Passive UHF Radio Frequency Identification Tags Research Articles

An AOA and Orientation Angle-Based Localization Algorithm for Passive RFID Tag Array

This paper proposes an indoor localization algorithm based on AOA (Arrive of Angle) and orientation angle (OA) for passive UHF RFID (Ultra-High Frequency Radio Frequency Identification) tag array. By utilizing a uniform linear tag array (ULA), the AOA, which is defined as the angle of the reader relative to the tag array, can be estimated by the Multiple Signal Classification (MUSIC) algorithm. The relationship between AOA, OA of the tag array, and the direction angle (DA) between each reader antenna to the geometric center of the tag array is analyzed, and an OA retrieval method based on rotating the coordinate system is proposed to calculate DA. The tag array localization is finally acquired by the DA of each antenna. Simulation and experiment results show that the proposed algorithm can achieve decimeter-level localization accuracy. The proposed algorithm achieves a mean accuracy of 0.216 m, which is a significant improvement compared with the traditional AOA localization algorithm.

Efficient localization in warehouse logistics: a comparison of LMS approaches for 3D multilateration of passive UHF RFID tags

The Fourth Industrial Revolution, or Industry 4.0, aims at automating traditional manufacturing and industrial practices using modern smart technology. Autonomous mobile robots equipped with different sensors and employing different techniques have been proposed in the literature in the logistics and inventory warehouse management contexts. Efficient robot motion and planning depend on precise localization, mapping, and awareness of the environment. To properly localize items, recent attempts have been made employing radio frequency identification (RFID) in a 3D environment. This manuscript introduces four least mean squares methods to estimate the 3D positions of tags employing synthetic apertures and phase unwrapping. The proposed methods approach the localization problem solving a system of equations typical of multilateration methods to find the intersections of multiple hyperboloids. The novelty introduced here is the use of unwrapped phase distances to compute pseudo ranges for the multilateration problem. The use of such a technique is feasible thanks to precise mobile robot localization and custom navigation policies. All the analyzed methods are suitable for online localization due to reduced computation timings and have been tested on three different datasets. Two of them contain virtual data that has been generated by simulation, while the other one comes from an indoor experimental setup. Simulated tests show that combined antenna motions in 3D space (including Z-axis) improve the localization obtaining errors under the centimeter for 3D localization. Experimental tests obtained results as low as 13 cm of mean accuracy for 3D localization and 0.21 cm for 2D localization.

Using the zeroth order resonance of an inter‐digital capacitive unit‐cell to design antennas for passive UHF RFID tags

Meander-line and multi-layer antennas have been used extensively to design compact UHF radio-frequency identification (RFID) tags; however the overall size reduction of meander-line antennas is limited by the amount of parasitic inductance that can be introduced by each meander-line segment and multi-layer antennas can be too costly. In this paper, a new compact antenna topology for passive UHF RFID tags based on zeroth order resonant (ZOR) design techniques is presented. The antenna consists of lossy coplanar conductors and inter-connected inter-digital capacitor (IDC) unit-cells with a ZOR frequency near the operating frequency, which is a key component in the design process because the unit-cells chosen for the design are inductive at the operating frequency. This makes the unit-cells very useful for antenna miniaturization. The new design in this work has several benefits; namely the coplanar layout can be printed on a single layer, matching inductive loops that reduce antenna efficiency are not required and ZOR analysis can be used for the design. Finally, for validation, a prototype antenna was designed with a unit-cell ZOR resonant frequency of 900 MHz, fabricated and characterized. A maximum read-range of 7.6 m was determined.

