This paper presents a chipless radio frequency identification (RFID) sensor tag having both identification and sensing capabilities. It is based on one resonant scatterer operating as a signal ...processing antenna in the 3-7.5 GHz band. The scatterer is used to monitor a physical parameter variation, as well as to identify the remote sensor. To make a resonator sensitive to the humidity, silicon nanowires are deposited on the tag surface using a simple process. The tag needs only one conductive layer so that it can be directly printed on the product to sense and to identify. Measurements done using a bistatic radar configuration in the frequency domain validate this concept. To demonstrate the reliability of such an application, two chipless RFID sensors placed in various environments are simultaneously detected using an anticollision technique based on spectral separation.
A temperature and humidity chipless RFID sensor is presented in this paper. The tag ID as well as the two physical parameters are extracted using a traditional chipless RFID tag and interrogation ...procedure. No specific material, i.e. particularly sensitive to the quantities to be measured, is used for ease of implementation. The method is based on a model which describes precisely the evolution of the scatterer's resonance frequency as a function of temperature and humidity. The materials permittivity (impacted by these two quantities) and dilatation (impacted only by the temperature) are taken into consideration to estimate these two physical quantities independently and simultaneously using only the measurement of the resonance frequencies of two scatterers. Measurements in a controlled environment and in a real environment are achieved showing the potential of this approach for the sensor application. The sensing limitation as well as the possibility of this approach to characterize the temperature and humidity dependencies of unknown materials are also presented.
In this article, a method to characterize complex permittivity of dielectric is presented. The backscattered signal from a resonant scatterer placed in contact with the dielectric is used to estimate ...the dielectric properties. The proposed method was tested in simulation and validated in practice using different dielectric samples and different dielectric thicknesses. This method is wireless, nondestructive, with no restriction on the sample thickness and is done using a vector network analyzer (VNA) and an antenna. Discussions on the geometry of the resonator as well as the calibration step is proposed to improve the sensing capability of the approach. Monte-Carlo (MC) simulation has been performed to define a confidence interval for the values extracted with the proposed approach in the range 1-3.5 for permittivity and 0-0.2 for <inline-formula> <tex-math notation="LaTeX">\tan\delta</tex-math> </inline-formula> with an SNR of 20 dB. For example, a permittivity <inline-formula> <tex-math notation="LaTeX">\varepsilon_r = 3.54 \pm 0.06</tex-math> </inline-formula> and <inline-formula> <tex-math notation="LaTeX">\tan\delta = 0.0024 \pm 0.003</tex-math> </inline-formula> has been measured for Rogers RO4003C and <inline-formula> <tex-math notation="LaTeX">\varepsilon_r = 2.31 \pm0.05</tex-math> </inline-formula> and <inline-formula> <tex-math notation="LaTeX">\tan\delta = 0.004 \pm 0.002</tex-math> </inline-formula> for Duroid RT5880 with different thicknesses. It is also shown in simulation that the approach is compatible with materials having loss tangents up to 0.5, and real permittivity up to 10.
In this article, a novel method to improve the readability of chipless tags is presented. When the EM wave falls upon the tag's surface at normal incidence or with a known incidence, the proposed ...approach permits to obtain a higher signal-to-noise ratio (SNR) of resonators whose orientation with respect to the normal to the plane in which the tag is positioned is unknown and, thus, to increase the reading distance of the tag. It introduces a technique based on the detection of this tag orientation in relation to the antennas; a projection of the signals will allow correcting this misalignment in order to always be able to decode the tag identifier on a signal that corresponds to an ideal alignment between the tag and the antennas. With this principle, it is also possible to separate the resonance mode of the resonator that is connected to the identifier from other parasitic resonance modes that may appear due to a possible misalignment between the tag and the antenna. This principle is applied to loop resonators commonly used in chipless radio frequency identification (RFID), which can present strong parasitic modes of resonance. Also, this method makes the reading orientation invariant, allowing to read the resonator whatever its orientation with respect to the normal to the plane in which the tag is positioned. Likewise, the proposed method can be also used to sense this resonator orientation. This method requires a dual-polarization antenna and a two-port vector network analyzer (VNA). Results are validated in simulation and with real-environment measurements for a single resonator and multiple resonators, as it is classically used in chipless RFID technology. Measurements in a harsh environment, as well as comparisons with classical techniques, such as time gating (TG), are presented. A study on the improvement of the read range is achieved to highlight the potential of the proposed technique. A reading distance of more than 80 cm was, thus, obtained, which represents 20 cm more than with the classic use of a postprocessor based on time gating. Finally, the principle of the measurement is generalized by applying it to a tag with a ground plane and considering that the antenna is not necessarily placed in normal incidence with respect to the plane of the tag.
