Ultra High Frequency Radio Frequency Identification Research Articles

An optically transparent circularly polarized ultrahigh‐frequency radio frequency identification reader antenna

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 × 100 mm2 is designed for ultrahigh-frequency RFID reader applications.

Automating inventorying of blood stations: A system based on ultrahigh-frequency radio-frequency identification (UHF RFID) technology.

Inventorying blood products is an essential process in blood station management. Traditional methods need to integrate barcodes with refrigerators, which suffer from low time efficiency, high error rate and high labour cost. Several methods have been proposed to automate this process in blood stations. However, none of them is ideal enough. In this paper, we analyse the difficulties of automation in blood inventory, and propose an automated blood inventory system based on UHF RFID technology. Comparisons over our method with manual inventory and handheld RFID inventory are conducted. The result shows that our method is nearly 10 times higher than manual inventory in time efficiency while increases the accuracy to 100%.

Passive wireless strain and crack sensing using a RFID-based patch antenna

As an important parameter of structural health monitoring, strain can be an important indicator for stress concentration and crack development. And stress/crack can effectively evaluate the health status of the structure. Micro-strip antenna strain sensing technology, as a passive wireless detection technology, is of great significance to the health monitoring of high-end equipment bearing structures. In this work, the UHF (Ultra High Frequency) RFID (Radio Frequency Identification) technology is combined with the micro-strip antenna technology. And the micro-strip antenna is used as the tag antenna to receive the energy emitted by the RFID reader and activate the tag chip of the RFID. Then the signal modulation technology is used to eliminate the noise interference in the environment, and the resonant frequency of the antenna changes with the strain/crack information is returned to the reader to realize the passive wireless strain and crack detection. Through the experiment, it proves that under different strain/crack states, the resonant frequency of the RFID-based antenna sensor decreases with the increase of strain or the increase of the depth of the crack.

UHF RFID tag localization using pattern reconfigurable reader antenna.

Passive ultra high frequency (UHF) radio frequency identification (RFID) tags have the potential to find ubiquitous use in indoor object tracking, localization, and contact tracing. We propose a machine learning-based method for RFID indoor localization using a pattern reconfigurable UHF RFID reader antenna array. The received signal strength indicator (RSSI) values (from 10,000 tags) recorded at the reader antenna units are used as features to evaluate the machine learning models with a train-test split of 75%-25%. The training and testing data is generated by a wireless ray tracing simulator. Five machine learning models: random forest regressor, decision tree regressor, Nu support vector regressor, nearest regressor, and kernel ridge regressor are compared. Random forest regressor has the lowest localization error both in terms of average Euclidean distance (AED) and root-mean-square error (RMSE). For random forest regressor, localization error results show that 90% of the tags are within 1 meter of their true position, and 67% are within 50 cm of their true position based on Euclidean distance.

Efficient Modeling of On-Body Passive UHF RFID Systems in the Radiative Near-Field

A novel method is presented to accurately determine the operational range of an on-body, passive ultrahigh-frequency (UHF) radio frequency identification (RFID) system operating in the radiative near field, based on its far-field radiation patterns. To this end, an efficient algorithm based on 3-D multipole expansion of the electromagnetic fields is formulated. By combining the new operator with the simulated or measured stand-alone far-field radiation patterns of the on-body RFID system, a comprehensive and accurate range determination is obtained. Compared with commercial software tools and measurements, we prove the accuracy and improved speed of the novel technique.

CuCl2-doped graphene-based screen printing conductive inks

The preparation of graphene-based conductive inks and their application in the field of flexible electronics have been extensively studied. However, improving the conductivity of the printed patterns always induces the neglect of the rheological properties of the graphene-based conductive inks or the mechanical properties of the as-printed patterns. In this study, the p-type doping of graphene with CuCl2 as the dopant is realized through liquid phase reaction, and the doped graphene powders are used to prepare the graphene-based conductive inks with a conductivity of 3.13 × 104 S m−1. Subsequently, to simplify the preparation of inks, CuCl2 is directly added into the graphene-based conductive inks, achieving the p-type doped graphene ink with the conductivity of 3.64 × 104 S m−1. The read range of ultrahigh-frequency radio frequency identification antenna and the temperature of the flexible electrothermal film printed with the CuCl2-doped graphene-based conductive inks can reach 7.15 m and 200°C, respectively when the equivalent isotropically radiated power is equal to 4 W and the input power density is 0.94 W cm−2. Moreover, good rheological properties of the conductive inks and high mechanical properties of the printed patterns are also obtained.

