Ultra High Frequency Radio Frequency Identification Research Articles

Design and Simulation of a Rectangular E-Shaped Microstrip Patch Antenna for RFID based Intelligent Transportation

A low profile, rectangular E-shaped microstrip patch antenna is designed and proposed for radio-frequency identification (RFID) based intelligent transportation system (ITS) in this paper. The proposed antenna design aims to achieve high gain and low return loss at 0.96 GHz as it is suitable for ultra-high frequency (UHF) RFID tags. The proposed antenna composed of a radiating patch on one side of the dielectric substrate and the ground plane on the other side, copper is used to produce the main radiator. The simulation of the proposed antenna is performed employing the high-frequency structure simulator (HFSS). The dielectric substrate used for the suggested antenna is an FR4 substrate with dielectric constant of 4.3 and height 1.5 mm. The performance of the proposed antenna is measured in terms of gain, return loss, voltage standing wave ratio (VSWR), radiation pattern and the bandwidth. The antenna gain and the return loss of the suggested antenna at 0.96 GHz are 7.3 dB and -12.43 dB, respectively.

A Versatile Flexible UHF RFID Tag for Glass Bottle Labelling in Self-Service Stores

Low-cost and versatile radio frequency identification (RFID) tag for bottle labeling is in great demand with the rise of self-service stores. Especially, robust performance is of great importance when the tag is needed to be attached on different liquid products. This paper proposed a versatile and flexible ultra-high frequency RFID tag for liquid products with glass bottles. The tag antenna is based on a simple loop structure, which has a strong concentrated magnetic field. As opposed to conventional dipole-based RFID tags, the loop-based antenna is less affected by liquid. Simulations and measurements of the tag have been carried out in different application scenarios. Significant factors, such as installation position, liquid amount and type, bottle shape, and thickness, have been investigated to find out their influences on the proposed tag. According to the simulation and experimental verification, the performance of the tag is robust despite changes of the significant factors, and specifically, the tag antenna keeps well matched around the FCC band and the reading ranges remain 1.6–2.5 m in multiply application scenarios. This makes the proposed tag versatile and feasible for a variety of liquid products with glass bottles in self-service stores.

Low‐Profile Flexible UHF RFID Tag Design for Wristbands Applications

In this study, a low‐profile ultrahigh frequency (UHF) radio‐frequency identification (RFID) tag antenna designed for wristbands in healthcare applications is proposed. The radiator is based on the open‐slot cavity technique that is composed of a slotted patch (double‐T slots) loaded onto a flexible open cavity. The proposed slotted design can easily allow the tag’s input impedance to be tuned to the complex impedance of typical UHF RFID chips. The proposed tag antenna has a size of 86 mm × 25 mm × 1.6 mm (0.26λ0 × 0.07λ0 × 0.004λ0) at 915 MHz, and it can yield a maximum reading range of 8 m (stand alone in free‐space condition), 6.6 m (when placed on the human wrist in free‐space condition), and up to 3 m (when placed on the human wrist in a crowded condition).

A Study of Walking Speed Measurement for Elderly Health Assessment Using UltraHigh-frequency Radio-Frequency Identification Tags

A Study of Walking Speed Measurement for Elderly Health Assessment Using UltraHigh-frequency Radio-Frequency Identification Tags

Artificial intelligence in safety system

This research aims to study learning environment, and let the learning environment become smart. Swarm intelligence, cloud computing, and active Ultra-High Frequency RFID were used on it. We built friendly human-computer-interface software for users to use as pad phone. The Extensible Markup Language (XML) and C sharp language were used in this research. If the users begin to search, the kernel safety learning system automatically communicates with other RFID readers by agents, and the agents can search the closer camera for users. This study’s result has successfully implemented to Chin-Huo educational organization, and it would be helpful for the paterfamilias to hold all situations about their children at Chin-Huo educational organization. Paterfamilias can understand their children’s learning, going to Chin-Huo and leaving Chin-Huo through personal computers, or notebooks simultaneously or asynchronously by the computer-mediated communication. That will be great help in the grip of whole after-school remedial education, teaching and learning situation.

