Chipless Radio Frequency Identification System Research Articles

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.

System Development of Calibration-Free 20.7-Bit Chipless RFID Without Iterative Optimization of Tag Configurations

Earlier studies have improved the data capacity of frequency-coded chipless radiofrequency identification (RFID) to 100 bits, but these high-density tags may suffer from two limitations, including the design complexity for billions of tags and an additional procedure for measuring clutter. In this paper, a calibration-free chipless RFID system with 20.7-bit capacity is proposed; moreover, the design of the 1.68 million tags is highly efficient, preventing individual and iterative optimization for such large numbers of configurations. These distinct features are obtained by integrating the signal processing of reader and the resonance synthesis of tags. The signal processing employs short-time Fourier transform (STFT) and enhanced filtering to achieve calibration-free detection. The resonance synthesis features minimized numbers of geometric parameters, reduced mutual coupling between resonators, and response surface models for the resonant frequency to realize noniterative optimization. The proposed system is validated by three approaches. First, residual plots indicate that the range of residuals is confined to the average bandwidth of frequency slots. Second, 36 IDs are sampled and automatically transformed into chipless tags. The measured reliability of four bands is as high as 100%, 95.0%, 98.3%, and 93.9%, respectively. Finally, the parameterization of signal processing is validated by time-frequency analysis and reliability.

Classical RFID Versus Chipless RFID Read Range: Is Linearity a Friend or a Foe?

This article presents a comparison between the read range of classical radio frequency identification (RFID) and chipless RFID in free-space and real environments (REs). From the presented model, read range is derived using analytical formulation over nonisolated channels for both technologies. This article shows that the well-known bounds classically used in free space cannot be achieved in REs, i.e., subjected to leakage, coupling, and/or reflections) and therefore need to be modified. Although the introduced bound for semipassive tags is close to the one corresponding to free space, however, we show that for chipless tags, read range cannot be predicted by the radar equation and presents severe limitations since these tags are linear time-invariant systems. This new bound does not depend on the transmitted power or the reader sensitivity but relies on the concept of residual environment. We show that this quantity is the key parameter to evaluate the read range of a chipless RFID system. Moreover, the residual environment can easily be estimated or measured for any reading system. We show that the proposed bound can accurately predict the read range of a chipless system in different environments from anechoic chamber to nonstationary REs. Results are confirmed in simulation and measurements where the difference between the theoretical read range and the measured one is only 20 cm.

Time and Frequency Domains Analysis of Chipless RFID Back-Scattered Tag Reflection

Chipless radio frequency identification (RFID) is a wireless technology that has the potential for many industrial applications, including the internet of things (IoT) applications, in which identification, sensing, and tracking are required. This technology has been improved during the last century. However, the processing of the backscattered signal in a chipless RFID system is still a challenge because the encoded data are embedded in the backscattered signal of a passive tag. The reader hardware, antennas, and the wireless channel have their own response in the received signal, which contains the tag ID information. The tag also produces a response, which is a combination of responses from different resonators, substrate, and copper reflection in a tag. In this paper, the reflection from a typical chipless RFID tag is analyzed, and all components of the backscattered signal are separated in both time and frequency domains. In addition, an equivalent circuit model for a backscattered chipless RFID tag is proposed, and the model is verified based on the actual performance of the resonator. This study has some important implications for future research.

Using Punctured Convolution Coding (PCC) for Error Correction in Chipless RFID Tag Measurement

This letter presents an error correction technique for chipless radio frequency identification (RFID) tags using punctured convolution coding (PCC). We use a frequency signature-based chipless RFID tag which can encode Tag IDs at different resonance frequencies. Due to the presence of unwanted interference during communication, the backscatter tag response undergoes an abrupt change in amplitude and a shift in frequency, resulting in missing bits or errors. Normally, error correction in RFID technology requires intelligent behavior on the tag and in the reader. Our proposed measurement technique abandons the need for an integrated circuit (IC) and memory on the tag. Alternatively, the error correction functionality is executed during the design and fabrication process in chipless RFID tags. The PCC-based chipless RFID tag is then detected by the detection technique based on the presence of tag resonance resembling logic “1” and “0,” which is then decoded using Viterbi decoder to obtain the original source data. The proposed technique can detect error and recover missing bits in the chipless RFID system.