Non-Line-of-Sight Localization of Passive UHF RFID Tags in Smart Storage Systems

The UHF radio-frequency identification (RFID) has gained growing attention for tagged object localization in smart storage systems. Due to Non-Line-Of-Sight (NLOS) condition, it is challenging to accurately locate the position of tags inside closed spaces. In this paper, we propose a precise and cost-effective solution for tagged object localization in closed spaces, using only received signal strength (RSS) information. We establish a RSS profile for each tag and discover some important features of RSS profiles including uniqueness, time-variation, column-dependence and waveform-similarity. Based on these features, we propose a reference-free RSS-profile (RFRP) localization scheme. The advantage of our propose scheme is to accurately localize multiple tags in closed spaces by overcoming the challenges including the lack of pre-deployed reference tags, NLOS propagation, multi-path propagation and coupling effect. The RFRP scheme first roughly estimates tags’ coordinates based on Peak Asymmetry Factor, then acquires reference-tag substitutes through the similarity of RSS sequences. Subsequently, our scheme refines the relative positions of all tags by these substitutes. Finally all tags’ absolute positions are estimated through a RSS-ranging model. Extensive experiment results demonstrate that our approach can achieve high ordering accuracy and localization accuracy for the tags inside closed spaces.

A Standalone RFID-Based Mobile Robot Navigation Method Using Single Passive Tag

This article proposes a standalone radio frequency identification (RFID)-based mobile robot navigation method, in which a mobile robot equipped with reader antennas can be continuously guided to a static object marked with a single passive UHF RFID tag. An observation model based on the RFID phase difference is built and integrated into a particle filter, by which the instantaneous relative position between the mobile robot and the tagged object can be detected in real time. Based on the position information extracted from the RFID system, the mobile robot adjusts its pose to move toward the RFID-tagged object. Compared with the existing RFID-based mobile robot navigation methods, the proposed method requires no external sensors other than the RFID and requires only a single passive tag. Experiments using commercial off-the-shelf (COTS) RFID devices are performed, and the results indicate that the mobile robot can satisfactorily realize navigation task with a distance accuracy of 4.04 cm and a bearing accuracy of 2.23°. The proposed method is well applicable for the navigation scenes in which the absolute position of the tagged target object is not known beforehand. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —UHF radio frequency identification (RFID) has been widely applied as an asset management ID sensor in many fields. RFID-based mobile robot navigation technology can further increase its application value as a location sensor. This article proposes a standalone RFID-based mobile robot navigation method, in which the reference tag and the external sensors other than RFID are both not required. In the proposed method, only a single passive tag is attached to the static target object. Experimental results indicate that the proposed method can enable navigation task with good performance in situations in which the absolute navigation goal position is not known in advance.

Different Substrate Materials for Designing a Passive UHF RFID Tag Antenna

The Radio Frequency Identification (RFID) technology has been increasingly used for various application such as tracking of products, smart cards, identification, item management, security etc. In this paper, the performance parameter of the passive UHF RFID tag antenna has been studied for four different substrate materials viz., FR4 epoxy, PET, Rogers 4350, Taconic TLY materials. A simple meandered dipole antenna has been designed using a T-match stub for impedance matching of the tag antenna with the attached RFID chip. These different substrates are then designed separately, for the same antenna geometry. The effect of using these substrates on RFID tag antenna parameters such as reflection coefficient, antenna gain, VWSR, radiation pattern, impedance, ease of optimization level, read range, and radiation efficiency are then observed.

Similarity Analysis-Based Indoor Localization Algorithm With Backscatter Information of Passive UHF RFID Tags

Passive radio frequency identification (RFID) is a low cost and low complexity localization technology. With introduction of reference tags, RFID technology can provide on-line reference information for pattern matching localization algorithms. One of the most popular algorithms is $k$ -nearest neighbor algorithm. While how to decide the $K$ value in estimation is still a problem. In addition, traditional received signal strength indicator (RSSI)-based algorithms suffer from multipath effects, it is difficult to further improve the localization accuracy. In this paper, we analyze the similarity of backscatter signals and present a novel range based indoor localization method, SAIL. According to the propagation distances of signals, reference tags that have similar distances to a reader antenna can be considered as a group. Inspired by the idea of grouping, clustering algorithm is utilized to get candidate tags for ranging. This method does not need to fix the number of reference tags in estimation. Besides RSSI, the RFID reader can also extract phase of signals coming from backscattered signals of responding tags. This guides us to combine RSSI and phase in similarity measure for clustering. In the simulation and experimental tests, SAIL is superior to other RFID schemes considering cost, location estimation error, and flexibility.