A broadband circularly polarized antenna of square-ring patch for UHF RFID reader applications

A circularly polarized, broad bandwidth, square-ring patch antenna for radio-frequency identification (RFID) is proposed. The antenna has a dimension of 100 × 100 × 22.9 mm3. By using a Wilkinson power divider and a patch-antenna structure, a measured 3-dB axial-ratio bandwidth of approximately 140 MHz (16.47%), an impedance bandwidth of 136 MHz (15.81%), and a measured peak gain of approximately 6.8 dBic are being achieved. The operating band of the proposed antenna is suitable for China (840–846 MHz), Europe (865–868 MHz) and the United States (902–928 MHz) ultra-high frequency (UHF) RFID applications.

Monitoring trough visits of growing-finishing pigs with UHF-RFID

Automatic monitoring of animal feeding behaviour in commercial farms is desirable as it is an important indicator for the well-being and health of animals. Low-frequency and high-frequency radio frequency identification (RFID) systems have been tested for the detection of feeding visits of growing-finishing pigs, but the suitability of ultra-high frequency (UHF) RFID for this application has not yet been shown. Therefore, the objective of this study was the validation of a UHF-RFID system, consisting of a reader, antennas and passive transponder ear tags, for the monitoring of visits of growing-finishing pigs at a short trough for liquid feeding. Consequently, (1) two antenna variants (free-form and patch antennas) were tested at different levels of antenna output power, (2) two methods to determine a bout criterion for the creation of trough visits from the RFID registrations were compared, and (3) a comparison of the RFID data with reference data from video observation was carried out. The analysis showed that the reading area exceeded the trough especially in the variants with high output power. Thus, the evaluation of the first and second rate of change of the total daily number and total daily duration of visits led to higher values for the bout criterion (50 s for both antenna variants) than the evaluation of the mean absolute deviation between video and RFID data (20 s for the free-form antenna and 30 s for the patch antennas). The trough visits observed were detected best with the patch antennas at 25 dBm output power and a bout criterion of 30 s with regard to average precision (61.1%), and correlation between the video data and RFID visits (R2 = 0.87 for total number and 0.80 for total duration of visits). The average sensitivity of this variant was 49.7%, specificity 99.0% and accuracy 97.9%. The highest average sensitivity (79.7%) and a good correlation between video data and RFID visits (R2 = 0.78 for total number, 0.56 for total duration of visits with a bout criterion of 50 s) were measured with the free-form antenna at 26 dBm. In conclusion, UHF-RFID can be suitable for the monitoring of trough visits of growing-finishing pigs, but the effect of ear tissue on the performance of the UHF-RFID ear tags should be reduced by further development. In addition, further research should be carried out to evaluate the potential of this technology completely for animal behaviour monitoring.

Miniaturization of UHF RFID Tag Antenna Sensors for Corrosion Characterization

Three ultra-high frequency (UHF) radio-frequency identification (RFID) tag antenna-based sensor designs for steel corrosion sensing with miniaturization are proposed in this paper. To characterize corrosion, a new antenna adopts the structure of patch antenna with a meanderline feed based on microstrip line theory. The impedance change of the meanderline feed results in detuning in the tag antenna so that this change can be captured with threshold power of the tag. Folded antenna with 3-D structure has been redesigned for miniaturization from the non-folded antenna to reduce the antenna size for spatial resolution enhancement, but the gain is reduced as well as sensitivity. A T-shape antenna is proposed to increase the gain of the miniaturized antenna and the sensitivity. Experimental studies with ThingMagic development kit on dedicated corrosion samples have been undertaken to validate the antenna designs. Resonant frequency features of the developed antenna are studied for corrosion characterization, but the bandwidth of UHF RFID limits the measurement range. Principal component analysis method is applied to evaluate different corrosion stages and reduce environmental interference.

