Chipless Radio Frequency Identification Research Articles

Design of low-cost humidity sensor based on chipless RFID

It is of great significance to design a low-cost chipless radio frequency identification(RFID) sensor for environmental humidity monitoring. To this end, polyvinyl alcohol (PVA) film is used as a humidity sensitive material, and the overall size of the rectangular substrate is 18 mm × 18 mm ×0.5 mm. Through the humidity sensing principle and simulation analysis, the change of environmental humidity causes the change of the dielectric constant of the humidity sensitive material PVA, which in turn affects the resonant frequency offset of the entire sensor. The simulation results show that the relative humidity working range of the designed humidity sensor is 21.9% ∼ 52.5%, the corresponding sensor resonant frequency range is 2.76 ∼ 2.51GHz, the total offset reaches 250 MHz, and the average sensitivity at the maximum relative humidity is 23.08MHz/% . The designed humidity sensor has the advantages of miniaturization, simple structure and low cost, and can be used for humidity monitoring in various target environments. Keywords.low cost; chipless RFID humidity sensor; polyvinyl alcohol; humidity monitoring; humidity sensitive material.

Use of Chipless Radio Frequency Identification Technology for Smart Food Packaging: An Economic Analysis for an Australian Seafood Industry

Effective monitoring of perishable food products has become increasingly important for ensuring quality, enabling smart packaging to be a key consideration for food companies. Among the promising technologies available for transforming packaging into intelligent packaging, chipless radio frequency identification (RFID) sensors stand out. Despite the high initial implementation costs associated with chipless RFID technology, the potential benefits could outweigh the costs if electrical challenges can be overcome. We examine various economic methods to analyze the economic benefits of chipless RFID technology, evaluating the benefits of using this technology for the quality monitoring of seafood products of an Australian seafood producer, Tassal. The analysis considers three primary business drivers, viz. quality monitoring, operational efficiency, and tracking and tracing, using net present value and return on investment as the key indicators to assess the feasibility of implementing the technology. Based on sensitivity analysis, we suggest chipless RFID technology is currently best suited for large firms facing significant quality monitoring and operational efficiency challenges. However, as the cost of chipless RFID sensors decreases with further development, this technology may become a more viable option for small businesses in the future.

Efficiency Improvement for Chipless RFID Tag Design Using Frequency Placement and Taguchi-Based Initialized PSO.

Frequency encoding chipless Radio Frequency Identification (RFID) tags have been frequently using the radar cross section (RCS) parameter to determine the resonant frequencies corresponding to the encoded information. Recent advancements in chipless RFID design have focused on the generation of multiple frequencies without considering the frequency position and signal amplitude. This article proposes a novel method for chipless RFID tag design, in which the RCS response can be located at an exact position, corresponding to the desired encoding signal spectrum. To achieve this, the empirical Taguchi method (TM), in combination with particle swarm optimization (PSO), is used to automatically search for optimal design parameters for chipless RFID tags with a fast response time, to comply with the frequency encoding requirements in the presence of the mutual coupling effect. The proposed design method is validated using I-slotted chipless tag structures that are fabricated and measured with different sets of resonant frequencies.

Analysis of Reader Orientation on Detection Performance of Hilbert Curve-based Fractal Chipless RFID Tags

The role of the orientation of the radio frequency identification (RFID) reader is vital in the RFID-based communication system. This study presents the design and analysis of the impact of the orientation of the RFID reader (angle of incidence of the plane wave) on the detection and sensitivity characteristics of fractal chipless RFID tags. Four fractal (irregular) shaped tags are developed using four iterations of the Hilbert curve filling algorithm. The full-wave EM analysis of the designed tags in Matlab is performed by exporting them in Computer Simulation Technologies Micro-Wave Studio (CST MWS) in the frequency range of 2 to 20 GHz. Firstly, the performance of the tags is analyzed by observing the radar cross-section (RCS) of the tag for the fixed orientation of the incident plane wave in three different polarizations (horizontal, vertical, and oblique). Later, the variations in the EM spectrum (RCS results) are analyzed for oblique polarization by varying the incidence plane wave in both elevations (for two cases of 0∘ and 90∘) and azimuth planes (sweeping from 0∘ to 180∘ with a step size of 10∘). The analysis of the proposed aggregated RCS response for all cases in oblique polarization produces higher coding capacity (169 bits), coding spatial capacity (16.504 bits/cm2), coding spectral capacity (9.826 bits/GHz), and coding density (0.960 bits/GHz/cm2) for the realized highly irregular tag using fourth-iteration (4T) of Hilbert curve filling algorithm. The proposed procedure of detection based on aggregated response makes the developed RFID communication system more secure and reliable.

