UHF RFID Research Articles

Erratum to “A Novel Compact CP Antenna with Wide Axial Ratio Bandwidth for Worldwide UHF RFID Handheld Reader”

Erratum to “A Novel Compact CP Antenna with Wide Axial Ratio Bandwidth for Worldwide UHF RFID Handheld Reader”

Efficient localization in warehouse logistics: a comparison of LMS approaches for 3D multilateration of passive UHF RFID tags

The Fourth Industrial Revolution, or Industry 4.0, aims at automating traditional manufacturing and industrial practices using modern smart technology. Autonomous mobile robots equipped with different sensors and employing different techniques have been proposed in the literature in the logistics and inventory warehouse management contexts. Efficient robot motion and planning depend on precise localization, mapping, and awareness of the environment. To properly localize items, recent attempts have been made employing radio frequency identification (RFID) in a 3D environment. This manuscript introduces four least mean squares methods to estimate the 3D positions of tags employing synthetic apertures and phase unwrapping. The proposed methods approach the localization problem solving a system of equations typical of multilateration methods to find the intersections of multiple hyperboloids. The novelty introduced here is the use of unwrapped phase distances to compute pseudo ranges for the multilateration problem. The use of such a technique is feasible thanks to precise mobile robot localization and custom navigation policies. All the analyzed methods are suitable for online localization due to reduced computation timings and have been tested on three different datasets. Two of them contain virtual data that has been generated by simulation, while the other one comes from an indoor experimental setup. Simulated tests show that combined antenna motions in 3D space (including Z-axis) improve the localization obtaining errors under the centimeter for 3D localization. Experimental tests obtained results as low as 13 cm of mean accuracy for 3D localization and 0.21 cm for 2D localization.

Inkjet Printing of UHF RFID Antennas Using Silver and Gold Inks

Compared with current methods, additive manufacturing processes could offer a more environment-friendly and cost-effective solution in producing long lasting RFID tags for identification and sensing applications. In this work we report the fabrication of UHF RFID antennas by inkjet printing on a flexible substrate. Silver and gold were chosen as ink materials since they are more resistant to weathering than other metals, particularly for applications that require long-term reusability. We compared the print performance of a commercial silver ink and our lab-developed gold nanoparticle (AuNP) ink on polyethylene naphthalate. The printing process for each ink is described using an adopted loop antenna design optimized for 866-868 MHz frequency range. Assembled passive and battery-assisted RFID tags using single-and double-layer sintered, printed antennas coupled with a readable UHF RFID chip showed tolerable detection distances using a commercial compact reader (with short read range specifications). Additionally, we observed a more consistent print behavior and quality, and consequently longer read ranges for the gold antennas (up to 40 cm with battery). Furthermore, the silver antennas oxidized over time resulting in decreased read ranges. Overall, our results show the viability of a printable gold RFID antenna with a tag working range that may be fit for close range non-contact reading.

3D target location based on RFID polarization phase model

The three-dimensional target position is vital to automatic driving, which can efficiently detect the geometrical shape of obstacles and achieve automatic environment recognition for both indoor and outdoor scenarios. In this paper, we propose an RFID 3D localization prototype based on the polarization phase model. To eliminate the impacts of tag angle, we leverage the polarization effect to obtain polarized phases. After that, we use polarized phase decomposition to get pure phases, i.e., the phase corresponding to the line of sight path. Hence, we can calculate the raw phases using the HMFCW algorithm. Finally, we can estimate the target’s 3D position according to unwrapped phase information. In this way, we implement a low-cost, high-precision, easy-for-deployment 3D position solution using commercial UHF RFID hardware. The experiments show that the method can obtain effective positioning results in various environments and achieve positioning accuracy with an average error of about 9 cm.

