Ultra High Frequency Radio Frequency Identification Research Articles

3D Printed Long-Range Cavity Structure UHF RFID Tag Antenna with Painting Conductive Ink on Convex Surface.

In this paper, we describe a long-range convex cavity-type passive ultra-high-frequency (UHF) radio frequency identification (RFID) tag to use on various metal and non-metal surfaces, for IoT sensor energy harvesting. The tag antenna is built on the 3D printed cavity structure with polylactic acid (PLA) plastic and painted with the conductive ink on the 1 mm protruding area (convex) of inner surface and the side-walls of the cavity structure to form a cavity structure. The tag is designed to operate in the UHF band (840–960 MHz). This long-range cavity tag antenna (CTA) works at both 920 MHz and 915 MHz UHF RFID frequencies. It provides a linear polarized (LP) frontal reading range of 35 m and side reading range above 15 m when mounted on either metal or non-metal objects. We describe the antenna characteristics, structure, modeling, simulation, and experimental results. A mathematical reading range also was calculated and compared with experimental data.

A Hydrogen Concentration Monitoring System With Passive Tags

This article describes the design of a hydrogen concentration monitoring system based on ultrahigh-frequency radio-frequency identification (RFID) passive tags, which adopts ISO/IEC 18000-6 Type C standard. Tag devices have been designed by employing a microcontrol unit, making the proposed solution very suitable for low-cost hydrogen concentration measurement in wireless sensor networks. Furthermore, anti-collision capability has been realized by implementing a new true random number generator based on the hydrogen concentration sensing circuit and analog-to-digital converter, without employing any additional device. The correctness of all operations of the RFID system has been experimentally verified in a multiple-tag environment, as well as the hydrogen concentration monitoring capability. Particularly, measurement on an RFID tag prototype developed for the bandwidth 920-925 MHz has revealed that when the ambient temperature is 25 °C and humidity 80%, a maximum error of 9.8% is found within a hydrogen concentration range from 0.24% to 2.4%.

Software-Defined RFID Readers: Wireless Reader Testbeds Exploiting Software-Defined Radios for Enhancements in UHF RFID Systems

In recent years, RF identification (RFID) technology in the ultrahigh-frequency (UHF) range has become increasingly important in many applications, especially in the context of both the Internet of Things (IoT) and Industry 4.0. RFID is no longer simply a matter of identification; today, it is mainly concerned with recording data from the surrounding environment. As a result, researchers are working on the integration of sensors (or even small actuators) in passive RFID transponders (tags) for a variety of different applications and also on the localization and tracking of RFID tags attached to various objects and machinery. Another key aspect in UHF RFID technologies is security, as the data transmitted may be confidential and should not be shared with third parties. For the fast verification of novel algorithms in localization and novel protocols for security, wireless testbeds allow swift verification of these designs under real-world or real-time conditions [1]. Wireless testbeds are widely used in research and require scalability, modularity, and extendibility of the hardware and software. These needs can be achieved by using software-defined radios (SDRs). In the case of UHF RFID, SDR-based RFID readers have been developed and used as wireless testbeds for enhancements in UHF RFID systems.

Advancing Ultrahigh-Frequency RFID Through Digital Signal Processing [From the Guest Editors' Desk

The articles in this special section focus on the use of digital signal processing (DSP) techniques for radio frequency identification systems (RFID).

Wideband slotted microstrip patch antenna for UHF-RFID reader

This paper is focused on the development of wideband microstrip patch antenna for Ultra High Frequency (UHF) Radio Frequency Identification (RFID) Reader application. This RFID reader can read information from tags and allow the detection of objects. Usually, the RFID Reader has narrow bandwidth and can be used in certain country only. Therefore, this proposed antenna is designed with wideband frequency, low cost and simple structure which can be used worldwide. The operating frequency range for worldwide operation is between 860 MHz to 960 MHz. The structure of the antenna is composed of a Z-shaped feedline on the upper side of FR-4 substrate and a slotted patch on the lower side. The cutting slot method has been used in this antenna design in order to improve the antenna bandwidth as well as the size of the antenna. This RFID Reader was designed and simulated using CST Microwave Studio. The overall size of the proposed UHF RFID antenna is 100 × 100 × 1.6 mm3. The proposed RFID Reader antenna has the reflection coefficient (S11) below than -10 dB and has wideband frequency from 845 MHz to 1.09 GHz in simulation result. The measured and simulated result was compared in order to analyse the performance of the designed antenna. Other antenna parameters such as radiation pattern, bandwidth and gain has also been evaluated and analysed.