A Comparative Survey on Silicon Based and Surface Acoustic Wave (SAW)-Based RFID Tags: Potentials, Challenges, and Future Directions

Many Automatic Identification (Auto-ID) technologies such as bar codes, magnetic stripes, Optical Character Recognition (OCR) and Electronic Article Surveillance (EAS) security tags are in existence. However, they are limited by a variety of constraints on them such as limited object rate of scan, need for Line-of-Sight (LOS) operation, very small interrogation range and poor accuracy in complex environments. Research has accordingly grown rapidly in recent years into the development of robust identification or tracking mechanisms. Radio Frequency Identification (RFID) technology using readers and RFID tags, whether passive, semi-passive or active in nature, has been deemed to be a promising candidate. Silicon based IC tags are quite popular. However, some alternative RFID technologies have also been on the rise. In particular, another special type of tag based on Surface Acoustic Wave (SAW) design also has a great potential for deployment in future identification fields due to its ruggedness against harsh conditions, metallic environments, interference, small and low cost and is being thoroughly reviewed, which is ignored in other survey papers. While other chipless RFID systems based on conductive ink, ink-tattoo and others do exist, negative aspects such as inability to survive in extreme weather, larger tag size and limited data storage capacity have severely impacted the penetration of such tags in the RFID market. Therefore, the scope of this survey article does not include chipless RFID tags. This article instead provides a comparative survey of silicon based IC and SAW based tags, which has attracted much attention from both academia and industry. The underlying characteristics, principles, advantages, and limitations of such tags are thoroughly discussed, and relevant research work followed by frequency of operation and other parameters are elaborated. This article undertakes a thorough investigation into the evolution of RFID technology and comparison into the current trend in silicon based IC and SAW based RFID tags and provides a comparison across many metrics, such as read range, tag size, tag power, availability of tag power, lifespan and more importantly, cost and security. It discusses active and passive tags under silicon based IC and SAW technology. Finally, the article reviews recent advances and provides potentials, open challenges and future research directions in such RFID tags. © 2013 IEEE.

Multiresonant Chipless RFID Array System for Coating Defect Detection and Corrosion Prediction

In this article, a fully passive, wireless solution for out-of-sight pipeline monitoring is presented. By predicting corrosion before its occurrence, a proactive response may be taken to mitigate the chance of an environmental disaster. The chipless radio-frequency identification system is a combination of a tag ID, consisting of an array of six rectangular spiral resonators, and a tag antenna consisting of two cross-polarized novel patch antennas etched on a skin-thin microwave laminate. The tags are grounded on a carbon steel pipeline coated with $\text{3 mm}$ Teflon (polyethylene-like electrical characteristics). The proposed system exhibits robust capability to create frequency signatures to detect and monitor defects underneath the pipeline coating owing to water ingress that could eventuate to corrode the pipeline. The reader antenna above the pipeline comprises two identically cross-polarized log periodic dipole antennas with the intent to remotely capture resonances of the tag ID in real-time for early detection and prediction of potential pipeline exposure to moisture. The proposed structure provides low-cost real-time solution.

A high capacity tunable retransmission type frequency coded chipless radio frequency identification system

This article presents a 12-bit frequency coded chipless RFID system in the frequency range of 3 to 6 GHz. The system consists of a fully printable chipless tag and a pair of high-gain reader antennas. The tag also incorporates its own antennas to improve the read range. Information is encoded into frequency spectrum using a multi-resonant circuit. The circuit consists of multiple microstrip U and L-shaped open stub resonators patterned in a unique configuration. The proposed configuration aids in capturing more data in a reduced space as well as tunable frequency operation. Tag and reader antennas utilize techniques such as stepped impedance feeding line, defective partial ground plane, and stair-step patch structure to achieve wide-band impedance bandwidth in miniature size. The results of the wireless measurements in the non-anechoic environment show that the proposed system has a reading range of more than 20 cm. The presented system possesses great potential for low-cost short-range inventory tracking.