IQ signal based RFID sensors for defect detection and characterisation

Radio frequency identification (RFID) sensor systems have unique advantages of identification, communication and sensing together. Previous researches on RFID based sensing investigate power based features, and face the challenges of low sensitivity and robustness due to environment RF field. In this paper, rather than using received signal strength indicator (RSSI), we present a method using features of transient responses from in-phase quadrature (IQ) signal to overcome the challenges of sensitivity and robustness in ultra-high frequency (UHF) RFID sensor systems. The transient responses of the IQ signal are analysed using skewness feature for different defects. The experimental results show that IQ based skewness features from IQ signal improve sensitivity and robustness for defect characterisation compared with previous RSSI and RCS methods.

Algorithm for Detection of Unwanted Tag Reads in Passive UHF RFID Systems for Static Metallic Objects

Passive Ultra High Frequency Radio Identification (UHF RFID) systems used in metal objects exhibit challenges due to generation of Foucault currents and multiple reflections, creating reading problems and detection errors. One of these problems is unwanted RFID tag reads i.e., tags unintentionally detected by the reader. The paper presents one algorithm for reduction of such unwanted tag reads using normalized read rate and range of RFID tags. The algorithm was designed using extensive data from measurements of an actual RFID system with tags located over metal objects. Results show that the algorithm detects 96% of unwanted tag reads.

A wirelessly powered RFID-based smart contact lens system

This paper presents a wireless smart contact lens system, comprising a capacitive sensor interface circuitry and a wirelessly powered radio frequency identification (RFID)-compatible system, for sensor control and data communication. To improve compliance and reduce user discomfort, the capacitive sensor was embedded on a 200-μm-thick soft contact lens using commercially available biocompatible lens material and a standard sandwich manufacturing process. The proposed lens can communicate with RFID equipment at an ultra-high frequency (UHF) RFID frequency of 920 MHz. A successful communication distance of 2 cm was achieved under 18 dBm incident radio frequency (RF) power, and a maximum distance of 4 cm was achieved under 28 dBm incident power. The uniform magnetic field distribution of the transmitting antenna enhances energy transmission and provides robust operation against shifts in relative location and misalignment of the contact lens and the glass caused by eye movement and blinking.

Influence of Temperature on the Dynamic Reading Performance of UHF RFID System: Theory and Experimentation

Abstract The radio frequency identification (RFID) system is vulnerable to a variety of factors (metal, liquid, temperature, and so on) in the practical application. In this paper, the reading distance of tags, as the evaluation criteria for the reading performance of the RFID system, is focused on to study the influence of environmental temperature on the dynamical performance of an ultra-high frequency (UHF) RFID system. An experimentation system, including temperature control system and detection platform, is devised to control temperature and measure the reading distance of the RFID tag. According to the experimental data of the tag's reading distance at different temperature, a fitting model between temperature and tag's reading distance is established. Experimental results show that the tag's reading distance decreases with the increase of temperature. Finally, the corresponding temperature compensation mechanism is deduced to get the reading distance under the same reference temperature. This paper provides an effective method for selection and evaluation of UHF RFID tags at different temperature.

Reliability and Failure Analysis of UHF RFID Passive Tags Under Thermal Storage

This paper proposes studying the effects of thermal storage on the reliability of passive ultra-high frequency radio-frequency identification tags. Two types of tags M1 and M2 from two different manufacturers are aged under two high temperatures equal to 408 K and 433 K. Tested tags are put into thermal storage oven hang fixed terms. The performances of these tags are measured after each aging phase to determine the power loss caused by high-temperature storage. Then, a mathematical approach is used to estimate for both tags from the two manufacturers the law of reliability under nominal conditions. Statistical and physical analyses of the results allow us to study and analyze the mechanisms of aging. It is observed that the failure mechanisms depend on the type of passive tags and the values of selected storage temperatures for the tests. The scale parameters of M1 tags aged at 408 K are around 280 h, whereas the scale parameters of the M2 tags aged at the same temperature are around 360 h. Cracks on the antenna are observed with the higher temperature equal to 433 K for M1 tags. However, the changes of the performance of others tags are probably caused by changes in the matching of the impedance between the antenna and the radio-frequency integrated circuit. From this study, various failure mechanisms demonstrate the necessity of determining the type of passive tags and the used temperature.