Stacked Planar Inverted-L Antenna With Enhanced Capacitance for Compact Tag Design

A compact tag antenna, which has a geometrical dimension of 31.5 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times31.5$ </tex-math></inline-formula> mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times3.2$ </tex-math></inline-formula> mm, is constructed using a stacked planar inverted-L antenna (PILA) for metal-mountable applications in the UHF radio frequency identification (RFID) passband. The new antenna is formed by inserting a shorted patch into a PILA structure to create a double-layered inverted antenna, which can be viewed as a cascade of two parallel resonant tanks. An increase in electric field intensity in the antenna structure has brought in sufficient capacitance for reducing the tag resonant frequency effectively to the useful UHF RFID passband. Due to the increase in the antenna reactance, conjugate impedance matching can be easily achieved between the antenna and the microchip. Fine-tuning schemes such as stubs and slits are also incorporated with the proposed tag antenna for adjusting the operating frequency to an exact precision. Measurements show that the proposed tag antenna can achieve a read distance of 7.25 m at an EIRP power of 4 W. The resonance of the proposed tag antenna is found to be very stable and it is insensitive to changes in the backing metal platform.

Study of Mutual Coupling of Typical Commercial UHF RFID Tags in a High-Density Environment

Study of Mutual Coupling of Typical Commercial UHF RFID Tags in a High-Density Environment

RFID Sensors for Monitoring Glazing Units Integrating Photovoltaic Modules

The paper focuses on the synthesis of semi-passive RFID transponders-sensors that are intended to integrate with active glazing units with built-in photovoltaic cells. The main purpose of the designed construction of the UHF RFID device is to provide diagnostic information in the monitoring system of a photovoltaic micro-power plant. Furthermore, the RFID sensor is aimed at being implemented at various stages of the product life cycle: production, distribution, storage, installation, common operation, service/maintenance and disposal. In the presented research work, particular attention is paid to several aspects of the RFID sensor synthesis: use of the energy, generated periodically in the PV cells, to power the monitoring device that has to act permanently; specification of the PV module parameters that have to be monitored in the diagnostic process; implementation of data acquisition and energy management models in an electrical circuit; wireless data transfer to the master unit (monitoring host), even in the absence of power supply (e.g., module damage, blackout), using a standardized communication protocol IEC 18000-63 used in the RFID technology; and the design of the antenna system taking into consideration limitations of electronic technology and the material properties of substrates and glasses used in PV modules and RFID sensors. Based on the results of the investigations, the modular structure of the RFID sensor demonstrator is proposed. Moreover, several diagnostic scenarios are analyzed in detail. On the basis of the provided considerations, it is shown that in order to find a malfunctioning component, it is enough to compare the voltages on the photovoltaic modules that are in the close vicinity.

Study on Low-Cost, Low-Voltage Multiprogrammable Nonvolatile Memory Cells for UHF Tag Chips

This paper proposes a low-voltage, low-cost multiple-time-programmable nonvolatile memory (MTP NVM) based on a standard CMOS 0.13 μm process for UHF RFID chip applications. The design of the differential structure cell using the tunneling effect reduces the read and write voltage. The read and write simulation test results show that the read and write operating voltage is 10 V, which is 30% lower than that of conventional EEPROMs. Because the UHF RFID tag chip requires higher voltage reduction, the structured memory cell is well suited for UHF RFID applications.

Investigation of UHF Signal Strength Propagation at Warehouse Management Applications Based on Drones and RFID Technology Utilization

As a part of the supply chain, inventory management includes, among other things, maintaining the storage of stock, controlling the amount of product for sale and order fulfilment. In business terms, inventory management means the right stock, at the right levels, in the right place, at the right time. In the case of large outdoor warehouses, common identification methods are lengthy and inappropriate. One way to determine inventory easily and quickly is to deploy UAV’s (unmanned aerial vehicle) for product identification purposes. In this case, however, there is a problem in determining where the goods are located. A drone moves at higher altitudes, which can lead to a situation where we will not be able to determine the exact location of the goods. This article deals with a method of determining the correct flight level suitable to distinguish the identified items located at least 2 m apart. The evaluation is performed based on an RSSI (received signal strength indicator) value. The experiment proved that even at maximum reading distance of selected passive UHF RFID tags the two objects can be distinguished.

