Ultra High Frequency Radio Frequency Identification Research Articles

Long read range Class‐3 UHF RFID system based on harmonic backscattering

A high sensitivity Class-3 ultra high-frequency (UHF) radio-frequency identification (RFID) system based on harmonic backscattering to achieve a long read-range is presented. Harmonic backscattering is a promising solution to solve the carrier leakage issue of UHF RFID reader to improve the sensitivity. In the proposed RFID system based on harmonic backscattering, the RFID reader transmits data with the fundamental frequency carrier and receives data with its second harmonic carrier, and the RFID tag employs a rectifier to generate both DC power and the second harmonic carrier for backscattering without impedance mismatch. The first harmonic Class-3 UHF RFID system based on National Instruments software defined radio platform is proposed and implemented. The proposed semi-passive harmonic RFID tag has dBm sensitivity. Test results show that the harmonic RFID system has a dBm sensitivity with the harmonic RFID tag whose signal-to-blocker ratio is dB at 20 m communication distance.

BFVP: A Probabilistic UHF RFID Tag Localization Algorithm Using Bayesian Filter and a Variable Power RFID Model

We present Bayesian filter of variable RF transmission power (BFVP), a Bayesian filter-based algorithm and a variable power radio-frequency identification (RFID) model for localizing passive ultra high frequency (UHF) RFID tags in complex environments, such as distribution centers/warehouses and retail sales floors. It enables a commercial off-the-shelf (COTS) RFID-equipped robot to provide the precise locations of passive UHF RFID tagged items. First, the robot navigates and fully covers a target space to collect observation of RFID tags using a COTS reader at variable RF transmission power. Every observation is associated with a pose, where the robot receives the response, and the RF transmission power. When the robot collects all responses from an RFID tag, BFVP can estimate the location of the tag, hence, localizing the tagged item. We tested the performance of BFVP in a mock apparel store; it exhibits less than 0.5-m localization error in the practical retail environment with significant multipath fading. Our proposed BFVP could enable promising applications that could greatly improve the efficiency of supply chain management by providing the precise locations of RFID tagged items.

RFID Enabled Health Monitoring System for Aircraft Landing Gear

Radio frequency identification (RFID) has been used in the aviation industry to track and identify emergency equipment and other in-cabin assets on commercial aircraft for some time. Recently, the industry is looking to expand the use of RFID to more demanding parts and surfaces both inside and outside of an aircraft’s cabin, where RFID tags face much harsher conditions. The landing gear (LG) is one of the critical subsystems of an aircraft that plays an essential role in dispersing the energy of landing events and taxiing. Health monitoring of the LG has been suggested to help reduce both operational and maintenance costs, and extend the life of the LG beyond its current, fixed, designed service life. In this paper, we propose a health monitoring system using a combination of active wired sensors and passive RFID tags. We present the measurement of ultra-high frequency RFID tags on an aircraft landing gear using an aircraft-mounted fixed RFID reader. The results indicate that all major landing gear components and assemblies are shown to be identifiable by their EPC, and a 7 dB system margin has been achieved using 2 RFID reader antennas. Such a margin will tolerate degradations caused by harsh environments (e.g., low temperatures and high humidity) and enable update of information (e.g., flight count) stored on the RFID tags.

A Passive Wireless Sensor Network for Temperature Mapping Inside a Shielded Coaxial Enclosure

This contribution addresses the electromagnetic feasibility of the wireless temperature monitoring inside a coaxial cavity resembling a portion of a high-power high-frequency cyclotron auto-resonance maser for plasma heating in the new generation of DEMO TOKAMAK machines. The scenario is investigated as a potential communication channel for a ultrahigh-frequency radiofrequency identification (RFID) sensor network where cavity probes are used to both excite the coaxial cavity and to collect the temperature data scattered back by sensor antennas. By using a theoretical near-field analysis of a simplified model of the cavity and of the reader/sensor devices it is demonstrated that a two-probes architecture is suitable to interact with more than $N =$ 16 equally spaced RFID temperature sensors (having power sensitivity of −8.3 dB mW) over the surface of a 0.5 m tube by using less than 20 dB mW power emitted by the reader. The theoretical results are corroborated by experimental data with a mock-up of the cavity and realistic prototypes of miniaturized RFID radio-sensors and excitation probes.

RFID Technology for Management and Tracking: e-Health Applications.