Near-Field Fractal RFID Reader Antenna for Item Level Tagging

This paper proposes a novel methodology for designing near-field fractal antenna operating at European Ultra-High Frequency (UHF) for Radio Frequency Identification (RFID) systems. The principle of Oppositely Directed Current (ODC) technique is implemented to generate homogeneous magnetic field above the surface area meant for near-field RFID application. The conceptual theoretical framework of the design based on the fractal structure can be applied. The fabricated RFID reader antenna operates at 867 MHz with reflection coefficient S11 -30 dB, thus the reader antenna covering UHF RFID band range. The reading capabilities of the antenna are determined by the interrogation area of, 190mm x 243mm. It is adequate for object tracking and detection systems in pharmaceutical management and chemical industries.

A UHF RFID-Based Dynamic Object Following Method for a Mobile Robot Using Phase Difference Information

Dynamic object following is an essential ability for mobile robots in various application scenarios such as auxiliary cargo transportation, disabled assistant caring, and multirobot formation. A dynamic object following method for a mobile robot based on ultrahigh-frequency (UHF) radio frequency identification (RFID), which uses a phase difference information-based dynamic following model, is presented in this article. Through this method, a mobile robot equipped with an RFID reader can follow a dynamic target object attached with a passive RFID tag. A cost function is constructed to indicate the changes in relative distance and bearing between the target object and the following robot, allowing the real-time calculation of the translational and rotational velocities of the following robot using an algorithm base on proportional integral differential (PID)-based controllers. Compared with the existing RFID-based following methods, the proposed method can achieve a satisfactory distance and bearing following accuracy by using RFID phase difference information without any tedious and time-consuming phase drift or antenna installation calibration. Real experiments were conducted using commercial off-the-shelf (COTS) UHF RFID, and results show that the proposed method is effective and robust, the respective average distance and bearing following errors were approximately 1.65 cm and 4.94° during the robot-following tests and 4.45 cm and 6.03° during the human-following tests. The proposed method has promising applications in mobile robot following of dynamic object to provide service or assistance in large storage and manufacturing industries.

An Efficient Q‐Algorithm for RFID Tag Anticollision

In large‐scale Internet of Things (IoT) applications, tags are attached to items, and users use a radiofrequency identification (RFID) reader to quickly identify tags and obtain the corresponding item information. Since multiple tags share the same channel to communicate with the reader, when they respond simultaneously, tag collision will occur, and the reader cannot successfully obtain the information from the tag. To cope with the tag collision problem, ultrahigh frequency (UHF) RFID standard EPC G1 Gen2 specifies an anticollision protocol to identify a large number of RFID tags in an efficient way. The Q‐algorithm has attracted much more attention as the efficiency of an EPC C1 Gen2‐based RFID system can be significantly improved by only a slight adjustment to the algorithm. In this paper, we propose a novel Q‐algorithm for RFID tag identification, namely, HTEQ, which optimizes the time efficiency of an EPC C1 Gen2‐based RFID system to the utmost limit. Extensive simulations verify that our proposed HTEQ is exceptionally expeditious compared to other algorithms, which promises it to be competitive in large‐scale IoT environments.

Development and Validation of an Autonomous Radio-Frequency Identification Controlled Soaking System for Dairy Cattle

HighlightsThe high variation on how dairy cows experience heat stress opens the space for individual heat abatement options.We developed an UHF-RFID activated soaking system for dairy cattle and validated it statically and dynamically.Percentage of soaker activations was moderate when validated statically and very high when validated dynamically.Future research should validate the system using dairy cows and evaluate effects on physiology and behavior.Abstract. This study aim was to develop and validate a radio-frequency identification (RFID) controlled cattle soaking system for use in dairy cattle. The autonomous system was composed of a Raspberry Pi microcontroller, an ultra-high frequency (UHF) RFID system, a temperature-humidity sensor, and a water soaker. The system was developed and programmed to identify and tailor heat stress abatement to dairy cattle. The validation of the system was divided into static and dynamic phases. During the static phase, five UHF-RFID tags were statically placed 5 times in 11 points of interest on a ranging from 0 to 150 cm of the antenna. During the dynamic phase, 10 tags were moved 10 times each from 150 cm to the right (closer to the barn) to 150 cm to the left (further from the barn) of the center of the antenna mimicking a cow’s walking speed. During the static validation, the percentage of successful readings was moderate (MEAN±SD; 77.8±30.1%). We found that the distance from the antenna affected the percentage of successful readings (P<0.01), it was 100% up to 60 cm from the antenna and static readings were less successful from 120 cm left up to 90 cm to the right of the center of the antenna. During the dynamic validation, the percentage of successful readings was very high (96.0±7.0%). These results suggest that the autonomous soaker system seems to be able to detect cows in movement underneath the system. Future research should validate the system using live dairy cows. Keywords: Automation, Heat stress, Raspberry Pi, RFID.

