Chipless Radio Frequency Identification Tag Research Articles

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.

Wireless Humidity Sensing with Chipless Radio Frequency Identification Tag

Wireless Humidity Sensing with Chipless Radio Frequency Identification Tag

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.

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.

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.

Design of A 20-Bit Chipless RFID Tag Utilizing Multiple Resonators in UWB Frequency Range

Radio frequency identification (RFID) is a growing technology for monitoring and recognizing objects, persons, or animals via wireless communications. Precisely, RFID can operate longer range and has an ability to be automated without human control. Chipless RFID tag basically is a RFID tag that does not require a microchip in the transponder. The major impediments in designing chipless RFID tag are data encoding and transmission. The passive chipless RFID tag can be fabricated on any substrate material without external operating circuit, which is different compared to a conventional chipped RFID tag. In this paper, 20 resonators are used to design a 20-bit chipless RFID tag, which operates at the ultra-wideband (UWB) frequency range between 3.00 and 10.00 GHz. It is found that the additional resonators can encode data and increase the chipless RFID tag's encoding capacity significantly. In sum, multiple resonators enable the chipless RFID tag to encode data at different operating frequencies.

A Semi-Octagonal 40-Bit High Capacity Chipless RFID Tag for Future Product Identification

This paper presents a unique geometry of a chipless radio frequency identification (RFID) tag for encoding a large number of bits in a very small form factor. The tag geometry consists of semi-octagonal copper strips, sequentially laid on a single side of an ultra-thin substrate. A unique and robust encoding mechanism for the tag identification (ID) is proposed. The operating frequency spectrum of the tag ranges from 3.1 to 10.5 GHz. The tag is compact, having an overall size of 14.5 × 28 mm2. The proposed tag exhibits very high code density of 9.85 bits/cm2 and spectral efficiency of 5.4 bits/GHz. The unique geometric configuration of the proposed tag allows it to encode up to 40 bits of data as an RCS signature. This chipless RFID tag seems to be a potential candidate for a wide range of modern RFID applications.

A Novel Design Methodology to Realize a Single Byte Chipless RFID Tag by Loading a Square Open-Loop Resonator With Micro-Metallic Cells

In this paper, a unique structural design methodology for chipless radio-frequency identification (RFID) tags in frequency domain is presented. The tag geometry is developed by loading an open-loop resonator with micro-metallic-cells (MMC). The realization give rise to a checkerboard resonator type with electromagnetic signatures in its radar cross section that are extremely efficient to manipulate. The resonators layout is distributed on either side of a Rogers substrate to double its coding density. The proposed chipless RFID tag has a memory of 8-bits in total. The operating band of the tag is 6.5-10.5 GHz. The tag has a high bit coding density of 10.94 bits/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and spectral efficiency of 2 bits/GHz. The tag has a very compact size of 17.4 × 4.2 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The simple structuring methodology and efficient resonators layout will give RFID system designers the flexibility to apply the proposed tag in a wide range of modern applications.

Development of low-profile spectral signature chipless flexible RFID prototype for 5G supply chain IoT applications

A novel spectral signature Chipless Radio Frequency Identification (RFID) tag is designed, fabricated, and validated as a barcode replacement for Fifth Generation (5G) supply chain-based Internet of Things (IoT) scenarios. The tag displays a low profile of 12.7 × 13.9 mm2 with radiating data capacity of 32 bits. The design includes a hybrid On-Off and frequency shift keying technique to enhance the data encoding functionality. The unit tag translates 1:1 slot-to-bit by integrating an open stub L structure as a resonating assembly. Further, hybrid encoding has been incorporated to enhance the ratio up to 1:3, which leads to a 3n(2n-1) data pattern. As a result, the Chipless RFID tag offers a noticeable density per frequency of 4.6 bits/GHz for a 3.1–10.9 GHz spectral variation. The design is carried out over a flexible substrate, Taconic TLX-0, and the results exhibit fair agreement between simulated and measured results. Further, tag performance is validated by placing it on different objects: books, silver cups, and wooden boxes.