Radio frequency identification (RFID) has become a key technology in the logistics and management industry, thanks to distinctive features such as the low cost of RFID tags, and the easiness of the RFID tags’ deployment and integration within the items to be tracked. In consequence, RFID plays a fundamental role in the so-called digital factory or 4.0 Industry, aiming to increase the level of automatization of industrial processes. In addition, RFID has also been found to be of great help in improving the tracking of patients, medicines, and medical assets in hospitals, where the digitalization of these operations improves their efficiency and safety. This contribution reviews the state-of-the-art of RFID for e-Health applications, describing the contributions to improve medical services and discussing the limitations. In particular, it has been found that a lot of effort has been put into software development, but in most of the cases a detailed study of the physical layer (that is, the characterization of the RFID signals within the area where the system is deployed) is not properly conducted. This contribution describes a basic RFID system for tracking and managing assets in hospitals, aiming to provide additional details about implementation aspects that must be considered to ensure proper functionality of the system. Although the scope of the RFID system described in this contribution is restricted to a small area of the hospital, the architecture is fully scalable to cover the needs of the different medical services in the hospital. Ultra high-frequency (UHF) RFID technology is selected over the most extended near-field communication (NFC) and high-frequency (HF) RFID technology to minimize hardware infrastructure. In particular, UHF RFID also makes the coverage/reading area conformation easier by using different kinds of antennas. Information is stored in a database, which is accessed from end-user mobile devices (tablets, smartphones) where the position and status of the assets to be tracked are displayed.

Development and characterization of xyloglucan-poly(vinyl alcohol) hydrogel membrane for Wireless Smart wound dressings

Hydrogel-based smart wound dressings that combine the traditional favourable properties of hydrogels as skin care materials with sensing functions of relevant biological parameters for the remote monitoring of wound healing are under development. In particular, lightweight, ultra-high frequency radiofrequency identification (UHF RFID) sensor are adjoined to xyloglucan-poly(vinyl alcohol) hydrogel films to battery-less monitor moisture level of the bandage in contact with the skin, as well as wireless transmit the measured data to an off-body reader. This study investigates the swelling behavior of the hydrogels in contact with simulated biological fluids, and the modification of their morphology, mechanical properties, and dielectric properties in a wide range of frequencies (100–106 Hz and 108–1011 Hz).The films absorb simulated body fluids up to approximately four times their initial weight, without losing their integrity but undergoing significant microstructural changes. We observed relevant linear increases of electric conductivity and permittivity with the swelling degree, with an abrupt change of slope that is related to the network rearrangements occurring upon swelling.

Wireless Passive Ultra High Frequency RFID Antenna Sensor for Surface Crack Monitoring and Quantitative Analysis.

An exponential increase in large-scale infrastructure facilitates the development of wireless passive sensors for permanent installation and in-service health monitoring. Due to their wireless, passive and cost-effective characteristics, ultra-high frequency (UHF) radio frequency identification (RFID) tag antenna based sensors are receiving increasing attention for structural health monitoring (SHM). This paper uses a circular patch antenna sensor with an open rectangular window for crack monitoring. The sensing mechanism is quantitatively studied in conjunction with a mode analysis, which can uncover the intrinsic principle for turning an antenna into a crack sensor. The robustness of the feature is examined when the variation of crack position associated with an aluminum sample and the antenna sensor is considered. The experimental results demonstrate a reasonable sensitivity and resolution for crack characterization.

A Grid-Shaped Microstrip Traveling Wave Antenna With Selective Differential Feeding Networks for CM-Level Position Detection Systems

In this paper, a near-field ultrahigh-frequency radio frequency identification (RFID) system, which has cm-level 2-D positioning precision, is proposed. The system consists of a grid-shaped microstrip traveling wave antenna (TWA) and four-port switched differential feeding networks. To selectively form tag-read sections, opposite directional currents (ODCs) are used. To introduce a microstrip TWA for cm-level 2-D positioning, the influence of $H_{z}$ fields in microstrip TWAs is theoretically analyzed. In addition, to utilize field reinforcement and achieve precise 2-D localization, a grid-shaped microstrip TWA with four-port selective switched differential feeding networks is proposed and investigated. The proposed antenna and feeding network were fabricated on FR-4 substrates. The simulated and measured results demonstrate that precise 2-D tag positioning is achieved using the proposed system utilizing ODC along two selected adjacent microstrip lines in the TWA.

Optimizing Directional Reader Antennas Deployment in UHF RFID Localization System by Using a MPCSO Algorithm

Network planning plays a critical role in the performance of ultra-high frequency radio-frequency identification (UHF RFID) system. Existing works mainly focus on the impact of reader antennas’ location with regard to coverage, quality of service, and cost, rather than localization accuracy. Moreover, since the link budget of stated solutions was investigated based on omnidirectional antennas, most research findings cannot be directly applied to practical directional localization scene. Hence, a novel deployment optimization approach for the directional reader antennas is proposed in this paper. By investigating the gain characteristic of patch antenna and dipole antenna, a propagation model is established in the first place. Then, we build a new network planning model for identifying the placement of a fixed number of reader antennas, which maximizes coverage and minimizes location error as well as interference. Finally, an improved chicken swarm optimization algorithm, termed as MPCSO, is developed for this problem. Simulation results show that the proposed approach achieves much better performance than other classic algorithms.

