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关键词： phase localization   landslides   RFID   remote sensing   wireless sensor network   early warning  

摘要： Passive radio-frequency identification (RFID) was recently used to monitor landslide displacement at a high spatio-temporal resolution but only measured 1D displacement. This study demonstrates the tracking of 2D displacements, using an array of antennas connected to an RFID interrogator. Ten tags were deployed on a landslide for 12 months and 2D relative localization was performed using a phase-of-arrival approach. A period of landslide activity was monitored through RFID and displacements were confirmed by reference measurements. The tags showed displacements of up to 1.2 m over the monitored period. The centimeter-scale accuracy of the technique was confirmed experimentally and theoretically for horizontal localization by developing a measurement model that included antenna and tag positions, as well as multipath interference. This study confirms that 2D landslide displacement tracking with RFID is feasible at relatively low instrumental and maintenance cost.

关键词： chipless radio frequency identification   multi-parameter sensor   structural health monitoring   temperature and humidity sensing   wireless detection system  

摘要： Chipless radio frequency identification (RFID) technology has been widely used in the field of structural health monitoring (SHM), but most of the current research mainly focuses on the detection of mechanical properties and there are few studies on the multi-physical parameters (for example, temperature and humidity) in the climatic environment around the structure. Thus, it is necessary to design a small and compact sensor for multi-parameter detection. This paper proposes a multi-parameter chipless RFID sensor based on microstrip coupling, which supports 4-bit ID code and integrates two detection functions of temperature and humidity. Through linear normalization fitting, the sensitivity of the sensor is about 2.18 MHz/RH in the ambient relative humidity test and the sensitivity of the sensor is about 898.63 KHz/degrees C in the experimental test of water bath heating from 24.6 degrees C to 75 degrees C. In addition, this paper proposes an engineering application detection method, designs a lightweight dynamic spectrum detection and wireless transmission platform based on a lightweight vector network analyzer (VNA) and realizes the real-time extraction and transmission of RFID spectrum sensing data. The means are more flexible and economical than traditional experimental scenarios.

关键词： Antennas   Interference   Backscatter   Sensitivity   System-on-chip   Power demand   Circulators   Backscattering   fully depleted silicon on insulator (FD-SOI)   interference   radio frequency identification (RFID)  

摘要： This article presents the analysis, design, and characterization of a 61.25 GHz RFID interrogator. Monostatic RFID systems have to solve the challenge of the transmit (TX)-to-receive (RX) leakage, which could desensitize the interrogator. Instead of suppressing or canceling this leakage, the interference of the transmitted and incident waves is exploited to demodulate the incident signal. The structure can be inserted between the power amplifier (PA) and the antenna pad of existing transmitters. It has a lower insertion loss (IL) than other ON-chip isolation structures used in monostatic interrogators reported to date. The transceiver front-end was fabricated on a 22 nm fully depleted silicon on insulator (FD-SOI) technology, and has a simple structure, where the low-power receiver requires 0.022 mm<^>2 active area. The die was mounted on a radio frequency (RF) printed circuit board (PCB) and a general circuit board was used for baseband processing in the measurements.

关键词： RFID   Cournot competition   Decision-making timing   Misplaced inventory   Equilibrium strategies  

摘要： We investigate the effects of ordering-timing strategies on radio-frequency identification (RFID) adoption sequences and firms' profitability in a supply chain with a manufacturer and two retailers, both of whom suffer from misplaced inventory problems. The manufacturer is the Stackelberg leader, the two retailers engage in a quantity competition and simultaneously/sequentially make decisions on RFID adoption under two ordering-timing strategies. We derive the equilibrium strategies for RFID adoption and characterize each partner's optimal order quantity and profit. We show that the equilibrium strategies for RFID adoption are identical regardless of the two competing retailers' RFID adoption sequences. The retailer with a smaller misplacement rate will never adopt RFID alone. However, for the retailer with a higher misplacement rate: the more intense the competition is, the more likely he is to adopt RFID;ordering later always promotes him to adopt RFID;ordering earlier is more attractive than adopting RFID when the tagging cost is intermediate. Furthermore, as long as one or both retailers adopt RFID, ordering simultaneously can achieve Pareto improvement for both retailers. When neither retailer adopts RFID, the optimal ordering strategies depend on the misplacement rates and competition intensity.

关键词： Sensor tag   RFID   Humidity sensor   Nanomaterial  

摘要： In this study, a chipless RFID humidity sensor tag based on SnO2/G (Graphene) nanomaterial with recognition and sensing functions is proposed. Chip-less RFID sensors are usually composed of tag ID and sensing materials. In this paper, similar nano-spherical SnO2 powder was generated by hydrothermal method and doped with G to get SnO2/G mixture. For chip-free RFID tags, a microstrip coupled line resonator is proposed, which consists of a coupled line segment and three line segments of different shapes. Among them, u-shaped resonators coated with humidity sensitive materials for humidity sensing, and the other two resonators can code four different states. Through testing the sensitivity, hysteresis, repeatability and response characteristics of humidity sensor, it is proved that humidity sensitive material has excellent humidity sensing performance. At 11%-98%RH, the frequency offset is up to 257 MHz, achieving a sensitivity of 2.95MHz/%RH. HFSS simulation and experimental results verify that the proposed integration of humidity sensor and RFID technology has great application potential.