Localization of Passive UHF RFID Tags Using the AoAct Transmitter Beamforming Technique

The localization of passive ultra-high frequ- ency (UHF) radio frequency identification (RFID) tags is an emerging technology that has reached a high level of interest in industry and research. Most solutions use classical techniques, such as the angle-of-arrival or the received-signal-strength methods. As an alternative, we present a new approach for estimating the position of a passive UHF RFID tag by using a transmitter beamforming technique that we call angle-of-activation (AoAct). It is based on manipulating the shape of the radiation pattern of the interrogator’s transmitter antenna array. By pivoting the main lobe of the pattern in the azimuth plane of the array and by utilizing the very sensitive response threshold of passive UHF RFID tags, we are able to estimate the tag direction. We use three-channel digital beamforming, where the phases and amplitudes of the antenna array’s feeding radio frequency signals are controlled by the baseband $I$ and $Q$ components of the interrogator’s transmitter signal. Our self-developed hardware pivots the main lobe of a three-element antenna array in a range of ±52° with a resolution of 0.02°. It senses the AoAct with a mean measured accuracy of 1.2° in the anechoic chamber, 1.9° in a basic multipath environment, and 2.5° in a real-world multipath environment. After estimating the AoAct of a tag from different locations, the tag position is triangulated. Experiments show that our AoAct system delivers a localization accuracy of 7 cm in a typical multipath environment.

SPARTACUS: Self-Powered Augmented RFID Tag for Autonomous Computing and Ubiquitous Sensing

In recent years, besides the advances made in canonical UHF radio-frequency identification (RFID) technology, intense research efforts are being made to design new passive augmented tags that enable RFID-based sensing. These efforts stimulate continued research aimed at providing tags with additional functionalities, besides identification and sensing. In this work, an innovative device, representing a new class of fully passive augmented UHF RFID tags, is presented. It is named SPARTACUS, an acronym for self-powered augmented RFID tag for autonomous computing and ubiquitous sensing. The device, based on an accurate electromagnetic design that exploits polarization diversity of two antennas, which perform both energy harvesting and communication, enables a full two-way proactive interaction with any standard RFID Class-1 Generation-2 reader. It conjugates identification, sensing, local computing, and actuation control, besides being compact, energy-efficient, and easy to use. This paper presents detailed designs of both RF interfaces and digital section, besides discussing system validation and performance evaluation, followed by demonstrating the significance of SPARTACUS in paving the way to new classes of applications in the Internet of Things.

Fully Integrated Passive UHF RFID Tag for Hash-Based Mutual Authentication Protocol

Passive radio-frequency identification (RFID) tag has been used in many applications. While the RFID market is expected to grow, concerns about security and privacy of the RFID tag should be overcome for the future use. To overcome these issues, privacy-preserving authentication protocols based on cryptographic algorithms have been designed. However, to the best of our knowledge, evaluation of the whole tag, which includes an antenna, an analog front end, and a digital processing block, that runs authentication protocols has not been studied. In this paper, we present an implementation and evaluation of a fully integrated passive UHF RFID tag that runs a privacy-preserving mutual authentication protocol based on a hash function. We design a single chip including the analog front end and the digital processing block. We select a lightweight hash function supporting 80-bit security strength and a standard hash function supporting 128-bit security strength. We show that when the lightweight hash function is used, the tag completes the protocol with a reader-tag distance of 10 cm. Similarly, when the standard hash function is used, the tag completes the protocol with the distance of 8.5 cm. We discuss the impact of the peak power consumption of the tag on the distance of the tag due to the hash function.

Modified RSSI Technique for the Localization of Passive UHF RFID Tags in LOS Channels

This paper presents a new approach for improving the localization of passive ultra high frequency radio frequency identification (RFID) tags in line-of-sight channels using a received signal strength indicator (RSSI) technique. In practice, the complex propagation in the indoor channels and also the variability of some parameters of the RFID equipment itself introduces significant amount of errors when the operation of localization carries out the RSSI technique. Indeed, as the calculation is based on a trilateration, the incomplete knowledge of the propagation and some parameters of RFID tags leads to estimate distances which are wrong, and therefore the localization cannot be correct. In order to overcome this drawback, the proposed method takes into account the presence of unknown parameters relying on a dichotomous algorithm which includes probabilistic parameters. The presented simulation results are in good agreement with the expected theoretical results. Experimental results show that the proposed method strongly increases the accuracy of the estimated position of tags. Compared to other approaches based on the improvement of the RSSI technique, this method does not require too much complexity in terms of materials (no need for specific architecture or reference tags) and processing (fast and simple algorithm).

