Reader Antenna Research Articles

Spatial Perception of Tagged Cargo Using Fused RFID and CV Data in Intelligent Storage

Radio-frequency identification (RFID) and computer vision (CV) technology are widely employed in intelligent storage systems for sensing, locating, identifying, and monitoring storage cargo. However, both of them have applicability scenarios and limitations. In this article, we propose a system for spatial perception of storage cargo based on the fusion of RFID and CV data. Specifically, we employ a mobile robot carrying an RFID reader and an RGB camera to move between shelves. The reader is connected to two vertically deployed antennas that receive phase values from the tags on the cargo to perform phase unwrapping. Then, we construct a linear system of equations to solve synthetic aperture radar (SAR)-based 3-D localization to obtain the location of the target tag efficiently and accurately. For the images of the shelves captured by the RGB camera, we use image localization techniques based on color and texture features to obtain the pixel coordinates of the cargo in the image. Since the sampling range of the RFID reader antenna is larger than the shooting range of the RGB camera, we use the coherent point drift (CPD) algorithm with threshold judgment to match the localization results of the two subsystems, enabling us to display the inherent information of the target cargo on the plane rendering. Our proposed system is evaluated through various experiments, and the results show that our localization algorithm achieves high accuracy in 3-D space, and the matching algorithm has high robustness to the number of cargo and missing cargo or tags.

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.

Failure Analysis of Abnormal Cracking of the Track Circuit Reader Antenna Baffle for High-Speed Trains.

The track circuit reader (TCR) is an important part of train control systems. This paper reports a failure of the TCR antenna baffle, which is used to prevent the TCR antenna from being struck by foreign objects. The designed service life of the baffle is 4.8 million kilometers, but serious cracking was found during routine maintenance after only 0.67 million kilometers of operation. In order to avoid the hidden danger brought by the incident to the safe operation of the train, it is necessary to conduct a complete failure analysis of the failed TCR antenna baffle. Therefore, a comprehensive investigation of the base material, cleaning agents, crack morphologies, etc., was carried out, and the failure environment of the antenna baffle was verified by experiment. The final results show that the environmental stress cracking is the root cause of the failed antenna baffle, and the multiple bubbles produced by the formed process of the antenna baffle are another important cause. According to the conclusions, the solutions to prevent the reoccurrence of such failures are proposed. After these solutions are adopted, the number of failed antenna baffles is greatly reduced, which fully proves the correctness of this analysis.

RAPP: A Radio Tomography Localization Method Characterized by Performance Parameterization in Rapid-Moving RFID System

Exploring and developing the perception system is an important means to promote the development of intelligent transportation. In this paper, we propose RAPP, a radio tomography-based method enabling performance parameterization to achieve parameter adjustment of localization accuracy without dense deployment of passive UHF RFID devices. The reader antenna takes a rapid-moving system as the carrier and generates virtual antenna elements to inventory received signal strength (RSS) of the pre-deployed tags. To eliminate the impact of the lack of tag backward signals during the mobile process and supplement the link distribution for each segment of the monitored platform, the Cubic Spline Interpolation algorithm (CSIA) is proposed to homogenize the spacing of the virtual antenna elements by preprocessing the measurements. Then the optimized link information is adopted to perform radio tomographic imaging to recognize the locations of targets. Theoretical analysis on ill-condition is derived to analyze how the number of virtual interpolation elements affects the localization accuracy. Further derivation about the relationship between the Bayesian Cramér-Rao Bound (CRB) and the link density provides a solution to influence the localization performance through parameter adjustment. Extensive simulation and experiment show that RAPP outperforms on multiple targets localization and behaves robustly in a multipath environment.

Circularly Polarized Cross-Dipole Antenna for UHF RFID Readers Applicated in the Warehouse Environment

In this paper, we proposed a broadband circularly polarized antenna with wide beamwidth. The main structure of the proposed antenna is a combined cross-polarized dipole antenna with four metal arms feeding by a single coaxial cable and two 90° phase delay lines. In order to attain a wide beamwidth antenna performance that can be used in a warehouse environment, we innovatively bent the metal arms and added a metal plane at a specific location to gain maximum beamwidth and the highest achievable gain. Especially, the application of folded metal arms not only reduce the space size of antenna, but also possess good axial ratio characteristic. The measurement illustrates that the antenna prototype achieves S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> < -10 dB impedance bandwidth (IBW) of 40% (820 - 1230 MHz), a 3-dB axial ratio bandwidth (ARBW) of 7.3% (895 - 970 MHz), and a maximum half-power beamwidth (HPBW) of 104° (@915 MHz). In addition, the good radiation characteristics of a gain of 6.33 dBic and an average radiation efficiency of 76.3% were measured in the operating bandwidth, in which make the antenna a good candidate for the hasty logistics radio frequency identification (RFID) system.