UHF RFID system for wirelessly detection of corrosion based on resonance frequency shift in forward interrogation power

A radio frequency identification (RFID) based system is developed in this paper as a novel passive wireless sensor to detect corrosion for structural health monitoring (SHM) of metallic surface through simulation, design, fabrication and experiment. Firstly, a 2D label-type antenna in a new configuration – circular three arm (CTA) element – is designed as an ultrahigh frequency (UHF) RFID sensor tag working on surface of steel samples. To improve gain and power transmission coefficient, a parasitic element has been added into the centre of CTA. The CTA antenna attached with the parasitic element – so called (CTAP) sensor – has a quality factor notably higher than similar metal mountable UHF RFID antennas that has been resulted to revelation of resonance frequency in measured forward interrogation power. A demonstration and validation system are introduced then to detect corrosion based on the shift of revealed resonance frequency in the forward interrogation power to activate the CTAP tag when placed on surface of corroded and non-corroded steel samples. Results show that the presented system could communicate with sensor tag to detect corrosion up to 2 m of read monitoring range at the UHF RFID standard bandwidth with a sensitivity around of 13 MHz.

Collaborative Reader Code Division Multiple Access in the Harmonic RFID System

Reading reliability is a critical aspect in the ultrahigh-frequency radio frequency identification (RFID) system when a large amount of tags are in the reading zone with complex multi-path interferences. The read failure incidences can be caused not only by the random tag position and orientation but also by the RF shadowing of other objects and tags, both of which can misalign the main lobes of the tag and reader antennas. To increase the system coverage and total read yield in practical indoor ambient, a possible solution is to employ multiple readers with overlapping reading zones. However, when the tags are within the reading zones of multiple readers, the conventional tag singulation protocol will suffer serious reader-to-reader collision (R2RC) unless the conflicting readers can agree on proper collaborative time or space division schemes. The uncertain delay of the time division multiple access and the lack of definitive time sequence can further affect the reading process, especially when the RFID system is employed for applications requiring real-time accessing, tracking, and sensing. In this paper, we introduce a collaborative reader code division multiple access (CDMA) protocol in the harmonic RFID system, which provides synchronous tag access for all readers within range. The tag can distinguish the downlink commands from multiple readers simultaneously and then formulate the response accordingly. The proposed reader CDMA is demonstrated in a simple experimental prototype to verify R2RC resolution and read yield improvement. The tworeader collaborative CDMA scheme achieved below 10−5 in the read failure rate when individual readers had 0.05 – 0.2 failure rates in the complex multi-path scenarios due to rich channel exploitation and anti-correlation in the failure incidences.

An Electrically Small, 16.7 m Range, ISO18000-6C UHF RFID Tag for Industrial Radiation Sources

We present an electrically small, long range passive ultra high frequency (UHF) radio frequency identification (RFID) tag suitable for mounting on the cylindrical metal enclosure of an industrial radiation source. The RFID tag antenna consists of a C-shaped loop over a ground plane coupled to the metal cylinder. The tag is 41 mm in diameter and 6.48 mm thick. From simulation, the tag antenna is found to have an input impedance of 16+j229 $\Omega$ at 912.5 MHz. This antenna is designed to match an ISO18000-6C UHF RFID chip having a read sensitivity of −18 dBm. The simulated realized gain of the proposed antenna is −0.3 dBi. Read range measurements are presented for different orientations and angular positions in three different scenarios. When mounted to the metal cylinder and read by an RFID reader with an EIRP of +40.5 dBm, the measured maximum read range of the proposed tag is 16.7 m in its most favorable orientation.

