Passive Ultra High Frequency Radio Frequency Identification Research Articles

High Gain Passive UHF RFID Reader Antenna Using Novel FSS for Longer Read Range

Frequency Selective Surface (FSS) is widely used to enhance the gain of antenna & reduces Electromagnetic Interference (EMI). In this work, a novel Frequency Selective Surface (FSS) is designed, analyzed, and fabricated along with passive Radio Frequency Identification (RFID) reader antenna operating at global Ultra-High Frequency (UHF) for wireless RFID applications. The antenna & FSS sheet is fabricated on less costly FR4 substrate with resonant bandwidth of 860–960 MHz. The Fabry–Perot arrangement of FSS sheet with antenna increases the gain & directivity without modifying the antenna profile or increasing radiation patch size. The maximum measured gain is 9.8 dB & 7.2 dB with the Reflection coefficient (S11) of −35 dB & −15 dB at 910 MHz & 950 MHz respectively. The proposed antenna of dimension 40 mm by 40 mm is fabricated & tested for further experimental validation with measured read range longer than 8 m. The novelty in proposed work is integration of FSS with passive UHF RFID technology which can be effectively used in wireless RFID applications for improved read range, higher gain, lower power consumption & better immunity within the resonating band. The proposed antenna effectively isolates out-of-band frequencies from in-band frequencies over a required bandwidth reducing Electromagnetic Interference (EMI) for UHF RFID applications.

A Novel RFID Localization Approach to Smart Self-Service Borrowing and Returning System

The misreading problem of a passive ultra-high-frequency (UHF) radio frequency identification (RFID) tag is a frequent problem arising in the field of librarianship. Unfortunately, existing solutions are something inefficient, e.g., extra resource requirement, inaccuracy, and empiricism. To this end, under comprehensive analysis on the passive UHF RFID application in the librarianship scenario, a novel and judicious approach based on RFID localization is proposed to address such a misreading problem. Extensive simulation results show that the proposed approach can outperform the existing ones and can be an attractive candidate in practice.

Timing: Tag Interference Modeling for RFID Localization in Dense Deployment

Due to low cost and low complexity, passive ultrahigh-frequency radio-frequency identification (UHF RFID) is gaining popularity in indoor localization. According to current RFID channel models, multipath propagation and noise are two significant factors that affect the accuracy of measured RF signals. To minimize the impacts of measurement errors on localization, scene analysis algorithms are proposed and got lots of attention in recent years. These algorithms make use of reference tags as similarity markers in neighboring locations to improve localization accuracy. However, densely deployed tags induce a new challenge, antenna interference, leading to the poor signal similarity between nearby tags. Nonetheless, there are no refined channel models for explaining the effect of spacing distances between tags on RF signal fluctuations, thus the choice of spacing distances becomes an outstanding issue for scene analysis localization algorithms. In this article, we propose Timing, the Tag Interference ModelING, for analyzing the relationship between signal fluctuations and spacing distances. Unlike inductive coupling in the near field, as the tags are all located at the far field of interacted antenna, we introduce microwave transmission line theory for channel model analysis. The experimental results verify that Timing is well suited to authentic situations. Additionally, we examine the performance of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> -nearest neighbor ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> -NN) algorithm under various spacing distances. The findings demonstrate that the spacing distance identified by Timing as a stable point achieves better accuracy with scene analysis algorithms. Therefore, Timing could be used as a critical foundation for the choice of spacing distances in future tag deployment applications.

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.