Improvement of Moving RFID Microtag Detection in Different Angular Orientations Using Multiple Tubular Coils

Directionality problem caused by the rolling of microtag with flowing fluid seriously affects the reliability of oilwell downhole radio frequency identification (RFID) system. In this paper, we propose a novel RFID reader antenna structure using multiple tubular coils for reduced orientation sensitivity. The conventional solenoid coil and saddle-coil pairs are combined to overcome the respective defects of the two coils and develop their advantages to form a complementary structure at the same time. Then, a series of coil parameters are designed in detailed to provide strong magnetic field distribution both in the x-axis, y-axis and z-axis directions. To verify the design, the proposed multiple tubular coils have been fabricated and measured. Experimental results demonstrate more potential than the conventional solenoid coil for microtag detection in different angular orientations, which is very important to improve the reliability and applicability of current oilwell downhole RFID system.

Integrated Wireless RFID Temperature Sensor for Biological Aortic Valve Prostheses

Body core temperature is one of the most reliable biometric indicators for monitoring the health status of a person. The gold standard in clinical settings is a highly invasive procedure involving the insertion of a catheter into the pulmonary artery, which receives blood directly from the core of the body. However, if a patient needs to host an Implanted Medical Device (IMD), a precise body core temperature measurement can be obtained without causing them additional discomfort, by adding communication and sensing capability to the IMD itself. This paper proposes a possible augmentation of a passive metal-free aortic valve prosthesis with a wrapped C-dipole provided by an RFID-based temperature sensor for batteryless and wireless temperature monitoring from the inside. A robust transcardiac link can be achieved with at least 24 dBm interrogation power by using a small on-skin reader antenna, which is also robust against moderate mutual misalignment among the two devices. The temperature sensing capability of a true sensorized valve, evaluated by means of a heated liquid phantom, demonstrated the possibility of sensing typical physiological temperature gradients with an average accuracy of less than 0.25∘C w.r.t. a reference thermocouple.

Localizing RFIDs in Pixel Dimensions

Radio Frequency IDentification (RFID) is emerging as a vital technology of the Internet of Things (IoT). Billions of RFID tags have been deployed to locate daily objects such as equipment, pharmaceuticals, vehicles, and so on. Unlike previous solutions that focus on localizing tagged objects in the world coordinate system in reference to reader antennas, this work exploits a system, called RFCamera, that can identify and locate RFID-tagged objects in images with pixel dimensions. Our core insight is that an image is a visual AoA profile in terms of lights, which is resulted from the pinhole camera model. Similarly, we generate an RF image derived from the AoA profile of a tag using the same pinhole model as the camera. Consequently, the locations of visual entities corresponding to tagged objects are highlighted by comparing two types of images. To this end, we customized a camera system equipped with a pair of rotatable reader antennas. Our experimental evaluation demonstrates that RFCamera enables a mean error of 5.7∘ and 2.9∘ at azimuth and elevation angle estimation, respectively. It can locate a visual entity with a mean error of 51 pixels (i.e., ≈1.3 cm at 96 dpi) in a 640× 480 image.

RoSense: Refining LOS Signal Phase for Robust RFID Sensing via Spinning Antenna

RFID sensing leveraging backscatter signal features (e.g., phase shift) from tags has gained increasing popularity in numerous applications but also suffers from negative impacts of environmental multipaths. Past works to address it rely on extra customized devices, labor-intensive offline training, or frequency channel hopping, all of which are non-ubiquitous or ineffective for real-life adoption. This article presents RoSense, a universal method to alleviate multipath reflections’ impacts by spinning the reader antenna, thus enabling more robust RFID sensing. Besides, RoSense requires no RF devices or offline training and operates in a nonintrusive manner. The key insight of RoSense is to exploit two properties of line-of-sight (LOS) signal when spinning the antenna, i.e., the linearity of phase changes and stability of received signal strength to attenuate the nonlinear and nonmonotonic effect of multipath signals and refine the phase shift of LOS signal. We have implemented a prototype of RoSense with COTS devices and studied two cases for evaluation: 1) material identification and 2) object localization. Experimental results show that RoSense can improve the material identification accuracy by up to 16.22% and reduce the mean localization error by up to 39.93%, greatly outperforming the state-of-the-art solutions.

Displacement Estimation Using 3D-Printed RFID Arrays for Structural Health Monitoring.