Functional screen printed radio frequency identification tags on flexible substrates, facilitating low-cost and integrated point-of-care diagnostics

This work explores the practical functionality of ultra-high frequency (UHF) radio frequency identification (RFID) tags screen printed onto various low-cost, flexible substrates. The need for integrated and automated low-cost point-of-care diagnostic solutions has driven the development of automated sensing and connectivity for implementation with these devices. This work explores wireless communication for paper-based point-of-care diagnostic solutions through screen printing of UHF RFID tags onto various low-cost and flexible substrates. Manual screen printing and assembly of RFID sensor integrated circuit packages and UHF RFID dipole antennas onto various substrates was performed and the practical functionality of these tags was assessed. Print quality including parameters such as resistance, roughness and print thickness are reported to illustrate the effect of the substrate on the printed result. Practical read range measurements are presented for the various tags in passive and active modes, as well as with a load connected, for different tag orientations. Results showed that the tags are adequate for clinical requirements with read ranges of at least 75 mm achieved in passive mode across the different substrates. Our results indicate that a variety of low-cost substrates can be utilized as different packaging and label options for paper-based diagnostic tests. This work presents the feasibility of implementing such devices towards low-cost, integrated point-of-care diagnostics, using straightforward fabrication techniques and realistic testing environments to illustrate the possibilities.

Novel Miniaturized Folded Line Antenna for Passive UHF RFID Tags

RFID (Radio Frequency IDentification) in UHF (Ultra High Frequency) has received considerable attention due to the different advantages offered in various fields. The tags in this technology must be attached to small objects. Therefore, the antennas size needs to be miniaturized without significant degradation. In this paper, a novel miniaturized tag antenna for UHF RFID applications is presented. The miniaturized antenna is composed of a folded line and an inductively coupled feeding loop: the antenna line is folded to reduce the antenna size, and the inductively coupled loop is used to match the antenna impedance to the chip to maximize power transfer. The miniaturized antenna is designed to operate in the USA band at around 915 MHz, and printed on a polyester substrate with a thickness of 50 µm. The performances of the proposed antenna regarding impedance, reading distance, return loss and antenna gain are evaluated using a 3D electromagnetic simulators HFSS (High Frequency Structure Simulator) and CST-MWS (Computer Simulation Technology-MicroWaves Studio) and are compared to those achieved by the conventional dipole antenna with an inductively coupled loop.

Printed UHF RFID Reader Antennas for Potential Retail Applications

Automation of retail industry is calling for the low cost solution due to its sheer size and varied needs. Printed electronics offers a great potential in addressing the needs in point-of-sales, inventory management and self-service, in particular the radio frequency identification (RFID) systems consisting of the printed components. Screen printed Ultra high frequency (UHF) RFID reader antennas have been investigated in this work for their application potentials in retails for achieving easy-implementation and low cost. The results obtained clearly demonstrated that the screen printed UHF RFID reader antennas are closely matching the performance of their circularly polarized patch antenna counterparts fabricated using the conventional chemical etching method in most critical specifications. The screen printed antennas have been explored for the monitoring of items on metal shelves targeting potential inventory management and point-of-sales applications. It has been found that all tagged items can be identified using a home developed UHF RFID system consisting of the printed antennas. The findings pave the way for the use of low cost printed antennas in the potential retail automation applications.

Multiple‐port reader antenna with three modes for UHF RFID applications

A multiple-port reader antenna for ultra-high frequency (UHF) radio-frequency identification (RFID) near-field and far-field applications which has three modes is proposed and studied. Three fed-ports are designed into the structure, which provide different radiation properties. Specially, far-field radiation for two orthogonal polarisations and near-field operation based on magnetic field coupling can be modified by feeding different corresponding port. The RFID reader antenna can work at three different operations within 820–880 MHz, including European UHF (865–868 MHz) and Chinese UHF (840–845 MHz) bands. Design details, simulation, and measured results are also presented.

Multiobjective Optimization Design for Electrically Large Coverage: Fragment-Type Near-Field\/Far-Field UHF RFID Reader Antenna Design

The design of an ultrahigh-frequency (UHF) radio-frequency identification (RFID) reader antenna covering an electrically large near-field area is challenging for near-field UHF RFID applications. In such a design, magnetic field distribution on a large coverage area is required to be as uniform as possible. For some specific UHF near-field RFID applications, given radiation pattern characteristics are expected. A fragment-type wire structure is quite suitable for these demands because uniform magnetic field distribution and given patterns could be generated through optimizing the fragmented wires in a designated electrically large area to obtain corresponding current distribution. In this article, the concept of a fragment-type structure as well as some design guidelines are reviewed and summarized. Then, two omnidirectional fragment-type wire antennas with different cell size and two directional fragment-type wire antennas are designed. Both simulation and experiment results show that there is no reading null within an electrically large near-field zone having a perimeter of four operating wavelengths at 915 MHz (i.e., 320 mm x 320 mm). The omnidirectional designs are promising in the applications of UHF near-field RFID tag detection in self-confined volumes, and the directional designs are potential in the systems of UHF near-field/far-field RFID.