Economic Advantages of Individual Animal Identification in Fattening Pigs

Pig farmers are exposed to strong international competition and confronted with low revenues, while production requirements are increasing. Individual electronic monitoring allows for closer observation of the fattening process, which can be useful for identifying weaknesses in the production process and carrying out more targeted cost management. Consequently, this study aimed to demonstrate a reduction in unit production costs through individual animal identification (IAI) using ultra-high-frequency radio frequency identification (UHF RFID) transponder ear tags. For data collection, day-old suckling piglets were individually marked. During fattening, these piglets (n = 224) were kept in 16 groups (n = 14 in each). Individual body weights and the feed consumption for each pen were recorded until slaughtering. These data were used to perform three hypothetical selection scenarios at nine different times, retrospectively, by selecting individual animals that deviated downwards from the mean value of live weight by 10, 15, or 20%. For each group, two different calculations were performed to highlight potential savings. High potential savings of direct costs (up to EUR 4.56) for female animals and castrates (EUR 5.44) were shown. Nevertheless, costs of individual data collection were EUR 4.06 per pig, and we found that IAI offers advantages for conventional fatteners for future fattening periods to work in an economically sustainable manner.

Setup-Independent Sensing Architecture With Multiple UHF RFID Sensor Tags

Ultra High Frequency Radio Frequency Identification (UHF RFID)-based sensing technology with antenna-integrated sensor tags offers a cost-effective solution for Internet of Things (IoT) applications. A multi-dimensional differential measurement technique for eliminating the effect of measurement setup, such as unknown mutual distance and orientation between the read/write device (RWD) and sensor tags, and line-of-sight obstruction, on acquiring information from multiple sensor tags simultaneously is proposed. The concept is based on 1) using a channel hopping mechanism to acquire multi-dimensional datasets and 2) conducting a dissimilarity analysis between offline and online datasets to extract sensor information. The differential measurement, which is activated by the channel hopping mechanism, mitigates the impact of the measurement setup, making the pattern of the multi-dimensional datasets tightly relate to the sensing state. A sensor tag for measuring the water filling level of polyvinyl chloride (PVC) pipes is designed and fabricated. Experiments show that the proposed method can accurately acquire information from three sensor tags simultaneously under different measurement setups. The performances using datasets of different dimensions are compared. Results reveal that using low-dimensional datasets can still be capable of getting accurate information from the sensor tags, implying that the acquisition time can be reduced.

Improved UHF-RFID Tag Design and Middleware Implementation for Effective Site Management and Access Control at Construction Site

Effective site management and access control are useful aspects to implement at the construction industry. In particular, monitoring personnel, construction materials, and equipment is considered predominant elements at these sites as they constitute more than half of the total project cost. Thus, to provide accurate and timely information of man/materials, UHF-RFID technology integrated with Middleware acts as a pioneering solution for real-time data monitoring. This work develops a new approach to implement the Automatic Identification and Data Capture (AIDC) solution through Middleware integrated with the UHF-RFID system. To design a UHF RFID tag, we propose a new platform tolerant Artificial Magnetic Surface (AMC) meta surface integrated tag for tracking man/material at the construction site. The novelties of the proposed tag lie in its improved radiation characteristics and stable high read range performance on different items. The designed tag was fabricated and tested experimentally in a real outdoor scenario by placing it on different items such as personnel and metal objects. At the same time, we developed UHF-RFID system integrated web application through Middleware to provide digital worksite visibility for access control and on/off-site management. Thus, the developed system will act as an automated tool to remotely fetch the information from different working zones at the construction site.