UHF RFID Channel Emulation Testbed for Wireless IoT Systems.

We propose an Ultra High Frequency (UHF) Radio Frequency Identification (RFID, 902-928 MHz in the US) channel emulation testbed that is capable of simultaneously emulating unique wireless channels. The proposed system can potentially be an invaluable tool in the design and validation of RFID-based Internet of Things (IoT) sensors and systems. Emulation of ray-tracing-based wireless channels enables the evaluation of inherently difficult and complex RF scenarios, particularly in situations when in-person experimentation is not feasible or desirable (e.g., during a pandemic or in a critical care facility). Furthermore, the emulation testbed is able to generate a large amount of sensor data in a limited time period. Machine learning techniques used in wireless IoT can be greatly enhanced by a large amount of data extracted from the emulation of dynamic and challenging environments. The proposed multi-channel emulation testbed is therefore a valuable solution for experimentation on real hardware and a convenient tool for pre-clinical-trial system validation.

Crack Monitoring System for Soft Rock Mining Conveyor Belt Using UHF RFID Sensors

In general, crack monitoring of coal mining conveyor belt is carried out by simple visual inspections that are found to be inefficient due to being quite labor-intensive and for providing inaccurate health conditions of the conveyor belt. In this article, we propose a robust and low-cost passive ultrahigh-frequency (UHF)-based radio frequency identification (RFID) crack sensing system, which allows the processing and detection of the presence of crack from the sensors' data in real time. A graphical user interface (GUI) is developed and integrated into a UHF RFID commercial reader to collect and process the received signal strength indicator (RSSI) from the sensors. A theoretical model of RSSI in the presence of a crack in the conveyor belt is introduced here. The investigation on RSSI measurement has been carried out for both scenarios when the belt is static and in motion. The moving belt RSSI measurement depicts two different cases. The first case involves the interrogation of embedded sensors by using a single reader antenna, whereas multiple antennas are used for the second case. Experimental results demonstrate that the proposed monitoring system can offer highly accurate early detection of a crack having a width of as little as 0.5 mm. Moreover, the proposed GUI can enhance the system performance in processing the sensors' data using multiple reader antennas when the belt is in high motion. The experimental results have revealed promising opportunities to adapt the proposed system in a realistic scenario for monitoring the health of soft rock conveyor belts.

Shorted Patch Antenna With Multi Slots for a UHF RFID Tag Attached to a Metallic Object

This study developed a miniature tag antenna attached to a backing metal for ultrahigh-frequency radio frequency identification (RFID) applications. The impedance of this antenna can be easily controlled at the desired fixed frequency by using different mechanisms and was not considerably affected by backing metal size. This antenna comprises a radiating patch with double I-shaped slots and a ground layer shorted to a narrow inductive plate. Loading a closed slot in the center of the patch and the open slits enabled flexible frequency tuning to match the complex impedance of the microchip used. This tag antenna has a low profile of $28.02\times 25.02\times2.61$ mm3 ( $0.086\times 0.076\times 0.0079\,\,\lambda _{0}^{3}$ ), and it provides a high power transmission coefficient of 99.74%, realized gain of −2.3 dB, and a reading distance of 8.1 m when it is located at the center of a metallic plate of size $250\times250$ mm2. The operational frequency of the proposed antenna was designed to reside the frequency bands for North and South America (860–960 and 902–928 MHz, respectively). Measurements of the antenna prototype proved that the experimental results agreed with the simulated data.