A Miniaturized Dual-Resonator-Based High-Capacity Chipless Radio Frequency Identification Tag Sensor

The chipless radio-frequency identification (RFID) sensor is a potential technology for future RFID-based sensing systems. A novel ultra-wideband and retransmission-method-based frequency-coded chipless RFID tag is presented in this letter. The footprint of the proposed RFID tag is reduced by incorporating spur-line spiral resonators along with the spiral resonators. These resonators are designed within and around the transmission line connecting two orthogonal ports of the dual-polarized monopole antenna operating in the transceiver mode. Initially, the patch antenna and the resonator circuits are optimized separately for the intended impedance bandwidth and frequency response, respectively, and are later integrated together to achieve the required performance. The operating range of the tag antenna is from 2 to 5.2 GHz. Furthermore, two prototypes of the proposed RFID tag with the 10-b code are fabricated and tested. The simulation and experimental results are found to be in good agreement, validating the proposed design.

Detecting Breaks in Cold Chain Integrity Using Chipless RFID Time–Temperature Sensors

This article presents a low-cost, food-safe chipless radio-frequency identification (RFID) time–temperature (TT) sensor that operates in the 3–5 GHz [ultra wide band (UWB)] band. The sensor is capable of detecting three types of TT exposure events typically found in cold chain operations. We achieve this by interfacing a chipless RFID tag with three cooking oils having melting points of 14.2 °C, 17.3 °C, and 23.6 °C, respectively. The three TT events induce unique changes in the oil phase (solid to liquid) for all three oil types and this manifests as distinct signal responses from the chipless RFID tag. We discuss how logistic providers can infer TT exposure data at key steps in the cold chain via quantitative data obtained from these responses. Planned sensor improvements and future research directions are also discussed.

Patterned Ag/PI RFID Tag Integrated with Humidity Sensing by In Situ Metallization.

This article presents a cost-efficient flexible chipless radio frequency identification (RFID) tag with wireless humidity sensing, which is fabricated by in situ metallization and inkjet printing techniques. The inkjet printing technique is applied to print the mask for RFID antenna, which is designed with frequency-encoding simulation by a high-frequency structure simulator (HFSS). A high-quality patterned Ag antenna is realized by the in situ metallization of a polyimide (PI) film, leading to strong adhesion between the Ag antenna and PI substrate. The patterned Ag antenna of the chipless RFID tag consists three parallel dipole resonators, one of which is sensitive to humidity, while the other two are utilized to encode and store data. As a result, a 2-bit chipless RFID with high humidity sensitivity based on a Ag/PI film is developed, which displays excellent flexibility and good mechanical stability. The performance of the fabricated tag shows good agreement with the simulation results. Moreover, the tag is applied to detect the water source, where the resonance frequency shows good linearity versus the distance to the water source. These results demonstrate that the proposed chipless RFID tag with humidity sensing has a 2-bit storage capacity, high humidity sensitivity, excellent mechanical properties, and long-term stability, confirming a cost-efficient preparation process for flexible electronics.

Physical-Layer Detection and Security of Printed Chipless RFID Tag for Internet of Things Applications

This article has proposed detection and physical-layer security provision for printed sensory tag systems for Internet of Things (IoT) applications. The printed sensory tags can be a very cost-effective way to speed up the proliferation of the intelligent world of IoT. The printed radio-frequency identification (RFID) of a sensory tag is chipless with the fully printable feature, Nonline-of-Sight (NLoS) reading, low cost, and robustness to the environment. The detection and adoption of security features for such tags in a robust environment are still challenging. This article initially presents a robust technology for detecting tags using both the amplitude and phase information of the frequency signature. After successfully identifying tag IDs, the article presents novel physical-layer security using a deep learning model to prevent the cloning of tags. Our experiment shows that the proposed system can detect and identify the unique physical attributes of the tag and isolate the clone tag from the genuine tag. It is believed that such real-time and precise detection and security features bring this technology closer to commercialization for IoT applications.

Frequency-Coded and Programmable Synchronous Electromagnetic Encoders Based on Linear Strips

This letter presents electromagnetic encoders where encoding is achieved by considering four different inclusions, particularly linear strips of different length, etched at the predefined positions of the encoder chain, and transversely oriented with regard to the chain axis. Since the length of the strips determines their resonance frequencies, it follows that the 2-bits per inclusion, corresponding to the four possible different states (strip lengths), are frequency-coded. Thus, the reader is a microstrip line with a series gap fed by four harmonic (carrier) signals tuned to the resonance frequencies of the four considered encoder strips. By encoder motion over the reader, each carrier signal is amplitude modulated, with envelope functions exhibiting a peak each time a strip of the encoder chain tuned to the resonance frequency of the considered carrier signal crosses the axis of the reader line. The functionality of the system is experimentally validated in this letter. It is also shown that the encoders can be programmed by considering identical strips and by cutting them appropriately, according to the desired code. The proposed encoders are intrinsically synchronous. Such encoders are useful for measuring displacements and velocities, as well as for the implementation of synchronous near-field chipless radiofrequency identification tags with sequential bit reading.