Performance Evaluation of Passive Tag to Tag Communications

In the context of the UHF (Ultra High Frequency) passive RFID (Radio Frequency Identification) technology, recent works have proposed a new paradigm demonstrating the possibility to perform short distance tag to tag (T2T) communications. This paper presents a study that focuses on the performance evaluation of T2T systems. Without loss of generality as to the methodology followed, dipole antennas are considered here (assumed ideal in the theoretical part, then printed for the rest of the study). The results obtained show that the modulation depth, which can be considered as an evaluation metric for the T2T systems, is strongly impacted by three main parameters: the switching impedances (here chosen as short-circuit and open-circuit); the geometrical configuration constituted by the two tag antennas forming the T2T system; and also, the position of the external source on which the backscatter communication relies. As the modulation depth is very sensitive to these three parameters, which are more or less directly related, it is very difficult to predict the communication quality for a given configuration. For example, when the two tags are in parallel and the source is symmetrically positioned, the modulation depth shows a decreasing trend by oscillating when the distance between the tags increases from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.1~\lambda $ </tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1~\lambda $ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> being the wavelength): with values going from 70% to less than 5%. As a consequence, from a very complete set of scenarios considered, the presented study helps to illustrate and explain the interactions of these parameters and their impact on the modulation depth. And at the same time, the paper provides guidelines for defining the specifications of such a system based on quantified results. The set is completed by introducing the BER (Bit Error Rate) as an evaluation metric by considering then a more complete T2T system (for instance listener tag including a non-coherent envelope detector).

Radiation Beam Pattern Control of UHF RFID Tag Antenna Design for Automotive License Plates

This paper presents a design of a radio frequency identification (RFID) tag antenna in the ultra-high-frequency (UHF) range, which is applicable to a vehicular license plate attached to a vehicle bumper. The main goals are to first improve the identification ratio by controlling the radiation beam pattern and, second, to control the beam direction. Since every vehicle has a license plate, the available plate structure is used to design the antenna. The shape of the tag is rectangular and has a dimension of 525 mm × 116 mm, which is smaller than the typical size of standard plates, 540 mm × 120 mm, used in Europe and Korea. The fabricated tag antenna, the license plate, and the vehicular bumper are fixed by volt and nut. For vehicle tracking and identification, RFID readers are deployed on the road side. For efficient identification, a long distance passive UHF RFID license plate with a patch antenna is proposed to provide not only line-of-sight identification but also left and right beams. Unlike the general UHF tag antennas, in this paper, the patch antenna is designed to attach to the metal part of the car, the license plate holder. The beam patterns of the RFID tag antenna can be controlled by the patch antenna parameter values. The simulation result demonstrates that the proposed UHF RFID tag antenna has a beam radiation pattern as required at 920 MHz. In addition, the estimated read range of the proposed plate meets the requirement of RFID systems.

Experimental Results and Performance Analysis of a 1 × 2 × 1 UHF MIMO Passive RFID System.

Ultra-high frequency (UHF) multiple input multiple output (MIMO) passive radio frequency identification (RFID) systems have attracted the attention of many researchers in the last few years. The system modeling and theoretical performance analysis of these systems have been well investigated and revealed in many studies, yet the system prototype and the corresponding experimental results are scarce. In this study, measurements of a 1 × 2 × 1 UHF passive RFID system, including a MIMO UHF passive RFID tag prototype and its corresponding software-defined radio-based reader, taken in a microwave anechoic chamber, are presented. The experimental results are compared with theoretical values and computer simulations. The overall results demonstrate the consistency and the feasibility of UHF MIMO passive RFID systems.

Long-Range UHF RFID Tag for Automotive License Plate.

In this paper, various locations of an Ultra High Frequency (UHF) Radio Frequency Identification (RFID) tag on automotive license plates have been considered based on the radiation pattern of the tag antenna. A small, 130 × 50 mm, passive loop antenna type UHF RFID tag for an automotive license plate was simulated with an EM simulation CST program. It was designed to have a larger back-lobe radiation pattern since the front side of the tag faces the back side of the plate holder to protect the tag antenna from bugs and dust when the automobile runs. The tag was attached to the side of a license plate holder with a dimension of 520 × 110 mm, the typical size of the standard license plate. The reflection coefficient of the tag antenna is −21 dB at 920 MHz, and the gain of the tag antenna is 6.29 dBi at the back-lobe. The reading range of the tag antenna with the plate holder, which was measured in an open field, is about 10.3 m, and the reading range of the tag installed on the bumper from the front of the vehicle is 9.4 m. The tag antenna is small enough to apply to a real automobile, and it is applicable because it uses the back-lobe pattern, so it does not require an extra device for protection from damage.