Ultrahigh Radio Frequency (820-960 MHz) Identification System Affects Antioxidant Barrier in Red Blood Cell Concentrates

Background and objectives: Radio frequency identification (RFID) tags have advantages over bar codes in blood management system. Ultra-high frequency (UHF) RFID technology (820-960 MHz) in many ways has more advantages than high frequency (HF) RFID (13.56 MHz). The aim of our study was the evaluation of the effects of UHF RFID in comparison to HF RFID radiation on quality markers of RBC and on the oxidoreductive balance in RBC stored in containers labelled with RFID tags. Materials and methods: Ten RBC units were split into three components, one control unit-marked with bar code and two test units labeled with RFID tags - one operating on UHF and the second on HF radio waves. All units were stored at 2-6°C for 35 days. The test groups were exposed to radio waves continuously during storage. The quality parameters as well as concentration of malondialdehyde (MDA), and activities of superoxide dismutase, glutathione peroxidase and glutathione reductase were measured. Results: The degree of hemolysis and the concentration of K+ were statistically significant higher on 35th day of storage in RBC labelled with UHF RFID tags compare to control and HF RFID groups. On the 35th day of storage the concentration of MDA was statistically significant higher and the activities of oxidoreductive enzymes were statistically significant lower in the UHF group compare to control and HF groups. Conclusion: UHF RFID tags affect oxidoreductive balance in RBC and may lead to eryptosis. The approval of UHF RFID system for blood components needs further studies.

Fabrication and Characterization of Flexible Spray-Coated Antennas

This paper investigates the potential of using spray coating as a methodology for flexible antenna fabrication. The methodology has advantages compared with other antenna-printing techniques, such as screen-printing and gravure printing (more flexibility in design), or inkjet printing (faster production). The methodology is demonstrated using two different types of folded dipole antennas that are designed to operate in the ultra-high frequency radio-frequency identification (UHF RFID) band. Both antennas show good agreement between simulation and measurement of the spray-coated samples in terms of power reflection coefficient and gain. The two folded dipoles, with and without ground plane, show comparable performance in terms of gain, as similar antennas found in literature. The folded dipole on a ground plane is more stable near conductive surfaces and on the human body. Given these results, we conclude that spray coating is a good technique for printing small to medium sized batches of antennas.

Collision Detection and Signal Recovery for UHF RFID Systems

In this paper, we present a novel high-throughput anti-collision algorithm for passive ultrahigh-frequency (UHF) radio-frequency identification (RFID) systems. Our algorithm utilizes signal recovery techniques of collided tag signals to both recover tag communications and obtain an accurate count of all tags in the field. Passive UHF RFID systems are used for long-range passive communications for applications including supply chain management and electronic tolling. Anti-collision algorithms are used to ensure successful RFID tag communications due to the likelihood of multiple tags being in the field and attempting to communicate simultaneously. The limited on-tag functionality necessitates the use of simple anti-collision algorithms such as a dynamic frame slotted Aloha (DFSA) algorithm. With our novel collision detection and signal recovery anti-collision algorithm, the RFID reader can retrieve multiple valid communications from each collided slot in a DFSA-based anti-collision protocol, while our algorithm allocates an optimal number of slots resulting in more collided but recoverable slots and fewer empty slots. Our algorithm achieves a nearly 100% throughput improvement with an expected throughput of 0.85 compared with an expected throughput of 0.426 for a standard DFSA algorithm. The reader receiver with the proposed algorithm is implemented in a field-programmable gate array and the whole reader system is verified using the communication tests with commercial tags. According to the synthesized results in an SMIC 0.13- $\mu \text{m}$ CMOS technology, the collision detection and signal recovery module consumes about 135k GE. Note to Practitioners —Signal recovery methods are capable of extracting information from collided signals. In this paper, we introduce and analyze a signal recovery method based on the voltage histogram of the received signal. Both the original signals and the number of collided signals are recovered. The information of tags is used by our novel algorithm to increase the system throughput in DFSA-based anti-collision algorithms. The recovered signals allow our algorithm to directly obtain the tag identifier. By determining the number of collided signals, our algorithm is able to calculate an accurate estimate of the total number of tags in the reader’s field. With signal recovery and an accurate tag count, our algorithm is able to reduce the total number of slots needed to identify all tags, thereby increasing the throughput. We present a novel frame length optimization method that increases throughout by shrinking the number of slots, thereby intentionally causing collisions and reducing the total number of empty slots. In addition, we present a hardware implementation of our novel method that is suitable for integration into RFID readers. When the signal strengths of the tags in collision in the in-phase or quadrature path are not close to each other, the performance of our method is much better than that of the traditional method in which the collision signal is treated as ineffective and ignored.