A Concise State-of-the-Art Review of Crack Monitoring Enabled by RFID Technology

Cracking is an important factor affecting the performance and life of large structures. In order to maximize personal safety and reduce costs, it is highly necessary to carry out research on crack monitoring technology. Sensors based on Radio Frequency Identification (RFID) antennas have the advantages of wireless and low cost, which makes them highly competitive in the field of structure health monitoring (SHM). Thus, this study systematically summarizes the research progress of crack monitoring based on RFID technology in recent years. Firstly, this study introduces the causes of cracks and the traditional monitoring methods. Further, this study summarizes several main RFID-based crack monitoring and detection methods, including crack monitoring based on chipless RFID technology, passive RFID technology, and ultra-high-frequency (UHF) RFID technology, including the implementation methods, as well as the advantages and disadvantages of those technologies. In addition, for RFID-based crack monitoring applications, the two most commonly used materials are concrete materials and metal materials, which are also illustrated in detail. In general, this study can provide technical support and a theoretical basis for crack monitoring and detection to ensure the safety of engineering structures.

Wireless Humidity Sensing with Chipless Radio Frequency Identification Tag

Wireless Humidity Sensing with Chipless Radio Frequency Identification Tag

Chipless RFID Tag Implementation and Machine-Learning Workflow for Robust Identification

In this work, we describe a complete step-by-step workflow to apply machine-learning (ML) classification for chipless radio-frequency identification (RFID) tag identification, covering: 1) the tag implementation criteria for circular ring resonator (CRR) and square ring resonator (SRR) arrays for ML interoperability; 2) the data collection procedure to get a sufficiently representative dataset of real measurements; 3) the ML techniques to visualize the data and reduce its dimensionality; 4) the evaluation of the ML classifier to ensure high-accuracy predictions on new measurements; and 5) a thresholding scheme to increase the certainty of the predictions. The differences in the tags’ frequency responses are maximized by optimizing the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Hamming distance</i> between the tag identifiers (IDs) and by controlling each resonator array’s radar cross section (RCS) level. We show that the proposed workflow achieves perfect accuracy for the identification of four tags at a fixed distance of 160 cm. We also evaluate the performance of the proposed workflow to identify up to 16 tags within a flexible range (up to 140 cm), showcasing the tradeoff between the number of tags that can be correctly classified based on the reading range.

Clutter Effect Investigation on Co-Polarized Chipless RFID Tags and Mitigation Using Cross-Polarized Tags, Analytical Model, Simulation, and Measurement.

Chipless radio frequency identification (RFID) technology is expected to replace barcode technology due to its ability to read in non-line-of-sight (NLOS) situations, long reading range, and low cost. Currently, there is extensive research being conducted on frequency-coded (FC) co-polarized radar cross-section (RCS)-based tags, which are widely used. However, detecting co-polarized chipless RFID tags in cluttered environments is still a challenge, as confirmed by measuring two co-polarized tags in front of a perfect metal reflector (30.5cm×22.5cm). To address this challenge, a realistic mathematical model for a chipless RFID system has been developed that takes into account the characteristics of the reader and the tag, as well as reflections from cluttered objects. This extensive mathematical model developed for linear chipless RFID systems in clutter scenarios holds the potential to greatly assist researchers in their exploration of RCS-based tags. By relying solely on simulations, this model provides a tool to effectively analyze and understand RCS-based tags, ultimately simplifying the process of generating more authentic tag designs. This model has been simulated and verified with measurement results by placing a single flat metal reflector behind two co-polarized one-bit designs: a dipole array tag and a square patch tag. The results showed that the interfering signal completely overlaps the ID of the co-polarized tag, severely limiting its detectability. To solve this issue, the proposed solution involves reading the tag in cross-polarization mode by etching a diagonal slot in the square patch tag. This proposed tag provides high immunity to the environment and can be detected in front of both dielectric and metallic objects.

A Quarter-Circled Multi-Resonator for UWB Re-transmission Based Chipless RFID

This paper introduces the design and analyses of a new planar parallel microstrip quarter-circled multi-resonator (PQMR) for the chipless radio frequency identification (CRFID) that works in ultra-wide band (UWB) frequency region. The proposed PQMR has identifying (IDing) and potential sensing capabilities to work as a tag-sensor. The PQMR works within 3.30 GHz – 6.53 GHz with a high -10dB quality-factor (Q10dB) of 692, a good spatial density of as low as 7.05 mm2/bit, very good spectral density of 7.33 bits/GHz and a coding capacity of 17 bit with one-bit sensing ability. Different combinations of coding bit streams are also extracted to show the identification ability of the proposed design. This will motivate the CRFID designers to design small and high-capacity tag- sensors for UWB applications.