Electromagnetic Characterization of UHF-RFID Fixed Reader in Healthcare Centers Related to the Personal and Labor Health

Hospitals and healthcare centers are experiencing a remarkable implementation of new systems based on wireless communications technologies. Many of these systems provide location services and identification of materials, instrumentation and even patients, which promotes the increase of the quality and the efficiency of healthcare. A tracking system based on short-range radio frequency, UHF-RFID is evaluated. This system helps with location of orthopedic prosthesis according to the criteria and requirements of a specific hospital environment. It is characterized the influence of UHF-RFID system in the electromagnetic environment by measuring the parameters and characteristics of the emission levels. The results of the assessment are represented through 2D contour maps and simulations have been performed by means of an in-house 3D-RL algorithm. The proposed graph aims to provide a methodology of studying the electromagnetic environments and the evaluation of the safety conditions of workers, patients, and people in general. E field exposure levels due to the RFID localization system were analyzed in order to verify regulations concerning the safety of patients and the general public in the labor and healthcare fields. Localized electromagnetic field exposure at levels which may cause electromagnetic hazards in the specific healthcare environment have been found and potentially excessive exposure to EMF emitted by UHF RFID devices may apply to patients or bystanders. In all cases, insufficient electromagnetic immunity of electronic devices (including AIMD and other medical devices) should be considered and the electromagnetic hazards may be limited also by relevant preventive measures, as also shown in this paper, together with the principles of an in-situ evaluation of electromagnetic hazards near the UHF-RFID devices.

UHF RFID Tag Design Using Theory of Characteristics Modes for Platform-Tolerant and Harsh Metallic Environments

This paper presents a wideband, long-range RFID tag antenna design with platform tolerant features using characteristic mode analysis (CMA). The proposed design consists of a two-layer structure, that are separated by an air gap. The upper layer consists of T-match and dual loop-based meandered antenna optimized for achieving long read range characteristics in free space/low permittivity dielectrics. The second layer consists of multi-resonant strips printed on a grounded substrate carefully designed using CMA for producing multi-resonant modes in the required UHF RFID band. The multi-resonant strips help in achieving wide bandwidth and isolation between different environment surfaces. This tag antenna provides a wide bandwidth ranging from 900 &#x2013; 940 MHz that covers both the US UHF RFID band (902 &#x2013; 928 MHz) and the upper European UHF RFID band (915 &#x2013; 921 MHz). Moreover, this design achieved a read range of 14.7 m in free space, 14 m on a metal plate, and 13 m on wood, and glass. Furthermore, the proposed antenna was also tested in harsh metal environments such as car number plates and cargo metallic containers. Therefore, the proposed tag can be used for tagging metallic containers, wood containers, and other harsh platforms for cargo management, Asset tracking, supply chain visibility, and Internet of Things (IoT) Applications.

An On-Body UHF RFID Tag With DDRR Antenna for Healthcare Data Streaming Applications

This paper describes the development of a Direct Driven Resonant Radiator (DDRR) antenna for an ultra-low power UHF RFID tag system, integrating an accelerometer for movement tracking using a passive backscattering communications link. An outline of a system intended for healthcare applications involving wireless movement detection, such as therapeutic recovery exercises is described. The tag comprises of a UHF RFID transponder connected to a 4 cm (0.115λ) diameter, 1 mm thick (0.0028λ) skin-mounted antenna. Offbody read ranges of 3.6 m with 1 kB/s data communication are achieved. The DDRR radiation pattern is a limiting factor in movement tracking, offering only limited angles of detection, which could be improved with spatial diversity in the reader antennas.

Frequency-Scanned Monopulse Antenna for RSSI-Based Direction Finding of UHF RFID Tags

A compact printed-circuit leaky-wave antenna is designed to synthesize frequency-scanned monopulse patterns in the UHF RFID band from 902 to 928 MHz. A high-permittivity ceramic substrate is used to maximize the angular scanning range in such a narrow band. Two operating modes, i.e., narrow-field and wide-field modes, can be chosen by properly selecting the frequency channels and antenna ports. This allows to adapt to different fields of view while maximizing the maximum reading distance, as demonstrated with a fabricated prototype.