Radio frequency identification (RFID) tags are small, low-cost, wearable, and wireless sensors that can detect movement in structures, humans, or robots. In this paper, we use passive RFID tags for structural health monitoring by detecting displacements. We employ a novel process of using 3D printable embedded passive RFID tags within uniform linear arrays together with the multiple signal classification algorithm to estimate the direction of arrival using only the phase of the backscattered signals. We validate our proposed approach via data collected from real-world experiments using a unipolar RFID reader antenna and both narrowband and wideband measurements.

Multidisciplinary development of Smart Jacket for elder care

Limitations in physical and cognitive functioning are common among elderly people. Due to these limitations, activities of daily living, such as dressing, can be difficult, even with the help of another person. The limitations may also challenge using the assistive tools meant to support the independent living of elderly people. One significant assistive tool is a nurse call -button whose aim is to support the elder’s independent living and ensure the assistance of others when needed. In severe cases, using of such assistive tools is entirely prevented because of the user’s limited abilities. The purpose of this study was to create a solution for the above-mentioned challenges with smart clothing. The objectives of this study were to design a Smart Jacket that 1) is easy to put on and 2) includes an easy-to-use nurse call button. The product development utilized design thinking through four different Smart Jacket versions, three of which were evaluated in multidisciplinary design workshops. The newly designed and created upper-body garment with assistive zippers in the sleeves can be put on when assistance is available without any movement of the user’s upper limbs. Further, the developed passive RFID (radiofrequency identification)-based jacket with integrated nurse call -button is functional without an on-jacket energy -source and is thus maintenance free. The nurse call -button is functional more than four meters from an RFID reader antenna. Based on the initial expert evaluations, the developed Smart Jacket could operate as part of a bigger safety system, for example in an elderly care unit or domestic care, bringing a needed new alternative as merged nurse call -button and assistive cloth.

UHF RFID reader antenna with switchable far‐field and near‐field working state

An ultra-low profile and high-performance UHF RFID reader antenna is proposed in this letter, which can be switched between far-field (FF) and near-field (NF) operative modes. This antenna is composed of four dipoles and a reconfigurable feed network. The four dipoles form a square, and the feed network is located in the centre. The feed network is a four-way power divider, and the phase of the output signal can be controlled by switching diodes. As a balanced structure, double-sided parallel-strip lines (DSPSLs) are used to feed four dipoles. Compared to the balun structure, the application of DSPSLs can reduce the area of the feed network, thereby reducing the influence of the feed network on the central magnetic field. Experimental results show that the proposed antenna can provide a NF reading area of 180 × 180 mm2, and the identification rate can reach 100% within 30–60 mm height. The FF gain of the antenna is 4.7 dBic, and the overlapping range of 3 dB AR bandwidth and −10 dB impedance bandwidth is 800–960 MHz. The good FF and NF performance of this antenna is conducive to its application in RFID systems.

Optimization Method of RFID Reader Antenna Deployment in Obstacle Environment Based on Improved FA

The aim of this study is to solve the problem of RFID reader antenna deployment when an obstacle in the environment or the material itself is an obstacle. The article establishes a new reader antenna constraint model based on the rectangular obstacle RFID antenna deployment optimization environment model and the reader antenna sensing model containing Gaussian distribution noise probability and applies the improved firefly algorithm to find the optimum with coverage rate, interference degree, and load balance function as multiobjective functions. First, to obtain a uniform traversal of the target space, and a cube mapping is applied for chaos initialization. Second, a weighting model is proposed to control the speed of firefly variation and combine the variable step strategy of elite individuals to expand the movement step of elite individuals and reduce the movement step of nonelite individuals to improve population diversity. Finally, to improve the algorithm’s continuous optimality-seeking ability, a Gaussian variation operation strategy based on elite fireflies is introduced to ensure the algorithm’s optimality-seeking throughout the process.

A high gain wideband array antenna based on metasurface for ETC application

Free flow electronic toll collection (FFETC) has played an important role in building convenient and safe transportation systems in many countries. The most challenging problem when researching and developing this system is shortening the payment cycle so that vehicles passing through the stations do not need to stop or keep going at a speed greater than 60 Km/h. Designing roadside unit (RSU) reader antennas with high gain and suitable radiation pattern is the most feasible and economical solution. This paper proposes a left-handed circularly polarized (LHCP) 2×4 array antenna using sequential phase rotation power dividers at 5.8 GHz band. The element antenna is a square patch antenna with a slit in the middle for better impedance matching, six trapezoidal parasitic patches added to either side of the main patch to create resonance at high frequencies, and a metasurface placed on top of the main patch. The proposed metasurface is a 4×4 array of dual circular unit cells to improve gain and extend axial ratio (AR) bandwidth. The proposed antenna array has a high gain of 17 dBi, -3 dB vertical and horizontal beamwidths of 33.20 and 17.10, which cover over one lane, are expected for any ETC system to avoid interference with other lanes. Impedance bandwidth and AR bandwidth are 2.19 GHz (37.75%) and 2.06 GHz (35.52%), respectively. The overall dimensions of the proposed array antenna are approximately 152×76×6.4 mm3. With the above merits, this antenna is a suitable candidate for the RSU reader antenna in the FFETC