Analysis of real‐world implementation challenges of chipless RFID tag

Radio frequency identification (RFID) tags are highly sensitive to material contents of the tagged objects, especially with liquids and metals. The presence of an attached object on the tag can be detrimental for tagID detection. In this study, the RF performance of chipless RFID tag placed on different commercial objects for identification purpose is comprehensively analysed. Probable solutions are proposed for observed issues to make the chipless RFID tags readable on various items such as non-conductive objects, liquid containers and metal items. The misalignment between the reader antenna and the tag is another issue during the commercial implementation of chipless RFID system. A tri-planar positioning of the tag has been verified as an appropriate solution in this study. The chipless tag has the potential to read stacked pallets and boxes with liquid/solid contents in warehouse scenarios using the proposed solutions.

Spatial-Based Chipless RFID System

Conventional techniques in chipless radio frequency identification (RFID) systems are incapable of fully overcoming the key challenges of modern identification applications, including high data capacity, low tag cost, and reliable operation. The idea of electromagnetic imaging in chipless RFID systems is a promising technique that shows many advantages over other conventional approaches. This paper reviews conventional chipless RFID technology and provides a comprehensive analysis of advanced millimeter wave spatial-based (also known as image-based) chipless RFID systems with an optimized multiple-input multiple-output-synthetic aperture radar technique for high-resolution image acquisition and a quick reading process.

A Novel Detection Technique for a Chipless RFID System Using Quantile Regression

This work presents a novel approach for improving the detection capabilities of a chipless Radio Frequency Identification (RFID) system based on quantile regression. The main drawback of chipless RFID systems is the limited response of the tags due to the low-quality factor of the resonators, used to encode the information in the tag. The detection becomes very challenging especially for real-time data when noise is present. This work proposes the use of quantile regression to enhance the system performance. A chipless RFID system prototype has been fabricated (as a proof of concept) and experimentally assessed. The obtained results are quite satisfactory in the potentialities of the proposed methodology.

Long reading range for the frequency coded Chipless RFID system based on reflectarray antennas

AbstractThis work proposes the utilization of a high gain and pencil beam reflectarray (RA) antenna at the reader of the frequency coded (FC) chipless radio-frequency identification (RFID) system to minimize the environmental reflections and increase the reading range. Moreover, the reader antenna should operate over ultra wideband (UWB) range of frequencies to accommodate multiple bits. However, the conventional antenna arrays cannot operate over UWB range of frequencies with high gain and pencil beam characteristics. Therefore, a novel UWB RA antenna dedicated to the chipless RFID reader is developed. The developed RA antenna operates over UWB range of frequencies from 4 to 6GHzto fulfill the requirements of the FC chipless RFID system. Therefore, the antenna is successfully integrated with the FC chipless RFID tags, and a reading range of 1mis achieved.

High-Accuracy Indoor Localization Based on Chipless RFID Systems at THz Band

Highly accurate indoor localization based on significantly low complex infrastructure has recently gained great interest for a variety of innovative location-based applications. In this regards, the chipless radio frequency identification (RFID) system is presented to be the low-cost solution, while time-based ranging using the ultrawide-band spectrum is promising to offer precise ranging capability. However, the current wide-band systems suffer from the spectrum and power limitations, which restrict the function of chipless RFID-based localization systems. Therefore, we propose terahertz (THz)-based chipless RFID localization system that enables a smart object localizing itself using the infrastructure composed from reference chipless tags. In more details, THz band offers huge bandwidth providing superior-resolution localization and large coding capacity. Moreover, we utilize the combination between dielectric resonator (DR) and lens to be designed as a frequency-coded chipless tag, where this combination increases the radar cross section of the chipless tags and, hence, extends their coverage zone. This cost-efficient design of the tag enables the dense deployment of low-cost infrastructure acting as reference anchors. Furthermore, we investigate the link budget of the proposed system in order to characterize the tag and distance-dependent spectral windows that are feasible for RFID-based localization. Afterward, the time-domain backscattered signal from a DR-Lens tag is analyzed in order to perform ranging and to calculate the relative distances between the DR-Lens tags and the reader leading to determining the reader position. Measurements are performed to prove the concept of the DR-Lens tag, while the numerical simulation is conducted to evaluate the proposed localization system. Simulation results show that the proposed system can reach superior accuracy of millimeter-levels.