A Data Augmentation-Based Method for Robust Device-Free Localization in Changing Environments of Passive Radio Frequency Identification System

Device-free localization (DFL) is playing a critical role in many applications which do not require any device attached to the target. Because of environmental changes, the fingerprint database established in the original environments is unable to remain effective when used in the changing environments. Looking at dropout as a prior-knowledge-free data augmentation operation, we propose a convolutional denoising autoencoder (DAE)-based DFL architecture AugRF. Our method combines the merits of the convolutional neural network and the DAE in which convolutional operation is beneficial to feature extraction and dropout operation is equivalent to generating augmented versions of the training data. It is noted that our method can improve the localization performance in changed environments without resampling and retraining processes. Simulations and real-world experiments verify the superiority of the proposed architecture. Our localization system can be implemented with a commercial ultrahigh-frequency radio frequency identification system. When the signal-to-noise ratio of the fingerprint data drops significantly due to environmental changes, AugRF contributes to improving localization accuracy. In addition, the time cost for one positioning meets the requirement of real-time indoor localization.

Setup-Independent UHF RFID Sensing Technique Using Multidimensional Differential Measurement

Ultrahigh frequency radio-frequency identification (UHF RFID) technology using transducer-integrated antennas provides a cost-effective option for sensing. A novel setup-independent UHF RFID sensing system that can overcome challenges caused by the measurement setup with a priori unknown mutual distance and orientation between the tag and the read/write device (RWD) is proposed. The concept is based on using off-the-shelf radio-frequency identification (RFID) chips having self-tuning capability, which maximizes power transfer coefficient between RFID chip and RFID antenna. An ON-OFF differential (OOD) measurement is implemented to provide setup-independent sensing. The OOD parameters form a 3-D vector that can support more sensing states than prior art using single-dimensional information. Power transfer efficiency (PTE) and tag sensor efficiency (TSE) are defined, where PTE is the minimal power transfer coefficient in all sensing states and TSE is the minimal pairwise Euclidean distance of the OOD parameters. The RFID antenna layout is optimized by optimizing PTE and TSE simultaneously so as to offer sensing robustness without sacrificing communication performance in all sensing states. A water filling-level sensor has been designed and evaluated. Theoretical predications are favorably compared with experimental results under different measurement setups, having different relative distances and orientations between the tag and RWD.

Novel UHF-RFID Listener Hardware Architecture and System Concept for a Mobile Robot Based MIMO SAR RFID Localization

In this paper, we introduce an ultra-high frequency radio frequency identification (UHF-RFID) mobile robot platform that is capable of performing fully autonomous inventory taking and stocktaking by providing three-dimensional (3D) product maps and thus making possible the concept of a smart warehouse. The proposed novel hardware architecture consists of an eight-channel UHF-RFID-listener for parallel signal phase recovery, including two different carrier leakage suppression circuits and a correlation decoder for each channel for the tag signal, which can handle a backscatter link frequency (BLF) deviation of up to ${\mathrm {22~\%}}$ to decode the tag data. The system also uses eight parallel channels for multiple-input multiple-output (MIMO) localization. For the system evaluation we labeled clothes stored in a warehouse with tags and generated their product map. The proposed localization algorithm is based on a synthetic aperture radar (SAR) MIMO approach that needs exact knowledge of the antenna positions and, therefore, of the driven trajectory. This position is provided by the robot, which takes advantage of a simultaneous localization and mapping (SLAM) algorithm, determining the position with ${\mathrm {1~cm}}$ accuracy while generating two-dimensional (2D) maps of the surroundings. We placed ten tags at known positions to assess the system’s performance and were able to locate these tags within a root mean square error (RMSE) of ${\mathrm {1.45~cm}}$ in 3D.

Harmonic Voltage Reflection Analysis of UHF RFID Chips

In recent years, the exploitation of the nonlinear behavior of ultrahigh-frequency (UHF) radio frequency identification (RFID) chips has gained popularity. This article presents a measurement platform for the harmonic characterization of UHF RFID chips. The measurement of the incident and reflected wave at the RFID chip terminals is performed using a digital sampling oscilloscope (DSO). A novel signal-processing methodology is presented to extract time-domain reflection coefficient equivalents from a DSO measurement at the different load modulation states. Using a simultaneous measurement of the reflection coefficient with a vector network analyzer, the obtained measurement results were validated. Furthermore, a comparison to using real-time sampling and a power spectral density analysis is presented.

Setup, Test and Validation of a UHF RFID System for Monitoring Feeding Behaviour of Dairy Cows.