Orientation-Insensitive Chipless RFID Achieved in Multiple Rotational Degrees of Freedom

Frequency-coded chipless radio frequency identification (RFID) suffers from resonant frequency detuning caused by misaligned orientations. The literature has employed topological symmetry to prevent shape variations; however, this scheme is effective only for the orientation in roll and cannot address other rotational degrees of freedom, including pitch and yaw. This study takes the first step to cope with the orientation mismatch against arbitrary roll, pitch, and yaw angles. The proposed technique requires the design of tag and new reader architecture, eliminating complex signal processing. The tag comprises resonators with the pattern of a short dipole. Two reader antennas are placed orthogonally and fed with equal power, illuminating co-polarized electromagnetic waves toward the tag. Based on the Pythagorean trigonometric identity, the sum of the backscattering power is unvarying against the rotations in pitch or yaw. The proposed technique is experimentally validated using a 6.97 bit system. When orientation mismatch in yaw appears, the proposed scheme improves the read reliability from 54.3% to 93.5%. Moreover, when mismatch in both roll and yaw occurs, the reliability is improved from 43.8% to 91.8%. Practical aspects, including various detection zones and the loading effect, are also analyzed.

UHF-RFID-Based Real-Time Vehicle Localization in GPS-Less Environments

The vehicle localization, which aims to identify a vehicle and then position the vehicle with a high precision, can be used to facilitate various applications and services in vehicular networks. Unfortunately, conventional localization systems, e.g., global positioning system (GPS), hardly meet the accuracy requirements especially in certain specific scenarios, such as tunnels. At the same time, Ultrahigh frequency (UHF) radio frequency identification (RFID) has become an efficient booster for internet of things (IoT) due to the desirable advantages, such as low cost, battery-free, and unique identification. In this paper, based on the UHF-RFID, we propose a novel real-time vehicle localization scheme in GPS-Less Environments. Considering the practical implementation of multiple RFID reader antennas on a vehicle is constrained, we adopt single antenna multi-frequency ranging scheme, in which the integer ambiguity problem is solved by the maximum-likelihood estimation (MLE)-based robust Chinese remainder theorem (CRT). With the reconstructed distances between the tags and the reader, the coordinates of the vehicle then can be calculated with the Levenberg-Marquardt (LM) algorithm. Furthermore, the computational complexities of the algorithms and the time consumption of the proposed scheme are analyzed. The experimental results demonstrate that the proposed scheme can track vehicle’s location with error lower than 27 cm at the probability of 90%.

Iron oxide-immobilized porous carbon nanofiber-based radio frequency identification (RFID) tag sensor for detecting hydrogen sulfide

Hydrogen sulfide (H2S) is the richest and stinkiest toxic gas found around coal mines, manholes, and semiconductor industries. However, there are not many studies on H2S detection around various industrial sites using wireless sensors. This study proposes an H2S wireless sensor system that communicates of the reader antenna and the sensor tag using 904 MHz activated radio frequency identification (RFID). The sensor tag is formed through an iron oxide-immobilized multiscale pore contained carbon nanofiber (Fe2O3-MPCNF)-based conductive paste. This wireless sensor tag has a large detection range (0.2 to 100 ppm) at 25 °C, is very sensitive to H2S gas (0.2 ppm or less), and is inexpensive to process. In addition, the sensor tag has a long operating range (5–40 cm) and excellent flexibility, and has excellent cycle stability (up to 35 days), making it practical for wearable devices for wireless detection.

A novel circularly polarized reader antenna design for UHF RFID applications

A novel circularly polarized reader antenna design for UHF RFID applications

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.

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

An optically transparent circularly polarized (CP) radio frequency identification (RFID) antenna is presented in this paper. The RFID antenna consists of a coplanar-fed waveguide inverted L-shaped monopole with a dual feeding structure. The CP wave with a bidirectional radiation pattern is obtained by feeding the radiator at both ends. The transparency of the antenna is obtained by using fluorine tin oxide (FTO) coated soda-lime glass substrate. The proposed antenna operates at a Universal RFID frequency (800–1100 MHz) with circular polarization. The antenna has an impedance bandwidth of 300 MHz and an overlapped 3-dB axial ratio (AR) bandwidth of 110 MHz (860–970 MHz, 12% centered at 915 MHz). It has a peak realized gain of 1.4 dBic. The antenna with the size of 100 × 100 mm2 is designed for ultrahigh-frequency RFID reader applications.