Passive UHF RFID tags made with graphene assembly film-based antennas

Ultra-high frequency (UHF) radio frequency identification (RFID) tags with an antenna made of a highly flexible graphene assembly film (GAF) is presented. The superb electrical conductivity (∼1.6 × 106 S m−1) of the GAF results in the tag to reach reading range of ∼12 m, which is comparable to that of the commercially available metallic counterparts. The performance of the GAF-based RFID tags under mechanical bending and stretching is experimentally evaluated, which demonstrates excellent mechanical stability of the GAF tag than that of metallic tags. Additionally, substrate stability tests are also conducted. The GAF-based UHF RFID tags can thus lead to numerous applications in information exchange, tracking and tracing as well as the Internet of Things (IoT).

RFID over low cost VCSEL‐based MMF links: experimental demonstration and distortion study

Radio-over-fibre (RoF) distributed antenna system (DAS) technology has been investigated for the distribution of ultra-high frequency (UHF) radio frequency identification (RFID) signals. RoF DAS allows for reduced number of readers and centralised placement of readers which facilitates easy system maintenance, but it is important to find a low-cost solution that can achieve comparable performance to a conventional RFID system. In this work, a low-cost vertical-cavity surface-emitting laser (VCSEL)-based multimode fibre (MMF) link has been developed and demonstrated for passive UHF RFID applications. The reported results show almost the same performance when compared with a conventional RFID system. In addition, simple spatial antenna diversity schemes are tested, with improved performance reported in comparison with an RFID-RoF system without diversity. Also, an investigation of RFID over fibre with RoF non-linearity is carried out showing that phase-reversal amplitude shift keying (PR-ASK) RFID modulation allows for higher levels of RF carrier and modulated signal power than the ASK RFID, for low levels of non-linearity.

Standards for Passive UHF RFID

Passive ultra-high frequency (UHF) radio frequency identification (RFID) technology has been widely adopted by retail and other industries for serialized item-level identification and data sharing. This article introduces the standards that support and define all procedures in various passive UHF RFID applications. Electronic Product Code (EPC) Radio-Frequency Identity Protocols Generation-2 UHF RFID Standard, or C1G2, is a foundational standard that defines the format, encoding, and procedures within the air interfaces of RFID systems. Low Level Reader Protocol provides a standard and portable interface between different applications and RFID readers from different vendors. The format and encoding of the EPC information are defined by the EPC Tag Data Standard, which enables each tag to be uniquely identified (e.g., item-level identity of many goods in a warehouse). Additional protocols, such as Discovery, Configuration and Initialization and Reader Management, specify and clarify more processes (e.g., the management of many readers) that can be deployed in various business applications. We provide a general introduction of passive UHF RFID technology standards and review each protocol's features and procedures.

A dynamic data driven indoor localisation framework based on ultra high frequency passive RFID system

Better monitoring of workers' and the materials' flow within a production system can potentially enhance any facility's productivity and efficiency. This paper proposes a data driven framework to affordably localise indoor workers and materials using a passive radio frequency identification (RFID) system in large scale. Here, indoor wireless sensor networks are developed via passive Ultra-High Frequency (UHF) tags, where received signal strength indicator (RSSI) is measured by different access points (APs) to generate a fingerprinting database. Then, this database not only translates the signal strength reported by APs to distance through regression models but also helps to localise each tag utilising our proposed k-nearest neighbours (KNN) algorithm. Our improved KNN algorithm dynamically defines different neighbourhoods, in terms of size and topology considering environment status. Results from multiple experiments under different scenarios reveal that our proposed methods can detect and localise objects with an error as low as 0.36 m.

A dynamic data driven indoor localisation framework based on ultra high frequency passive RFID system

Better monitoring of workers' and the materials' flow within a production system can potentially enhance any facility's productivity and efficiency. This paper proposes a data driven framework to affordably localise indoor workers and materials using a passive radio frequency identification (RFID) system in large scale. Here, indoor wireless sensor networks are developed via passive Ultra-High Frequency (UHF) tags, where received signal strength indicator (RSSI) is measured by different access points (APs) to generate a fingerprinting database. Then, this database not only translates the signal strength reported by APs to distance through regression models but also helps to localise each tag utilising our proposed k-nearest neighbours (KNN) algorithm. Our improved KNN algorithm dynamically defines different neighbourhoods, in terms of size and topology considering environment status. Results from multiple experiments under different scenarios reveal that our proposed methods can detect and localise objects with an error as low as 0.36 m.