Feeding behaviour can be used as an important indicator to support animal management. However, using feeding behaviour as a tool for dairy cow management an automatic sensor system is needed. Hence, the objective of this study was to setup, test and validate a ultra-high frequency (UHF) radio-frequency identification (RFID) system for measuring time dairy cows spent at the feed fence using two types of passive UHF ear tags. In a first experiment, the reading area of the system was evaluated in two antenna positions. Subsequently, the UHF RFID system was validated with video observations and compared to the measurements of chewing time of a noseband pressure sensor and of the time spent at the feed fence registered by a sensor system with real-time localisation. Differences in the reading area were detected between the two antenna positions and types of ear tag. The antenna position leading to less false positive registrations was chosen for the experiment with cows. The validation with video data showed a high average sensitivity (93.7 ± 5.6%, mean ± standard deviation), specificity (97.8 ± 1.1%), precision (93.8 ± 2.3%) and accuracy (96.9 ± 0.9%) of the UHF RFID system for measuring the time spent at the feed fence. The comparison with the noseband pressure sensor and the real-time localisation resulted in high correlations with a correlation coefficient of r = 0.95 and r = 0.93, respectively. However, substantial absolute differences between the three systems pointed out differences between direct and indirect measures of feeding behaviour in general and between the different sensors in particular. Thus, detailed considerations are necessary before interpreting automatically measured feeding data generally.

Design of a 3D-printable UHF RFID hybrid liquid antenna for biosensing applications

This paper presents a novel 3D-printable polymer-based liquid antenna for radio frequency identification (RFID) in the ultrahigh-frequency (UHF) band. Fused deposition modelling, the most widespread and inexpensive 3D printing technique, is used for printing a substrate including polypropylene (PP) and acrylonitrile butadiene styrene (ABS). An ALN-9762-WRW type RFID tag containing a meander metal antenna is modified and printed with microfluidic channels in the substrate. As an ionic liquid, a saltwater dilution is injected into the microfluidic channels designed via a computer-aided design program. A fabricated hybrid liquid antenna is tested using a 200mW UHF RFID reader with the ISO 18000-6C EPC Gen2 protocol. The sensitivity to liquid antenna radiation is measured at distances of 20–900 mm by varying saltwater dilution’s salinity and conductivity between 0 and 12000 ppm and 0-20000μS, respectively. Besides saltwater, an essential oil, peppermint oil (C62H108O7), is also used for liquid antenna. The absorption, refraction, reflection, and scattering characteristics of the polymer substratum are explored in the estimation method. The essential oil produces a buffer area in the 3D layers, which can change the polarization of the antenna. The designed and fabricated 3D-printed hybrid liquid antenna can be utilized in embedded systems suitable for chemical or biological sensing within perpetual systems such as blood or oil circuits.

Design of Nested H slot Passive UHF RFID Tag

RFID is a short distance communication system which comprises of a RFID tag, a RFID reader and a personal computer with desired software that can maintain the related information. These RFID tags can be of active or passive types. This paper focuses on design, simulation and fabrication of passive ultra-high frequency RFID tag (microchip and an antenna) which resonates at the frequency 866 MHz in the Industrial Scientific Medical Band. The nested H-slot inverted-F microstrip antenna structure is used for the design of passive RFID tag. It examines the specific tag geometry and its characteristics to optimize the PIFA antenna and in turn RFID tag’s performance.

A Flipping UHF RFID Sensor-Tag for Metallic Environment Compliant With ETSI/FCC Bands

A novel dual-band ultrahigh-frequency (UHF) radio frequency identification (RFID) sensor tag, designed to operate on metallic surfaces, is proposed. This particular UHF RFID sensor tag is capable of operating in both the main RFID frequency bands of the European Telecommunications Standards Institute (ETSI) and the Federal Communication Commission (FCC). The dual-band operation of the UHF RFID sensor tag is based on a very simple concept; by flipping the UHF RFID sensor tag on a metallic surface, it can operate either in the ETSI or FCC RFID frequency bands. The impedance and radiation characteristics of the UHF RFID sensor tag are presented with an extensive analysis of the effects of the metallic surface on the UHF RFID sensor tag. In addition, an equivalent model of the UHF RFID sensor tag, which includes the effects of the metallic surface on the sensor tag, is proposed. The UHF RFID sensor tag has a small form factor and presents a satisfying read range of around 3 m for both the operating frequency bands in a metallic environment as well as a read range of 1.4 m when operating in free space.