures is through the magnetic and electric modes and it thus increases the overall efficiency. Circular polarization of the antenna is obtained through the chirality properties of the helix. The proposed antenna resonates at 2.35 GHz and has electrical sizes of $\lambda/15$, $\lambda/15$, and $\lambda/39$. The radiation pattern of the antenna is omnidirectional with a fair axial ratio for a circularly polarised antenna.

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.

This paper describes a method to achieve superdirectivity in dipole array by employing only two elements, a driven element and a shorted parasitic element. To maximize the directivity, initially the array is assumed to be fully driven and the required current excitation coefficients are calculated. Then the parasitic elements are added such that the parasitic array achieves almost the same directivity as the fully driven array when optimal loads (inductive, capacitive, short) are connected to the parasitic element. It is observed that a shorted parasitic element placed very near to the driven element could enhance the directivity to a high value. The directivity can be further enhanced by placing the elements on a trapezoidal shaped substrate. A two element parasitic dipole antenna array with a directivity of 9.17 dBi is presented.

Indoor positioning systems are used to locate people or objects inside buildings. Several technologies are used for this purpose like Infrared, Global Navigation Satellite System (GNSS), Inertial Measurement Unit (IMU), Radio Frequencies, etc. Radio Frequency IDentification (RFID) is one of these technologies. Further, interference, multipath, obstacles lead to a complex spatial propagation of the signal. This paper aims to examine the coverage of RFID tags operating at 433 MHz in two different scenarios. The first one includes a single UHF RFID tag. The second introduces a constellation of tags which is a group of tags placed over a circle. The improvement in (tag-reader) distance error while using constellation is presented. Moreover, the measurement’s procedure characterized the propagation of signals in a complex indoor environment. According to experimental validations, performance of simulations based on the 3D ray-tracing method is obviously illustrated. The measured and simulated data present a good agreement between each other; this encourages the use of the simulated propagation model for indoor localization algorithms.

UHF RFID (Radio Frequency IDentification) technologies have a long established role for tracking and identification of objects and persons. In some applications the density of RFID tags is high, this can give rise to an important electromagnetic coupling between tag antennas which modifies antenna’s key parameters, i.e., matching properties and radiation pattern. These electromagnetic modifications can alter the communication links between devices and thus degrade the read rate or the read range of an RFID system. The mutual coupling between RFID tags has been investigated in literature [1], however the statistical modelling of the impact of the mutual coupling for high densities of RFID tags is still a new topic [2].

This paper is a communication about the near-ground propagation and the condition under which the proximity of a lossy interface improves the path loss [1]. The well-known Sommerfeld half-space problem is treated by Sommerfeld formulation which is widely accepted in the community and can be validated by rigorous mathematical treatment [2]. The asymptotic approximation (steepest descent) of the electric field radiated by an elementary vertical electric dipole (VED) over a half-space is of interest. It is important to note that the formulation includes not only the direct and reflected waves, but also a third field component generated thanks to diffraction at the interface between the two media. This third component is naturally ignored by ray based techniques and in some cases can become predominant and improves the near-ground path loss. The appropriately simplified field expression brings out the important intervening parameters, such as the working frequency, the heights of the elementary dipoles and the interface’s electrical properties (permittivity and conductivity). In this paper, the condition for the optimal near-ground path loss is presented explicitly as a function of these three parameters. More information about the optimised path loss zone can be extracted using two distances. The first distance (ρ min ) is calculated to estimate the shortest possible distance to achieve the optimised path loss. The second distance (ρ break ) is calculated to predict the end of the advantageous zone. These three easy-to-use expressions (Figure 1.a) help to take full advantage of the near-ground link and will be presented and discussed in the final submission.

The impedance matrix of a set of distributed randomly dipoles is calculated using the Induced Electromotive Force (IEMF) technique and compared to the Numerical Electromagnetic Code (NEC). The input impedance of a surrounded dipole is assessed for any loading of the surrounding dipoles. A statistical approach is presented in order to assess the percentage of mismatch of a surrounded dipole in different random configurations.

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.

Distance estimation is the fundamental step in indoor localization. In RSS (Received Signal Strength)-based localization, the radio propagation model of a RFID (Radio Frequency IDentification) tag based on the RSSI (Received Signal Strength Indicator) measurements is used to convert the signal strength into distance. However, the propagation model for a single tag in one direction is not too accurate due to large deviations in the measured RSSI values. In this paper, an approach using a single RFID tag is presented. Performances of a single active UHF-RFID tag operating at 433 MHz are examined. Distance estimations are determined using the One-Slope Model (OSM). Improvements in distance estimations for different angles are based on an averaging algorithm which allows detecting the attenuation of the signal in a series of positions of the reader antenna. In addition, the Path Loss Exponent 'n' is also determined in different positions. Further, Experimental validations show the evolution of the Power when the distance (tag-reader) increases. Then, the Path loss contours, for measured distances, are plotted.