Time-Reversal Processing for Downlink-Limited Passive UHF RFID in Pulsed Wave Mode

This letter provides experimental evidence that, in a complex environment, a time-reversal processing of electromagnetic waves can increase the energy efficiency of the reader to tag communication and, hence, can increase the activation range of a passive ultrahigh frequency (UHF) radio frequency identification (RFID) system. A first experiment performed in a free-space environment shows that in addition to the classical continuous wave (CW) mode, a type AD222 passive UHF RFID tag can successfully operate in a pulsed wave (PW) mode using pulses with half-width 5 ns and period 35 ns. In a second experiment performed in a complex multipath environment, it is shown that the energy efficiency of the RFID system in the PW mode can be increased by applying a time-reversal (TR) processing strategy. Furthermore, it is shown that both PW and TR strategies involve less energy to activate the tag than the classical CW mode does. As a consequence, given a fixed amount of energy, TR processing can increase the activation range of the RFID system.

Glove-Integrated Passive UHF RFID Tags—Fabrication, Testing and Applications

Passive radio-frequency identification (RFID) technology enables versatile energy- and cost-efficient wireless platforms. We present passive ultra-high frequency (UHF) RFID tags integrated into normal work gloves for wearable RFID applications. The tags were designed to be functional throughout the global UHF RFID frequency range. The use environments of work gloves are challenging, for example due to moisture and mechanical stresses, which means the glove-integrated solutions have unique reliability issues to consider. We introduce 3-D printing of a flexible thermoplastic material directly onto the glove and embed electro-textile antennas and RFID microchip components inside the 3-D-printed structure. This manufacturing method solves the above-mentioned reliability challenges and enables the practical use of glove-integrated passive RFID tags. The performance of the fabricated glove-tags is first evaluated on a male test subject in an EMC room and in an office environment. Based on the wireless measurement results, the read ranges of the glove-tags are around 2–3 m throughout the frequency range of 800–1000 MHz. These results meet the requirements of many practical applications of glove-tags. Further, these glove-tags are found to endure extreme moisture and mechanical stresses, which supports their use in versatile use environments. Finally, the developed glove-tags are successfully tested in actual use situations for identification and access control. These results are very promising, especially considering the cost-effectiveness and the easiness of tag integration into different types of gloves.

A Multitag Cooperative Localization Algorithm Based on Weighted Multidimensional Scaling for Passive UHF RFID

Radio frequency identification (RFID) technology, which is one of the important implementation ways of Internet-of-Things (IoT), has achieved much attention in indoor localization areas. Passive ultrahigh frequency (UHF) RFID tag localization has a great development recently. Most of traditional passive UHF RFID localization algorithms can only achieve the position of one tag at a time while multitag localization is desired in many RFID applications. In this paper, we proposed the weighted multidimensional scaling (WMDS) based on received signal strength (RSS) method and the tag-to-tag communication system to achieve multitag cooperative localization. The targets are marked with passive UHF RFID tags. RSS method is used to determine the distance between readers and target tags through channel models. We can also obtain the estimated distances between target tags by the tag-to-tag communication system. The estimated locations of the tags are determined by the calculation of Euclidean distance matrix through a few iterations. Simulation results show that the WMDS algorithm achieves higher localization accuracy than traditional algorithms and the cooperation between tags improves the localization accuracy.