CPW-fed Circularly Polarized Slot Antenna with Small Gap and Stick-shaped Shorted Strip for UHF FRID Readers

Abstract A new circularly polarized (CP) slot antenna with a small gap and a stick-shaped shorted strip is presented. The proposed antenna has a sufficient bandwidth for ultrahigh frequency (UHF) radio-frequency identification (RFID) reader applications. The antenna structure consists of a rectangular slot with a small gap, a stick-shaped shorted strip and a 50 Ω coplanar waveguide (CPW) feedline with an asymmetrical ground plane. By using the stick -shaped shorted strip to disturb magnetic current distribution on the slot, the CP radiation can be generated. The measured results demonstrate that the proposed antenna can reach a 10 dB return loss impedance bandwidth of 14.1 % (894–1030 MHz) and a 3 dB axial ratio (AR) bandwidth of 6.4 % (910–970 MHz). The whole antenna size is 80 × 80 × 1.6 mm3.

IoT Localization for Bistatic Passive UHF RFID Systems With 3-D Radiation Pattern

Passive radio-frequency identification (RFID) systems carry critical importance for Internet of Things (IoT) applications due to their energy harvesting capabilities. RFIDbased position estimation, in particular, is expected to facilitate a wide array of location-based services for IoT applications with low-power requirements. In this paper, considering monostatic and bistatic configurations and 3-D antenna radiation pattern, we investigate the accuracy of received signal strength-based wireless localization using passive ultra high frequency RFID systems. The Cramer-Rao lower bound (CRLB) for the localization accuracy is derived, and is compared with the accuracy of maximum likelihood estimators for various RFID antenna configurations. Numerical results show that due to RFID tag/antenna sensitivity, and the directional antenna pattern, the localization accuracy can degrade at blind locations that remain outside of the RFID reader antennas' main beam patterns. In such cases optimizing elevation angle of antennas are shown to improve localization coverage, while using bistatic configuration improves localization accuracy significantly.

Experimental assessment of an RFID-based crack sensor for steel structures

The use of welded steel cover plates had been a common design practice to increase beam section capacity in regions of high moment for decades. Many steel girder bridges with cover plates are still in service. Steel girder bridges are subject to cyclic loading, which can initiate crack formation at the toe of the weld and reduce beam capacity. Thus, timely detection of fatigue cracks is of utmost importance in steel girder bridge monitoring. To date, crack monitoring methods using in-house radio frequency identification (RFID)-based sensors have been developed to complement visual inspection and provide quantitative information of damage level. Offering similar properties at a reduced cost, commercial ultra-high frequency (UHF) passive RFID tags have been identified as a more financially viable option for pervasive crack monitoring using a dense array of sensors. This paper presents a study on damage sensitivity of low-cost commercial UHF RFID tags for crack detection and monitoring on metallic structures. Using backscatter power as a parameter for damage identification, a crack sensing system has been developed for single and multiple tag configurations for increased sensing pervasiveness. The effect on backscatter power of the existence and stage of crack propagation has been successfully characterized. For further automation of crack detection, a damage index based on the variation of backscatter power has also been established. The tested commercial RFID-based crack sensor contributes to the usage of this technology on steel girder bridges.

Design of a Multipolarized RFID Reader Antenna for UHF Near-Field Applications

This paper presents our investigation into a novel ultrahigh-frequency (UHF) radio frequency identification (RFID) multipolarized reader antenna based on a pair of symmetrical meandering open-ended microstrip lines for near-field applications. The near-field and multipolarization operation is achieved by introducing a 90° phase shift between the currents flowing along the opposite side of two branches. The proposed antenna is shown to generate a uniform and strong electric field in its near-field region within a reading volume: $450~\text {mm} \times 450~\text {mm} \times 350$ mm ( $\text {width} \times \text {length} \times \text {height}$ ). The simulated and measured impedance bandwidths (−10 dB) agree very well, ranging from 825 to 965 MHz and covering the UHF RFID standard. In addition, it exhibits a low far-field gain, avoiding to misreading the tags outside the near-field region. The fabricated antenna was fully tested with multiple tag antennas that are placed in different orientations and even in a conveyor system, demonstrating a 100% reading rate of arbitrarily oriented tags within the reading zone.