Passive UHF RFID Tag for Heat Sensing Applications

A possible method of utilizing paraffin wax as a substrate material in developing a threshold heat sensing radio frequency identification (RFID) tag is discussed. A small narrowband passive UHF RFID tag is made on top of a multilayer substrate. Paraffin wax acts as the main heat sensitive layer of the substrate. The properties and characteristics of the paraffin layer change due to heat. The narrowband tag on top of the substrate is designed to be sensitive enough to detect any structural and physical changes of the substrate material. The changes in the properties of the substrate material will cause a shift in the operating frequency of the tag. This frequency shift will reduce the performance of the narrowband RFID sensor tag. The change in the properties of paraffin wax after being exposed to heat is irreversible under normal conditions and therefore, the proposed RFID tag can be referred to as a threshold heat sensing device. Such a low-cost solution can be useful in detecting heat exposures in various supply chains and transportation mishandling of heat sensitive items.

Design, development, and performance evaluation of a compact and long‐range passive UHF RFID tag

AbstractPassive radio frequency identification (RFID) tags can be classified in terms of reading range.Short‐range tags communicate with the reader up to a few centimetres. Medium‐range tags reach almost 5 meters. Long‐range tags work properly up to almost 12 meters. Nevertheless, the longer is the working distance, the larger is the tag size. In this work, a new passive UHF RFID tag has been designed, realized, and tested. Based on the joint use of various design and miniaturization techniques, our device is as compact as a medium‐range tag. The tag prototype has been extensively tested and compared with both a commercial medium‐range tag with similar size and a well‐performing long range tag. For all such tags, measurements of received signal strength indication, working range, tag sensitivity, and differential radar cross section have been carried out and compared. Results are impressive. Despite the compactness of the proposed tag, its performance is appreciably better than the medium‐range tag and even comparable with the tested long range one. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1335–1339, 2012

Passive UHF RFID-Based Localization Using Detection of Tag Interference on Smart Shelf

In this paper, we present a novel radio-frequency identification (RFID) smart shelf that accurately locates tagged objects using standard passive UHF RFID tags. This standard-based commercial off-the-shelf approach provides significant advantages over custom HF RFID and other near-field RFID approaches, including reduced tag costs, minimal infrastructure costs, and simple operation. In order to achieve accurate location sensing of objects sitting on the shelf, we utilize a novel localization algorithm that utilizes detected changes in a tag's readability to infer the presence of neighboring tags. According to our experimentation results, with a single RFID reader antenna for two wooden shelves of size 91 cm × 152 cm, our smart-shelf system estimates nine box-level object locations with an average error of just 18.48 cm, which is a 71% improvement in accuracy compared with the previously published k nearest neighbor (KNN) algorithm.

Multipacket Reception of Passive UHF RFID Tags: A Communication Theoretic Approach

This paper develops a communication theoretic model for the design and analysis at the physical layer of a reader receiver structure for passive UHF Radio Frequency IDentification (RFID). The objective is attaining multipacket reception capabilities which in turn help the fast resolution of multiple tags through a more rapid and power efficient arbitration of the tags collisions. In particular, we derive a parametric continuous time model for the subspace of a tag signal at the noisy receiver/reader, which in addition to being affected by fading and receiver delay, exhibits wide variations in the symbol frequency and transmission delay, due to imperfections in the RFID hardware design. Our main contribution is in showing that channel fading, the difference in delay and the tags frequency dispersion can be transformed from foes to friends by exploiting them in a multipacket receiver. In fact, signals colliding from different tags are more easily separable by estimating the sensor specific variation in frequency and delay and using these estimates in a multiuser receiver. In our study, we specifically consider a successive interference cancellation algorithm followed by a maximum likelihood sequence decoder, that iteratively reconstructs one signal contribution at a time and then removes it from the received signal. Numerical simulations show that the estimates and proposed algorithm are effective in recovering collisions. The proposed algorithm is then incorporated into a numerical simulation of the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> -protocol for UHF RFID tags and is shown to be effective in providing fast and power efficient arbitration.