This article presents an analytical model of the radiation pattern of a loop resonator, which is frequently used as chipless radio-frequency iDentification (RFID) tags. The radiation pattern of this ...resonator can be used in practice as a sensor to determine the orientation between the tag and the antenna. Contrary to already implemented chipless RFID angle sensors, the one introduced here allows to extract rotation of the tag or the antenna position in 3-D using a novel approach based on the resonator radiation pattern. An analytical model is developed to measure the tag orientation determining both the inclination and azimuthal angle of the tag in a spherical coordinates system for both monostatic and bistatic antenna configurations. Uncertainties are studied with Monte Carlo simulations. Simulations and measurements are performed to validate the orientation extraction and evaluate the performance of the proposed solution. We show that the accuracy of this totally passive and wireless sensor is always below 5° in the measurable range with a maximum error lower than 3° for the monostatic case.
In this communication, a novel method to characterize the thermal dilatation of metals using a contactless measurement of the frequency-dependent reflection coefficient of a resonator is introduced. ...This wireless technique allows extracting the thermal expansion coefficient of the material without the need of any calibration. Two antennas, a VNA, and a scatterer fabricated with the under-test material are required. All the measurements have been achieved using a climatic chamber with absorbers to control the scatterer's temperature. The measured values for thermal expansion coefficients are in good agreement with the values provided by the manufacturer which is confirmed by a sensibility study.
This letter demonstrates the possibility of combining advantages of barcode and radio-frequency identification (RFID) technologies on the same smart label. In this letter, several UHF RFID tag ...designs based on barcodes of different standards and sizes are realized and measured using a professional RFID measurement system. Measurements of all realized prototypes are in good agreement with simulations. Interesting results are obtained with a maximum RFID read range reaching around 12 m while keeping the prototypes readability as a standard barcode. Another tag configuration which avoids soldering the IC to the structure and based on the coupling of a near-field RFID tag to the barcode is also presented, showing a read range of more than 7 m.
Thermal modeling of different transmission lines (TLs) based on resonant scatterers is presented. The coplanar strip (CPS) and microstrip (MS) TLs are used to model resonators and to introduce the ...thermal dependence. A reflectometry approach is employed to validate the model by detecting the scatterers' resonance frequency and comparing it with analytical expressions. The observable shift in the resonance frequency of the scatterers with temperature variations is due to the thermal expansion of metals and temperature dependence of the substrate permittivity. Since all the measurements are done remotely with no direct line of sight, it is shown how such a reflectometry approach can be used for remote temperature sensing using a passive label composed of resonators. Unlike previous works in this domain where the thermal dependence is considered empirically, the introduced model is used to take into account all thermal effects affecting the resonant scatterers allowing to link rigorously the variations of the measured resonance frequency with the temperature without any lookup table. Temperature sensing using very simple TLs based on resonant scatterers was demonstrated in a real environment. A temperature error of less than 3 °C is obtained. Once the temperature has been determined, it is possible to go back to the TL parameters, such as the effective permittivity and the physical length.
In this paper, a design methodology for miniaturized cavity filters in a slow wave substrate-integrated waveguide technology is presented. It is applied in the context of ladder coupling scheme with ...a slow wave effect produced by a periodic arrangement of blind via holes. By taking into account the intrinsic periodicity of the structure during the synthesis, this paper aims at achieving a better filter response in terms of bandwidth and return loss, as well as providing a systematic approach for the via holes arrangement. In addition, a segmentation technique combined with the use of polynomial fittings is introduced to provide a fast and accurate design. As an illustration, a bandpass filter of 1-GHz bandwidth centered at 11 GHz is designed, fabricated, and measured. A good agreement between simulations and measurements is obtained.
A passive harmonic tag for buried assets localization is presented for utility localization. The tag design is based on a dual-polarized patch antenna at Ultra High Frequency (UHF) band. One of its ...feeders is connected to a frequency doubler based on a Schottky diode that generates the second harmonic, which is transmitted using a linear-polarized patch tuned at this frequency. The power received at the other feeder of the dual-polarized antenna is harvested by an RF to DC converter based on a five-stage voltage multiplier whose energy is used to bias a low-power quartz oscillator that modulates the output of the doubler. The different parts of the system are presented, and the theoretical read range is estimated as a function of the soil composition and the water content. A low-cost reader based on a software defined radio is also presented. Finally, experiments with a prototype of the tag are performed for different soil conditions.
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