Energy-autonomous UHF RFID sensor for tire pressure monitoring system

Thanks to the miniaturization of components and therefore the significant reduction of energy needs, the design of passive smart-tag incorporating intelligent sensors is now possible. The goal of this study is to develop a tire pressure sensor for an electric bike with battery-free. Therefore, there is no need to replace periodically the battery, so as cuts off maintenance costs and extend the life time of the smart-tags. An UHF RFID reader installed on the bicycle frame and connected to the battery e-bike transmits the RF power at 868 MHz toward each tag integrated in the wheel rims.Firstly, this article presents the whole hardware architecture of a passive smart-tag which had to respond of technics constraints and the complexity to integrate 2 antennas in a small package box. Secondly, the methods to ensure an ultra-low consumption are developed. Finally, practical tests are compared with simulations, and, validations are carried out showing the compliance and the industrialization of this innovative system.

UHF RFID: Retail Store Performance

The development of UHF RFID technology has reached significant performance advancement in the last 20 years. Both tags and readers are now improved with better sensitivity levels providing a potential for achieving greater tag read ranges. However, the performances of the technology are also limited by complexity and electromagnetic (EM) properties of the environment in which the system operates. The aim of this contribution is to evaluate how well the state-of-the-art UHF RFID systems behave in an actual retail store environment rather than in a controlled anechoic setting. An extensive empirical study is performed and data for the performance analysis are collected from both a commercial reader and an USRP-based sniffer. It is shown that physical and MAC layer should be considered cooperatively in order to improve the overall system performance. Specifically, although the tag responsiveness depends on the products&#x2019; EM properties as well as the number of products and their relative position in the basket, still the appropriate reader mode of operation can ensure a reliable and stable reading process. For the item identification and localization in the smart IoT stores, the EM properties of retail products should be taken into account in the data classification.

High-Directivity and Circularly Polarized Compact Patch Antenna for UHF RFID Reader Devices

This paper presents the design, construction, and testing of a high directivity and circularly polarized small patch antenna for the RFID Base Stations (Readers) operating in the European UHF RFID band. The designed and optimized patch antenna structure has a 15cm ×15 cm × 0.6 cm compact size where the -3dB beam angle is reduced by using slotted ring embedded in the patch. The gain of the antenna at 862 MHz is 3.2 dBic with the E and H plain beam angle are 61.6º and 65.2º respectively. Finally, the designed antenna is compared to a single-layer patch antenna of the same cross-sectional dimensions as the proposed antenna structure.

A Cost-Efficient Hybrid UHF RFID and Odometry-Based Mobile Robot Self-Localization Technique With Centimeter Precision

This paper presents an indoor localization approach that determines the absolute position of a mobile robot platform with centimeter precision by fusing RFID localization results based on cost-effective, standard passive UHF RFID technology with the robot&#x2019;s odometry data. The mobile robot platform is equipped with a multistatic UHF RFID interrogation system, and several RFID tags are arbitrarily placed within the localization environment, serving as landmarks. The RFID localization concept is based on phase evaluations. To overcome the problem of ambiguous position estimations due to the 2&#x03C0;-phase ambiguity of the RFID signal phase and mitigate the linearization problem of the nonlinear system, a novel algorithm based on an iterative multihypothesis Kalman filter is introduced. A realistic simulation setup is developed to validate the proposed filter algorithm. By tracking a UHF RFID-equipped mobile robot platform in a real-world office environment, the proposed approach is also practically tested in terms of real-time capability, everyday suitability, and multipath resistance. Given that centimeter precision is only achieved in environments with weak multipath propagation, the RFID localization results are fused with odometry data provided by the robot. This effectively compensates for offset and drift in the odometry sensor, achieving a root-mean-square localization error of 2.7 cm.