Using Meander Open Complementary Split Ring Resonator (MOCSRR) Particles to Design a Compact UHF RFID Tag Antenna

In this letter, a new printed dipole that uses series-connected meander open complementary split ring resonator (MOCSRR) particles is introduced. It is shown that by using the antenna presented here on a prototype passive UHF radio frequency identification (RFID) tag, useful read ranges up to 4.1 m can be achieved. The printed dipole on the prototype resonates at an overall dimension of approximately 0.1λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the free-space wavelength at resonance. The equivalent circuit of each MOCSRR particle is extracted and compared to the equivalent circuit of an open complementary split ring resonator (OCSRR) particle with the same overall dimensions and an OCSRR particle with larger overall dimensions. It is shown that the MOCSRR particle resonates at a lower frequency than both of the OCSRR particles, thus contributing to the lower resonant frequency of the antenna. The read range of the prototype is comparable to other passive UHF RFID tags with dimensions that are up to twice the overall size.

Measurement of the passive UHF RFID tag’s performance based on software-defined radio

The signal transmission and measurement method of the passive UHF radio-frequency identification(RFID) system are discussed in this paper. Part of tags communication performance which conforms with the ISO/IEC 18000-6 Type C was obtained by using the software-defined radio test platform. The received power by the platform changes with the communication parameters. Sensitivity of different tags was tested. All experiments were conducted under normal conditions.The measurement results show that the small Tari, half duty cycle (PW) and higher modulation index in baseband signal encoding allow the RFID system to receive larger power, also the RFID system to have larger read range.

Design of an ultra-low-power digital processor for passive UHF RFID tags

A new architecture of digital processors for passive UHF radio-frequency identification tags is proposed. This architecture is based on ISO/IEC 18000-6C and targeted at ultra-low power consumption. By applying methods like system-level power management, global clock gating and low voltage implementation, the total power of the design is reduced to a few microwatts. In addition, an innovative way for the design of a true RNG is presented, which contributes to both low power and secure data transaction. The digital processor is verified by an integrated FPGA platform and implemented by the Synopsys design kit for ASIC flows. The design fits different CMOS technologies and has been taped out using the 2P4M 0.35 μm process of Chartered Semiconductor.

A Compact Meander-Line UHF RFID Tag Antenna Loaded With Elements Found in Right/Left-Handed Coplanar Waveguide Structures

A new planar meander-line antenna for passive UHF radio frequency identification (RFID) tags is presented. Specifically, a meander-line antenna is loaded periodically with coplanar waveguide (CPW) LC elements traditionally found in right/left-handed waveguide structures. It is shown that by using the antenna presented in this letter in a prototype passive UHF RFID tag, effective read ranges up to 4.87 m can be achieved. Many different dielectric substrates and CPW-LC load dimensions are investigated to illustrate how the input impedance, gain, and overall dimensions of the antenna are affected by these structural differences. It is shown that the overall dimension of the meander-line antenna can be reduced by slightly more than 18% with the introduction of the CPW-LC elements to the design. Several of the simulation results are validated by comparison with measurements.

Characterisation of RF propagation in rectangular metal pipes for passive RFID systems

In this paper, we collect and extend the theory of Radio Frequency (RF) propagation within rectangular metal pipes. This work is motivated by the need to understand the operation of UHF Radio Frequency Identification (RFID) systems when the tags are placed within rectangular metal pipes. The field components inside a rectangular metal pipe are derived to obtain the propagation and attenuation constants, modal cutoff frequency relationships, the different Transverse Electric (TE) and Transverse Magnetic (TM) modes. The cutoff frequencies, attenuation and angle of incidence are used within the theory to identify operating limitations of passive RFID systems in hollow rectangular metal pipes. This theory is combined with existing theories of propagation within cylindrical metal pipes to present a comprehensive general theory. Analytical evaluations are used to visualise the tags within the metal pipes and to validate the theory presented in this paper. It is shown that passive UHF RFID tags can be read even below the cutoff frequencies of these rectangular metal pipes when used under the guidance of the general theory.