关键词： fluorine-doped tin oxide   optically transparent antennas   RFID   ultra-high frequency  

摘要： An optically transparent circularly polarized (CP) radio frequency identification (RFID) antenna is presented in this paper. The RFID antenna consists of a coplanar-fed waveguide inverted L-shaped monopole with a dual feeding structure. The CP wave with a bidirectional radiation pattern is obtained by feeding the radiator at both ends. The transparency of the antenna is obtained by using fluorine tin oxide (FTO) coated soda-lime glass substrate. The proposed antenna operates at a Universal RFID frequency (800-1100 MHz) with circular polarization. The antenna has an impedance bandwidth of 300 MHz and an overlapped 3-dB axial ratio (AR) bandwidth of 110 MHz (860-970 MHz, 12% centered at 915 MHz). It has a peak realized gain of 1.4 dBic. The antenna with the size of 100 x 100 mm(2) is designed for ultrahigh-frequency RFID reader applications.

关键词： Perceptions and pattern recognition   Breath monitoring   RFID   Text input   Augmentative and alternative   communication  

摘要： Patients with neuromuscular system disease may be systemic paralyzed and even lose the ability to speak. Patients can use breath to express intentions. But existing solutions either only allow patients to express several predefined sentences or cannot serve blind patients. We aim to develop a breath-based text input system named ExHIBit that allows paralyzed users, even paralyzed blind users, to freely express any sentences composed of letters and numbers. Based on the above motivation, we adopt binary sequences to express letters/ numbers, and then specify that the inspiratory and expiratory actions represent one bit information respectively. Breath-holding action serves as an indication of symbol value change (0 cent 1). We leverage commercial RFID devices to capture user's respiratory waveform. A novel recursive algorithm called Dual-Channel Follow-Keep-Pump (DFKP) is proposed to extract channel signals of respiratory waveform. Then we adopt the first-order differential features of channel signals to detect and identify respiratory actions. ExHIBit adaptively adjusts parameters to cope with the non-stationary changes of respiration. Experiments demonstrate that ExHIBit can obtain 95.14% recognition accuracy and an input speed of 1.86 word/minute.(c) 2022 Elsevier Inc. All rights reserved.

关键词： Radiofrequency identification   Time-frequency analysis   Signal processing   Signal to noise ratio   Resonant frequency   Backscatter   Frequency modulation   Collision avoidance   independent component analysis (ICA)   radar cross sections   radio frequency identification (RFID)   RFID tags  

摘要： A multitag detection technique is proposed for frequency-coded chipless radio frequency identification (RFID) to achieve minimum separations of tags, enhanced data capacity, and calibration-free features. Previous attempts for multitag detection include signal processing, comparisons with a database, and space-division multiple access (SDMA);nevertheless, these techniques rise to the challenges of large separations of tags, reduced capacity, and the complexity due to a phased array or beamforming technology, respectively. In contrast, the proposed technique overcomes these limitations by a new framework that integrates signal processing and SDMA. The capability is derived from the independent component analysis (ICA), which transforms mixing backscattering fields into an optimization model;by using the Newton method to maximize non-Gaussianity, the original resonances of each tag can be recovered. Furthermore, the proposed technique eliminates the procedure of calibration. An 8 bit system is designed and tested over 2.0-5.0 GHz. When two tags are separated by 0, 10, and 20 mm, ICA shows average reliability of 80.4%, 90.4%, and 91.5%, respectively. Thus, closely adjacent tags can be detected without calibration even for a high-density system. Real-world implementation issues, including four-tag detection, orientation mismatch, and a displacement of tags, are also analyzed to validate the proposed technique.

关键词： Mobile reader   Radio frequency   Reader-to-reader collision   Reader   Tag   RFID technology  

摘要： Today Radio Frequency Identification systems (RFID) are one of the most usable automated wireless identification technologies in the internet of things. Identification systems can exchange data remotely by communicating between a tag and a reader with sending radio waves. The main challenge of identification systems with radiofrequency in a dense RFID network is the collision, which occurs when readers are located in each other's interference range and start reading tags simultaneously. With these collisions happening, readers cannot read all the tags around them in the efficient time durations. In this research, using a distributed method and the channel listening technique, readers select a time interval to take the control channel by the Geometric Probability Distribution Function. Also, by measuring the signal strength from neighboring readers and sharing tag information, there will be an increase in the throughput of identification systems through radio waves while avoiding all kinds of collisions in the control channel. Extensive results show that the proposed method has better throughput and has less average waiting time.

关键词： moisture content (MC)   living tree   radio frequency identification (RFID)   machine learning   online sequential parallel extreme learning machine (OS-PELM)   non-destructive sensor  

摘要： Moisture content (MC) detection plays a vital role in the monitoring and management of living trees. Its measurement accuracy is of great significance to the progress of the forestry informatization industry. Targeting the drawbacks of high energy consumption, low practicability, and poor sustainability in the current field of living tree MC detection, this work designs and implements an ultra-high-frequency radio frequency identification (UHF RFID) sensor system based on a deep learning model, with the main goals of non-destructive testing and high-efficiency recognition. The proposed MC diagnostic system includes two passive tags which should be mounted on the trunk and one remote data processing terminal. First, the UHF reader collects information from the living trees in the forest;then, an improved online sequential parallel extreme learning machine algorithm (OS-PELM) is proposed and trained to establish a specific MC prediction model. This mechanism could self-adjust its neuron network structure according to the features of the data input. The experimental results show that, for the entire living tree dataset, the MC prediction model based on the OS-PELM algorithm can identify the MC level with a root-mean-square error (RMSE) of no more than 0.055 within a measurement range of 1.2 m. Compared with the results predicted by other algorithms, the mean absolute error (MAE) and RMSE are 0.0225 and 0.0254, respectively, which are better than the ELM and OS-ELM algorithms. Comparisons also prove that the prediction model has the advantages of high precision, strong robustness, and broad applicability. Therefore, the designed MC detection system fully meets the demand of forestry Artificial Intelligence of Things.