Flexible and stretchable 3D printed passive UHF RFID tag

The fabrication and analysis of a flexible and stretchable 3D printed passive ultra-high frequency (UHF) radio-frequency identification (RFID) tag are presented. The tag is fabricated on a flexible 3D printed Ninjaflex substrate and the conductive part of the tag consists of stretchable silver conductive paste dispensed with direct write method. The details of the 3D printing of the substrate, the characterisation of the substrate material at the UHF band, the direct write dispensing of the tag antenna, and the simulation and wireless measurement results of the fabricated tag are outlined. Moreover, to verify the flexibility and stretchability of the tag, strain reliability results of the tag are presented. Measurement results show that initially the manufactured tag achieves a 10.6 m read range. After 100 times of harsh stretching, the read range is still 7.4 m. Overall, the performance of the tag is robust and concludes that the fabrication methodology can be used in the manufacturing of RFID tags for future identification and sensing applications.

Dual-band circularly polarized flat antenna with plano convex and concave slots for RFID readers

This article has proposed a circularly polarized dual-band antenna with unidirectional pattern operating at the bandwidth frequencies of 920–925 MHz and 2.40–2.48 GHz for radiofrequency identification (RFID) readers. The proposed antenna structure is of a radiating patch with a single feeder and two pairs of plano convex and concave slots. This work has innovated and utilized the convex and concave slotting technique to generate the circular polarization. The simulated results showed that the dual-band antenna is of circular polarization (CP) and unidirectional radiation pattern with the 3 dB axial ratio and the respective gains of 1.31 and 1.36 dBic for the experimental lower and upper bandwidth frequencies. An antenna prototype was subsequently fabricated and tests performed. The simulated and measured results are in good agreement, rendering the proposed dual-band antenna with plano convex and concave slots suitably applicable to the ultrahigh frequency and microwave RFID readers.

Novel approach to determine the influence of pig and cattle ears on the performance of passive UHF-RFID ear tags

The potential of passive ultra-high frequency radio frequency identification (UHF-RFID) as an electronic identification technology for precision livestock farming applications has been evaluated in different projects. Despite very promising advantages, such as a high read range and simultaneous identification of animals, the application of UHF transponders in ear tags still struggles with the strong influence that body tissue in the vicinity of the transponders has on the reading performance of the system. A detailed and precise investigation of the influence of ears on the transponder ear tags to support transponder development is hardly possible in on-farm tests with animals. Thus, the aim of this study was to develop an approach to measure the influence of pig and cattle ears on the received signal strength indicator (RSSI) and read range of UHF transponder ear tags on a test bench. In a second step, replacement of cattle and pig ears in the experiments with tissue models was tested to enhance the repeatability and comparability of results. Three sets of tests were performed with three different types of UHF transponders (1) to compare the influence on the read range and RSSI of the transponders at the front and back of pig and cattle ears, (2) to determine the repeatability of measurements with ears, and (3) to compare the influence of pig ears with that of two tissue models. Results showed significant differences between the front and back side of the ears for pig ears with better results at the back. The results for cattle ears were heterogeneous. The repeatability of measurements was low in all variants (front and back of pig and cattle ears) with repeatability coefficients of up to 10dBm (RSSI) and 217cm (read range). The tests generally demonstrated the strong and highly variable influence of ear tissue on the read range and RSSI of the transponders. Nevertheless, the results indicated that targeted detuning of UHF transponders can lower the influence of ear tissue on the reading performance, which is promising for the use of UHF-RFID in livestock farming. The method presented could be used in an optimised manner in the future to perform comprehensive tests and comparisons of different types of UHF transponder ear tags.