High capacity chipless RFID tags for biomass tracking application

AbstractThe design of a low-cost, flexible, miniaturized, and a high code density chipless radio-frequency identification (RFID) tag is presented as a solution for tracking the transportation of biomass fuel pellets. The performance of the tag is presented and demonstrates the applicability of the design for different material systems, while maintaining a compact size of 5.06 cm2. The tag consists of nested concentric hexagonal elements and a central spiral resonator suitable for ID encoding. The tag presented demonstrates code density of 3.6-bits/cm2, possesses angular stability up to 60°, and high radar cross section (RCS). The tag performance was also observed for tracking 5 kg of fly-ash biomass. Additionally, as the tag mass mostly consists of FR4, PET, or Taconic TLX-0 with a minute mass of either copper, gold, or silver, the tag can be easily combusted and disposed of during biomass combustion. The novel features of this tag are the combination of hexagonal and spiral shape slots for maximum space utilization thereby achieving high RCS signatures along with high code density. All these properties of the proposed chipless RFID tag provide a pioneering pathway for a real-time biomass tracking application.

Depolarizing Chipless RFID Tag Made Orientation Insensitive by Using Ground Plane Interaction

The ground plane has never been considered as a degree of freedom to be used for chipless radio frequency (RF) identification (RFID) tag design purposes. For the first time, we show that the interaction with the ground plane can be exploited to achieve challenging designs, such as depolarizing tag insensitive to orientation (i.e., nonzero cross polar for any roll angle). The principle relies on the perturbation of the ground plane symmetry with merely one microstrip dipole placed near the edge of the substrate. Chipless RFID tags are realized using three different shapes of the substrate (square, octagonal, and circular) to achieve multiple edges. The measurements are performed in a semianechoic and office environment with tag attached to objects (cardboard box and metallic plate). The measured results of the square chipless RFID tags present magnitude variations (< 10 dB) but are detectable over a full 360° even in real environment yielding an “orientation-insensitive” detection system. Compared to previous designs, the frequency variability of the peaks is negligible.

High Data Capacity Chipless RFID Tag Based on Time-Domain Scattering Modulation

In this communication, we present a low-cost chipless radio frequency identification (RFID) tag with a high data capacity and a wide reading range based on time-domain scattering modulation. The proposed tag consists of a slotted square patch antenna with a switchable resistor and a mechanically driven slider etched with a barcode-like metallic wire array. Encoding is achieved by the presence and absence of the metallic wire on the slider, and tag identification is obtained by sequential bit reading. A special encoding strategy is applied to improve its insensitivity to the motion velocity of the slider. For a proof-of-concept demonstration, a prototype designed to operate at 2.1 GHz was fabricated and measured, and the experimental results verified the effectiveness. Compared with the methods based on time-domain reflectometry, spectral signature, and resonator-based sequential encoding, the proposed approach provides a substantially enhanced data capacity within a narrow spectrum without sacrificing its reading range and tag size, due to the design of nonresonant code cell. Such a mechanically triggered chipless RFID tag exhibits promising potentials in some practical applications, such as personal ID and credit cards.

Data dense chipless RFID tag with efficient band utilization

One of the critical challenges in deploying radio frequency identification (RFID) is its cost of production. An approach to mitigate and be cost-effective is to design chipless, inexpensive electronic tags having a smaller size. Therefore, in this paper, a novel 22-bit passive chipless RFID tag with an enhanced radar cross-section (RCS) response is proposed. The tag design is loaded with ‘U’ and ‘Inverted-U’ shaped slots. The ‘U’ and ‘Inverted-U’ slots are etched on a metallic plate of size 39x40 mm2 for 22-bit data capacity and the tag can label 222 = 4,194,304 objects. The final tag design is optimized for Taconic TLX-0 and RT/duroid®5880 substrates. Each 'U' and 'Inverted-U' shaped loaded slot are of different lengths and thus yield resonance at a particular frequency. The presence of a dip corresponds to the '1′ bit and the '0′ bit is achieved in the data word by shortening the particular slot. A detuning correction scheme is proposed by placing the slots in a special arrangement. By opting for this approach not only the tag exhibits an improved RCS response but also, the effect of shorted slot representing '0′ on the neighboring dip is reduced. The proposed RFID tag can be deployed in tracking inventory, logistics, and low-cost business applications.