High-Gain Circularly-Polarized Square Patch UHF RFID Reader Antenna Design for Smart Factory Applications

In this paper, a UHF (Ultra High Frequency) RFID (Radio-frequency identification) circular polarization reader antenna is presented. The proposed antenna is a low cost, easy to manufacture UHF RFID reader antenna in the European UHF RFID band. The proposed antenna design employs an air-substrate patch antenna. The antenna size of 250x250x7mm. The proposed antenna works from 850 to 874 and 880 to 893 MHz with return loss less than -10 dB, thus covering the European UHF RFID band. The proposed antenna return loss bandwidth is 37 MHz. The gain of the designed antenna is 7.88 dBi at 867 MHz. Also, with a bandwidth of 864-870 MHz, the axial ratio (AR) is less than 3dB. This means that the antenna has circular polarization at 867 MHz. Each result has been calculated on CST Studio Suite 2020. The antenna recommended for use in smart factory applications promises a good antenna among RFID reader antennas.

Radio Frequency Identification (RFID) based wireless manufacturing systems, a review

Radio frequency identification (RFID) is one of the most promising technological innovations in order to track and trace products as well as material flow in manufacturing systems. High Frequency (HF) and Ultra High Frequency (UHF) RFID systems can track a wide range of products in the part production process via radio waves with level of accuracy and reliability. As a result, quality and transparency of data across the supply chain can be accurately obtained in order to decrease time and cost of part production. Also, process planning and part production scheduling can be modified using the advanced RFID systems in part manufacturing process. Moreover, to decrease the cost of produced parts, material handling systems in the advanced assembly lines can be analyzed and developed by using the RFID. Smart storage systems can increase efficiency in part production systems by providing accurate information from the stored raw materials and products for the production planning systems. To increase efficiency of energy consumption in production processes, energy management systems can be developed by using the RFID-sensor networks. Therefore, smart factories and intelligent manufacturing systems as industry 4.0 can be introduced by using the developed RFID systems in order to provide new generation of part production systems. In this paper, a review of RFID based wireless manufacturing systems is presented and future research works are also suggested. It has been observed that the research filed can be moved forward by reviewing and analyzing recent achievements in the published papers.

Hardware RFID Security for Preventing Far-Field Attacks

Radio frequency identification (RFID) is a widely used approach for a short-range contactless data exchange, i.e., employed in billing systems. During the last years, unauthorized access has become an issue, as it has been proven on numerous unpleasant occasions. A typical theft scheme is based on approaching a victim with a card reader. However, a straightforward adaptation of the reader’s antenna elements allows performing the attack from a distance, opening a severe security loophole. Here, we propose and demonstrate hardware-based protection capable of preventing a far-field attack of this kind. Our solution is based on an RFID chip shielding with an opaque metal. The Faraday type of the enclosure has a small aperture, which suppresses electromagnetic field leakage from the device. This property affects both up and down interrogation links, virtually making the far-field attack impossible. Activation of the card is done by holding it in hand–this way, it is made accessible to an authorized readout, which still remains wireless. The physical principle of the operation is placing a high-index dielectric structure next to a subwavelength aperture, making it electromagnetically larger and, as a result, supporting the field leakage. Our experimental prototype, validated by several different users, shows the capability to diminish far-field attacks on ultrahigh frequency (UHF) RFID tags. This hardware security solution can find usage in numerous applications, such as biometric passports, credit cards, and many others, where unauthorized access to sensitive data is highly undesirable.