A highly sensitive paper-based chipless RFID humidity sensor based on graphene oxide

In this paper, a highly sensitive paper-based humidity sensor is designed and fabricated to overcome the typically low sensitivity and small quality factor of paper-based chipless radio-frequency identification (RFID) humidity sensors. A toroidal inductor-interdigitated electrodes (IDE) capacitor is used as the resonator structure of the new sensor, and the structural parameters of the sensor are optimized using the software of high frequency structure simulator (HFSS) to improve the quality factor. Three paper-based sensor samples were fabricated via screen printing using regular printing paper, Kodak photo paper, and double-sided copper-coated paper as the substrate. In addition, the resonance characteristics, sensitivity, recovery characteristics, stability and other sensor performances were tested. The results show that the sensitivity of the copper-coated-paper-based sensor is significantly better than the two other paper-based sensors. The simulation and test results of the moisture-sensitive characteristics are consistent for graphene oxide (GO) films, which were prepared using the spray method on the surface of the copper-coated-paper-based sensor with mass concentrations of 1 mg/mL, 2 mg/mL, and 5 mg/mL. This indicates that GO films can significantly improve sensor sensitivity when combined with paper-based moisture sensing. Furthermore, the sensitivity increases with increasing GO concentration, the 5 mg/mL GO sensor show a sensitivity of 6.25 MHz/%RH and a range of 60% RH-90% RH. The 1 mg/mL GO humidity sensor shows good recovery characteristics (92.4% recovery). Based on the presence of hydrophilic functional groups in the GO material, a moisture sensing mechanism that GO could improve the sensitivity of the sensor is analyzed.

Novel flexible chipless RFID tags based on five state resonators

In this paper, novel chipless radio frequency identification (RFID) tags are designed by using asymmetrical triple mode resonators constructed by an open loop resonator with two open stubs in different lengths. Three transmission zeros (bits) can be obtained by coupling a proposed resonator to a straight feeding line that connects input/output ports. Five frequency codes can be achieved with respect to the existence of the open stubs and the open loop resonator. By coupling eight asymmetrical triple mode resonators to the feeding line, a multi-resonant circuit is developed on a flexible substrate of Rogers 5870. Totally 24 bit frequencies can be achieved and it is possible to identify 58 different items. For the chipless RFID tags, two monopole wideband antennas in vertical/horizontal polarizations are integrated instead of the input/output ports. Two tags have been fabricated and tested to demonstrate the identification of different codes under smoothed and curved positions successfully.

Comprehensive Review on Multiresonator-Based Chipless RFID Tag

This study reviews the multi-resonator-based chipless radio frequency identification technology. Radiofrequency (RF) waves are used in a wireless data collecting technique called radio frequency identification or simply RFID to automatically identify things. RFID is a promising technology that enables the identification and tracking of objects. Because of its benefits, including cheaper cost, smaller size, and higher security, chipless Radio Frequency Identification (RFID) technology has become more and more attractive as a potential alternative to traditional RFID technology. Chipless RFID labels are minimal expense labels since they are not outfitted with ASIC. RFID transmits data between the RFID transponder, a device that carries data, and the interrogator using radio frequency (RF) waves. The system is completely passive and does not require any kind of outside power source to run. The major advantage of spectral signature-based chipless RFID is that it can encode data in both magnitude and phase. A transponder's essential parts are its transmitter, receiver, and multi-resonators. As a result, this article will evaluate different multi-resonator types, explore numerous chipless RFID applications, and discuss the basic operation of an RFID system. Additionally, this research studies the various coding systems because information coding is an essential part of this technology.