Gain Enhancement of a Looped Slots Patch Antenna for Passive UHF RFID Tags Applications in Metallic Supports

The objects with high conductivity such as metals consist of a challenge for passive RFID (Radio Frequency IDentification) tags in UHF (Ultra High Frequency) due to their effects on tags antennas performance. In this paper, a passive antenna for UHF RFID tags applications on metallic supports is presented. The antenna structure is constituted of a rectangular patch with looped slots printed on three-layer substrate and deposited on a regular ground plane. The looped slots are used to match the antenna impedance to the chip impedance in order to maximize power transfer. The three-layer substrate is adopted to improve the antenna gain, and the regular ground plane is added to act as fixed-size metallic plate. The antenna performance in free space and the one attached to the metallic surfaces are compared. The metallic plate size variation effects on antenna performance are studied by fixing the proposed antenna over different sizes of square copper plates which are multiple to the antenna size, and evaluated using the 3D electromagnetic simulator: HFSS (High Frequency Structure Simulator). The proposed antenna is designed to be used on high dimensions metallic objects such as the containers. It achieves a stable performance when the metallic surface size is five times larger than the antenna size: a read range of 16 m, an antenna gain about 2.5 dB and a bandwidth that covers all passive UHF-RFID band.

Multipath Mitigation Algorithm for Multifrequency-Based Ranging via Convex Relaxation in Passive UHF RFID

Radio frequency identification (RFID) is a promising technology in indoor localization. However, multipath cannot be avoided in indoor passive ultrahigh frequency RFID localization environment, which results in poor localization accuracy. In this paper, a range-based localization scheme has been developed to mitigate the effect of multipath errors and improve the localization accuracy. The proposed localization methods are based on semi-definite programming and second-order cone programming and do not require any statistics of multipath error. First, all the phase information of multifrequency is utilized. Dual-frequency phase difference of all dual-frequency combinations can be obtained to range. The ranging error is assumed to follow the Gaussian distribution. Then, convex relaxation methods with limiting the mean ranging error to one standard deviation of the Gaussian distribution are proposed. Finally, in order to solve the feasibility problem, the constraint of the mean ranging error is relaxed. Simulation results demonstrate that the proposed methods outperform some existing localization algorithms in multipath environment.

A Blind Calibration Method for Phase-of-Arrival-Based Localization of Passive UHF RFID Transponders

Phase-of-arrival-based localization systems for passive ultrahigh frequency (UHF) radio-frequency identification (RFID) transponders must typically be calibrated to account for unknown phase offset values. Usually, reference measurements are performed using known tag positions. However, if the measurement scenario changes or other types of transponders are used, the system must be recalibrated. This paper introduces an automatic blind calibration method based on a Viterbi algorithm that requires no reference measurements. With this approach, the phase offset values are determined autonomously based on the measurement data set without any prior knowledge of the transponder positions, which are also estimated. To prove the calibration approach, a multichannel system demonstrator was used comprising a commercial off-the-shelf RFID reader, conventional passive UHF RFID tags, eight transceiver front ends, baseband hardware, and signal processing. Measurements were carried out in a 2-D indoor office environment, which was defined to be 3.5 m $\times2.5$ m. Compared with the common exhaustive calibration method using reference measurements at known tag positions, the automatic blind Viterbi-based approach offers similar results with a root-mean-square deviation of the phase offset values of 0.33 rad, which corresponds to an electrical length of 18 mm. Regarding the localization, the experiments showed accurate results with a root-mean-square error of 56 mm and a median absolute error of 21 mm.

Passive UHF RFID Tag as a Sensor for Crack Depths

The use of ultrahigh-frequency (UHF) radio frequency identification (RFID) passive tags for defect detection is a promising application in structural health monitoring. However, it is a challenging task while most related information to tag antenna design is not available as well it suffers from the interference effect on wireless measurements. In this paper, we investigated and developed a new technique for crack depth sensing by using a passive UHF RFID tag as a sensor which interrogated by the ThingMagic M6e platform. The wireless power transfer level and the frequency sweeping are used to match between tag impedance and metal induction effect. The distance between the tag and reader is adjusted at 30 cm which can achieve high quality factor. As a result, the tag backscatter signal becomes rich with maximum peak components. The proposed technique called power peaks feature extraction (PPFE) is used to detect the artificial crack depth on the surface of the stainless steel and ferromagnetic samples. Skewness is applied on PPFE to offer a direct approximation procedure for the crack depth. A linear relationship of skewness achieves high-accuracy result with a maximum estimation error of 0.1 mm for stainless steel sample, the technique is validated and compared with the frequency-domain result, and it achieves all most the same accuracy for the stainless steel sample.