Frequency Reconfigurable Smart Antenna With Integrated Electroactive Polymer for Far-Field Communication

For the first time, the ionic polymer metal composite (IPMC) actuator is integrated with a radio frequency identification (RFID) tag antenna for achieving frequency reconfiguration in the ultrahigh-frequency (UHF) band. Here, the IPMC movable flap serves as an actuator that can effectively tune the tag resonant frequency. By applying a two-layer-crenelated structure and employing a surface patterned electrode for restraining back relaxation, the deflection of the IPMC actuator can be significantly improved. The IPMC actuator can move in two directions, enabling two-degree frequency tuning. Numerical and experimental data confirm that the tip displacement of the IPMC actuator can be enhanced up to 266% with the use of the two-layer-crenelated structure. The IPMC actuator allows the resonant frequency of the tag antenna to be tuned back by as much as 35 MHz, after deviating due to placing on an unintended object. UHF RFID application is also performed using a portable commercial RFID reader. Good frequency reconfiguration and broad tuning range, along with far read distances, have been achieved with our tunable UHF RFID tag antenna.

An UHF RFID Circularly Polarized Tag Antenna With Long Read Distance for Metal Objects

In this letter,a circularly-polarized (CP) metal-tolerant tag antenna with a long reading distance (RD) is proposed for the ultra-high frequency (UHF) radio-frequency identification (RFID) systems. In order to realize CP radiation and high gain, a cross slot is etched on top patch to provide two orthogonal polarizations, whereas the meandered strip on the central copper layer is used to obtain a 90° phase difference between adjacent ports. An equivalent circuit model is established to better understand the operating mechanism and impedance characteristic. A prototype mounted on a 200 mm × 200 mm metal plate has been manufactured and measured to verify the design and shows an impedance bandwidth of 8 MHz (918–926 MHz) and axial ratio bandwidth of 1.3 MHz (921.6–922.9 MHz). Also, a maximum gain of 2 dBi at 922 MHz and a maximum RD of about 22.4 m have been demonstrated.

A Flexible and Low-Cost UHF RFID Tag Antenna for Blood Bag Traceability

A new low-profile flexible RFID tag antenna operating in the ultra-high frequency (UHF) European band (865 MHz–868 MHz) is proposed for blood bag traceability. Its structure combines inductive and capacitive parts with nested slots allowing for the achieving of conjugate impedance matching with the IC-chip. The whole electrical parameters of the environment (substrate, bag, and blood) were considered for the design of the tag antenna. A good agreement was obtained between the measurements and electromagnetic simulations for the input impedance of the tag antenna in the UHF band. A reading range close to 2.5 m was experimentally obtained. Therefore, this tag antenna could be effective and useful in future RFID systems for blood bag monitoring, thus improving patient safety in healthcare infrastructures.

UHF RFID Temperature Sensor Tag Integrated into a Textile Yarn.

This paper presents the design of an ultra high-frequency (UHF) radio frequency identification (RFID) sensor tag integrated into a textile yarn and manufactured using the E-Thread® technology. The temperature detection concept is based on the modification of the impedance matching between RFID tag’s antenna and the chip. This modification is created by the change in the resistance of a thermistor integrated within the tag system due to a temperature variation. Moreover, in order to obtain an environment independent detection, a differential approach is proposed that avoids the use of a pre-calibration phase by the use of a reference tag. Experimental characterization demonstrates the RFID sensor’s potential of detecting a temperature variation or a temperature threshold between and 70 °C through the variation of the transmitted differential activation power.