Robustness Improvement for Chipless RFID Reading Using Polarization Separation

In this article, a novel method to improve the readability of chipless tags is presented. When the EM wave falls upon the tag’s surface at normal incidence or with a known incidence, the proposed approach permits to obtain a higher signal-to-noise ratio (SNR) of resonators whose orientation with respect to the normal to the plane in which the tag is positioned is unknown and, thus, to increase the reading distance of the tag. It introduces a technique based on the detection of this tag orientation in relation to the antennas; a projection of the signals will allow correcting this misalignment in order to always be able to decode the tag identifier on a signal that corresponds to an ideal alignment between the tag and the antennas. With this principle, it is also possible to separate the resonance mode of the resonator that is connected to the identifier from other parasitic resonance modes that may appear due to a possible misalignment between the tag and the antenna. This principle is applied to loop resonators commonly used in chipless radio frequency identification (RFID), which can present strong parasitic modes of resonance. Also, this method makes the reading orientation invariant, allowing to read the resonator whatever its orientation with respect to the normal to the plane in which the tag is positioned. Likewise, the proposed method can be also used to sense this resonator orientation. This method requires a dual-polarization antenna and a two-port vector network analyzer (VNA). Results are validated in simulation and with real-environment measurements for a single resonator and multiple resonators, as it is classically used in chipless RFID technology. Measurements in a harsh environment, as well as comparisons with classical techniques, such as time gating (TG), are presented. A study on the improvement of the read range is achieved to highlight the potential of the proposed technique. A reading distance of more than 80 cm was, thus, obtained, which represents 20 cm more than with the classic use of a postprocessor based on time gating. Finally, the principle of the measurement is generalized by applying it to a tag with a ground plane and considering that the antenna is not necessarily placed in normal incidence with respect to the plane of the tag.

From Chip-Based to Chipless RFID Sensors: A Review

Radio Frequency Identification (RFID) sensors have received increasing attention in recent years due their wireless battery-free operation, low-profile, simplicity, low-cost, and multimodality sensitivity. They have found their way to everyday applications including smart packaging for food quality assurance, early noxious gas detection, smart bandages for chronic wound assessment, and structural health monitoring. This work aims to provide a review of chip-based and chipless RFID sensor technology and to depict a transition from the former to the later one. This is conducted by highlighting existing challenges for implementation of chipless RFIDs, possible solutions to overcome these problems, and recent development introduced in the literature. Then, it has been demonstrated how RFID sensors in conjunction with artificial intelligence and machine learning can be applied for enhancing RFID tag sensitivity and selectivity to a high degree of accuracy. The focus of this paper is on chipless RFID sensors, and at the end the authors present a direction for future research work.

Chipless RFID Sensors for IoT Sensing and Potential Applications in Underground Mining—A Review

Chipless radio frequency identification (RFID) sensors have enormous potential for underground mining applications since this technology has the potential to meet all the requirements, such as wireless communication, maintenance-free, long lifespan, and battery-free, required to deploy in harsh underground environments. This paper has analysed existing frequency domain chipless RFID sensor technologies to understand suitability for potential applications, such as environmental condition monitoring, support system stability detection, and health monitoring of mining structures in underground mining sites. In light of the analysis, the paper has presented a new classification based on sensing materials and intrinsic sensing parameters such as effective length, coupling, conductivity and permittivity. Furthermore, the analysis has considered accuracy, performance and readability using 3D Electromagnetic (EM) analysis software, CST Studio Suite. Finally, based on our critical analysis and experimental simulations, the paper has identified challenges that need to be addressed by future research for chipless RFID sensors in the underground mining application domain.

A Multibranch U-Shaped Tunable Encoding Chipless RFID Strain Sensor for IoT Sensing System

Structural health monitoring (SHM) is essential for modern large buildings and infrastructure. Radio frequency identification (RFID) widen a new paradigm for SHM in the Internet of Things (IoT) era. This article introduces a low-cost intelligent RFID monitoring system for future IoT applications. Through adding a multiparameter sensing strategy to the passive RFID tags that can be deployed on a large scale to form a sensor network, which expands the coverage of IoT in key positions health monitoring of buildings. In this work, a novel chipless RFID strain sensing tag is designed to characterize the magnitude and direction of metal surface strain, and a low-cost detection method suitable for large mechanical structures is proposed. The traditional strain antennas focus on identifying the strain characteristics without the function of encoding, and there are limitations, such as the rigid measurement methods and the expensive measurement instruments. The tag designed in this article integrates both strain sensing and encoding functions, and has the advantages of small size, high data capacity, and information reading is not easily affected by environmental noise. This article proposes an economical and flexible tag spectrum extraction method, which realizes the intelligent collection and transmission of tag data by connecting lightweight vector network analyzer (VNA) with microcontroller. Combined with the IoT, this method can be well applied to the security assessment and damage detection of large infrastructure structures, which provides a new approach to modern building health monitoring applications from integrated tag design to intelligent detection and risk assessment schemes.