A Low-Power Passive UHF Tag With High-Precision Temperature Sensor for Human Body Application

Radio frequency identification (RFID) tags are widely used in various electronic devices due to their low cost, simple structure, and convenient data reading. This topic aims to study the key technologies of ultra-high frequency (UHF) RFID tags and high-precision temperature sensors, and how to reduce the power consumption of the temperature sensor and the overall circuits while maintaining minimal loss of performance. Combined with the biomedicine, an innovative high-precision human UHF RFID chip for body temperature monitoring is designed. In this study, a ring oscillator whose output frequency is linearly related to temperature is designed and proposed as a temperature-sensing circuit by innovatively combining auxiliary calibration technology. Then, a binary counter is used to count the pulses, and the temperature is ultimately calculated. We designed a relaxation oscillator independent of voltage and current. The various types of resistors were used to offset the temperature deviation. A current mirror array calibration circuit is used to calibrate the process angle deviation of the clock circuit with a self-calibration algorithm. This study mainly contributes to reducing power consumption and improving accuracy. The total power consumption of the RF/analog front-end and temperature sensor is 7.65 μW. The measurement error of the temperature sensor in the range of 0–60 °C is less than ±0.1%, and the accuracy of the output frequency of the clock circuit is ±2.5%.

A Novel UHF RFID Sensor Based Crack Detection Technique for Coal Mining Conveyor Belt

This paper presents the design and analysis of a novel passive Ultra High Frequency (UHF) radio frequency identification (RFID) based sensor for crack detection in coal mining conveyor belts. The proposed sensor is built on an interdigital capacitor (IDC) based resonator integrated with a commercial UHF RFID chip. The paper illustrates the theoretical sensing principles of the sensor along with its design requirements. To enable the operation of the conveyor belt sample in the UHF band, a dielectric characterization of the belt is performed. This characterization helps obtain the material parameters of the belt, such as the dielectric constant and loss tangent. A thorough analysis of the proposed sensor in terms of simulation and experiment is also exemplified in this paper. Both simulated and experimental studies cater to a robust sensor performance for detecting cracks in the conveyor belt environment. The simulated analysis illustrates the variation of different sensing parameters, including impedance, gain, and backscattered power, with respect to different crack widths, orientations, and locations. The experimental results of fabricated sensor prototypes eventually manifest the backscattered power variation of the sensor into the change of received signal strength indicator (RSSI). An extensive analysis of the experimentally obtained results demonstrates that the proposed sensor can reliably and efficiently detect the presence and growth of cracks along with their variation in widths and orientations. The validation of simulated results through experiments essentially lays the basis for adopting machine learning based crack characterization in the future.

Automatic Vehicle Access System using Ultra-High Frequency RFID

Securing and monitoring the territory have become a big challenge for everyone as the number of vehicle users have increased. The premise area must be secure with enforced entrances and exits. It should have an automated and efficient security and monitoring system. For this purpose, an automated vehicle access system with accurate and secure monitoring of vehicle entry and exit was developed with Graphical User Interface (GUI) and vehicle’s user database along with the prototype of Ultra-High Frequency RFID. The suitable configuration for the hardware prototype has also been evaluated to maximize the system’s capabilities. This system operates on frequencies from 400MHz to 950MHz and is performed at distances of 7 meters. The passive tag was attached to the various condition and sizes of the car. The result shows showed that the system was optimally performed with the speed of the vehicle up to 50 km/h, 7 m of reading range and a maximum 20% tinted windshield. The ideal angle for the reader is around 60ᵒ to 70ᵒ with 2 meters of mounting pole. For future improvement, it is suggested that the registered vehicle user data was linked with the official premise’s database and the data is saved in an off-site location (cloud storage). The GUI is also able to support more than 1 reader at a time depending on demand.

The Effects of Refilling Additional Rooting Material on Exploration Duration and Tail Damages in Rearing and Fattening Pigs