Design of a metamaterial chipless RFID sensor tag for high temperature

A high temperature sensor based on a metamaterial is proposed as a chipless radio frequency identification sensor tag that can measure temperature wirelessly. The metamaterial, based on a double circular split ring resonator (SRR), is highly frequency selective and has negative permittivity. The double circular SRR is fabricated on the alumina ceramic substrate, which acted as the temperature sensing material. The permittivity of the material varies with the temperature parameter, resulting in a shift of backscattered resonant frequency of the sensor tag. Simulations verify the feasibility of this sensor tag in the microwave band under electromagnetic stimuli. When the temperature increases from 200 to 1000 °C, the resonant frequency monotone decreases from 6.64 to 6.26 GHz with an average sensitivity of 0.475 MHz/°C. The sensor tag has features such as high temperature, being wireless, passive, of comparatively low-cost, and miniature, with diversified application potential, allowing it to compete with other sophisticated temperature devices in terms of performance.

Electromagnetic Modeling Strategy Supporting the Fabrication of Inkjet-Printed Chipless RFID Sensors

Inkjet printing fabrication techniques can be used for the manufacturing process of chipless radio-frequency identification RFID sensors. With respect to traditional silicon-based fabrication, flexible electronics induce the possibility to experiment new substrates and conductive materials. With the development of high-conductive nano-inks the low sintering temperature required to process them results compatible with a large variety of substrates. However, the requirements for the conductivity of the metallized printed patterns are particularly stringent for applications where the working frequency is high, like in the case of common chipless RFID tags working in the frequency range 3-10GHz. In chipless RFID systems, the higher the conductivity of the conductive parts and the better the signal response of the tag. However, in printed chipless RFIDs the conductivity can only give a partial indication of the goodness of the tag. The tag response is dependent on the sheet resistance, which is not only related to the conductivity of the ink but also to the thickness of the printed pattern. Therefore, if a sufficiently high-conductive nano-ink is selected, the signal efficiency of the printed tag can be further improved by making an evaluation based on the thickness of the patterns. The objective of this study is to propose a strategy for evaluating the signal response efficiency in inkjet-printed chipless tags by means of a first quantification of the average thickness of the printed layer, which is used to feed a finite element method simulation model to give the manufacturer an idea of the optimal number of layers to be printed in order to have a strong signal response.

A Novel Multiresonant Chipless RFID Tag for Directional Strain Measurement on Metal Surface

In this article, a radio frequency identification (RFID) sensor tag for real-time health monitoring of the magnitude and direction of metal surface strain is presented. The chipless RFID sensor tag is composed of metal foil and F4B substrate, which is low-cost and works stably in harsh environments for a long time. Through highly sensitive strain monitoring, the risk can be predicted in the early stage of defect generation. The proposed tag includes a C-type resonator array, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> -type transmission line, and tag antennas. The C-type resonator has different sensitivities in the electrical length direction and width direction. Then, based on this characteristic, the resonator array creates a plurality of characteristic signatures containing strain information by optimizing the geometric parameters of the resonators. The strain information is transmitted to the tag antenna through the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> -type transmission line to complete the wireless communication between the tag and the reader. Finally, the performance of the strain monitoring system is verified by an experimental study. The experiment shows that the average sensitivity of the resonators is −4.94 and 1.14 kHz/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula> in the electric length and width directions, respectively. When the strain is more than 150 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula> , the relative error of magnitude is less than 12.7% and the absolute error of direction is less than 13.3°. Therefore, the proposed chipless RFID tag can monitor the amplitude and direction of strain with higher sensitivity and a simpler structure, for the key structures, such as the high-speed running gear.

A Fully Passive Ten-Digit Numeric Keypad Sensor Using Chipless RFID Technology

A ten-digit chipless radio frequency identification (CRFID)-based numeric keypad that works on the principle of touch event sensing is presented. The tag is designed to operate using the passive frequency-domain (FD) technique. The proposed tag has ten circular resonator rings for each of the keypad’s corresponding decimal digits. Each circular ring resonates at a particular frequency within the 400-MHz band from 2.7 to 7.6 GHz to uniquely identify a digit. Identification is performed by decoding radar cross Section (RCS) response of the whole keypad tag. A customized human finger using standard tissue characteristics is modeled to verify the keypad’s working mechanism. When the finger is placed on any of the nine resonators, its corresponding resonance disappears from the allocated band. The proposed CRFID keypad sensor tag is built upon a Rogers substrate of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$85\times 95\times0.8$ </tex-math></inline-formula> mm volume. The backside of the proposed tag is fully copper filled for an easy interface with a variety of backgrounds, including metallic walls. The design exactly mimics the shape of ordinary keypad. The finger model used in the simulations realizes the practical scenario. This CRFID keypad is deemed an intriguing solution for future automated cities and will help in the conceptualization of Internet of Things (IoT) systems.