Pigs housed in commercial barns with slatted floors cannot fully perform their natural behavioral needs such as rooting or exploring. Enrichment materials can stimulate these behaviors in pigs. Here, we investigated whether exploration can be stimulated by offering additional enrichment material, i.e., chopped straw, once compared to four times daily. In two replicates each with four rearing and eight fattening pens, a total of 192 pigs with undocked tails continuously received chopped straw from a dispenser, while a stimulus to explore was given by filling the rooting area of the dispenser either once (R1) or four times (R4) daily with additional chopped straw. The dispensers were equipped with an ultra-high-frequency radio-frequency-identification (UHF-RFID) system in order to record the exploration durations of each individual pig at the dispenser. At four times throughout rearing and fattening, pigs were weighted and tail injuries and length losses were assessed. This resulted in three temporal sections within each replicate, for each of which the difference in tail length to the previous section (Δ-tail length) was calculated. Exploration durations did not change in long-term but increased from rearing throughout fattening. The refillings in which additional chopped straw was offered (R1 vs. R4) did not affect the overall exploration duration during rearing (linear mixed effects model (LME),P= 0.85) or fattening (LME,P= 0.66). However, descriptive evaluations showed that exploration durations decreased within the first 10-min sequences within the hour after refilling the rooting area with additional chopped straw in both treatments (R1 and R4). Exploration durations were affected by week, day, and hour within day during rearing (LME, all factors,P< 0.0001) and fattening (LME, all factors,P< 0.0001). Neither tail injuries nor length losses were affected by the refilling treatment (R1 vs. R4) during rearing (GLMM, bothP> 0.1) or fattening (GLMM, bothP> 0.1). Offering additional straw four times compared to once a day had no advantage in the present setting with regard to exploration duration and tail damages of pigs. However, refilling the rooting area with additional chopped straw triggered a short-term increase of exploration that decreased within 1 h, thus, exploration was more spread over the day.

Right-Angled V-Shaped Conformal Dual-Patch Antenna Array for RAIN RFID Doorway Portals

This paper presents a conformal ultra-high-frequency (UHF) radio frequency identification (RFID) reader antenna array for doorway portal applications. The dual-patch antenna is only 100 mm wide and right-angled (V-shaped) to fit the corners of a regular portal. Patches are arranged orthogonally to create horizontal and vertical-linearly polarized fields at near-zones and at far-field distances they provide slant-polarized fields. Beam steering is enabled by phase delaying the array elements to enhance the field coverage within the doorway portal. The antenna operates in the European UHF RFID band (865-868 MHz) with a 38 MHz, 10 dB impedance bandwidth. The antenna’s azimuth and elevation half-power beamwidth is 90° and 130°. The azimuth beam is tilted to 35° from the boresight where the gain is peaked at 5.5 dBi. This antenna is low-profile, low-cost and flame retardant and paintable. Inherited properties of the antenna’s substrate make the antenna non-toxic, self-extinguishing, lightweight and highly chemical resistant. The reader antenna is compatible with both RAIN and non-RAIN alliance UHF RFID readers.

Factors Affecting Self-Localization in UHF RFID Tag Networks

Accuracy of mobile objects self-localization in radio frequency identification (RFID) tag networks depends on many environmental and design factors. This paper analyzes effect of such factors on estimates of the mobile object location. As an estimator, we use the extended finite impulse response (EFIR) filter. It is shown that accuracy of self-localization in the ultra high frequency (UHF) RFID tag networks can be increased by the factor of several times if to optimize design of the tag and network environment and obtain the optimal angle of arrival and viewing angle. Many other factors are also considered.

Stretchable Textile Yarn Based on UHF RFID Helical Tag

In the context of wearable technology, several techniques have been used for the fabrication of radio frequency identification (RFID) tags such as 3D printing, inkjet printing, and even embroidery. In contrast to these methods where the tag is attached to the object by using sewing or simple sticking, the E-Thread® technology is a novel assembling method allowing for the integration of the RFID tag into a textile yarn and thus makes it embeddable into the object at the fabrication stage. The current E-Thread® yarn uses a RFID tag in which the antenna is a straight half-wave dipole that makes the solution vulnerable to mechanical strains (i.e., elongation). In this paper, we propose an alternative to the current RFID yarn solution with the use of an antenna having a helical geometry that answers to the mechanical issues and keeps quite similar electrical and radiative properties with respect to the present solution. The RFID helical tag was designed and simulated taking into consideration the constraints of the manufacturing process. The helical RFID tag was then fabricated using the E-Thread® technology and experimental characterization showed that the obtained structure exhibited good performance with 10.6 m of read range in the ultra high frequency (UHF) RFID band and 10% of tolerance in terms of elongation.