Adaptive spectrum scanning techniques for reducing the identification time of the frequency coded chipless RFID system

AbstractThe main objective of this contribution is to introduce novel techniques for reducing the time taken from the reader to identify the frequency coded chipless radio frequency identification tags existed in the reader's interrogation region, system latency. The frequency scanning methodology, number of averaging for clutter removal, and hop duration are the 3 main parameters that significantly affect the overall system latency. Consequently, the adaptive frequency hopping (AFH) and adaptive sliding window (ASW) methodologies are proposed and proofed to be efficient for the chipless radio frequency identification systems from the latency and accuracy perspectives. Likewise, the performance of the designed AFH and ASW techniques are compared with the classical fixed frequency hopping methodology with a fine frequency step to validate the accuracy of the proposed methods. Moreover, 4 different coded frequency coded chipless tags are manufactured and used in the measurements. A real‐world testbed is designed including a software‐defined radio platform by which the proposed adaptive algorithms and traditional fixed frequency hopping methodology are implemented. All the measurements are performed in an indoor realized scenario, including the environmental effects. The experiments show that the proposed AFH combined with ASW algorithms significantly reduce the system latency by 58%.

Optimized MIMO-SAR Technique for Fast EM-Imaging of Chipless RFID System

Spatial diversity cross-polar approach to fast electromagnetic imaging of millimeter-wave chipless radio-frequency identification (RFID) tags is proposed. Slow imaging in the synthetic aperture radar (SAR) technique due to the moving reader antenna is replaced by a stationary multiple-input multiple-output (MIMO) array antenna. The proposed MIMO technique requires a large number of antenna elements, which impedes practical implementation of the reader. An optimized MIMO system through a genetic algorithm halves the number of antenna elements and successfully replaces the conventional SAR. The optimized antenna system combines with the original spatial diversity approach to provide a low-cost solution for chipless RFID tagging with enhanced content capacity. The system successfully decodes a 60-GHz 17-b chipless tag in an area that is one fifth of a credit card. The tag can be printed with a low-resolution printer and read on metal and liquid containers.

Design and Analysis of Multi-Resonators Loaded Broadband Antipodal Tapered Slot Antenna for Chipless RFID Applications

Chipless radio frequency identification (RFID) technology recently observed a growing interest, mainly because of its wide area of applications, and huge potential market, with the advent of Internet of Things era. Recently, in the demonstration of high capacity chipless RFID tags, ultra-wide-band technology has been proposed. It can enable development of robust chipless RFID systems with the promising features of low cost, compact, and lightweight. In response, we propose a novel scheme of broadband chipless RFID tagging that is based on slot coupled tapered slot antenna (TSA) loaded with a set of resonators, referred to as multi-resonators filters (MRF). Using numerical simulations, out of 256 combinations, randomly selected 14 different 8-bit MRF circuits operating over the frequency band 4 to 9 GHz are designed and their spectral and time domain responses under short and open terminations are recorded. The time domain signatures, generated due to high impedance mismatches along the microstrip lines of MRFs terminated with open and short circuits, are quantified by finding the cross-correlation among the signals and that is done by calculating the pulse fidelity factor. The designed MRFs are integrated with TSA to develop chipless RFID tags, referred to as MRF-TSA tags. Our designed TSA operates over 3.5–18 GHz band with an average gain that exceeds 6.5 dBi. The retransmitted time domain signals from the MRF-TSA tags are modulated by loading the antenna with MRFs terminated with either short or open loads. The recorded time domain signals are reasonably distinguishable since 85% (96%) of fidelity factor values among the 14 different MRF-TSA tags with open/short termination are less than 0.70 (0.8), respectively. Finally, for verification purposes, two different MRF-TSA based chipless tags are designed and fabricated. RFID monostatic measurements based on the use of vector network analyzer are also reported.

Real‐world testbed for multi‐tag UWB chipless RFID system based on a novel collision avoidance MAC protocol

ABSTRACTChipless radio frequency identification (RFID) tags are dummy, memoryless, with limited number of bits, very low backscattered power, and short reading range. Therefore, the existing RFID standards and protocols designed for the chipped RFID systems are not applicable for the chipless systems. Main objective of this contribution is to introduce a novel real‐world testbed for multi‐tag ultra‐wideband (UWB) chipless RFID system. In this testbed, a new Notch Position Modulation scheme is implemented as the first medium access control algorithm for handling the multi‐tag identification scenario of the frequency signature based chipless RFID tags. This intelligent Notch Position Modulation algorithm reduces the sensing and identification time and accordingly the overall system latency. The proposed protocol enables fetching the frequency signatures of the chipless RFID tags through the whole UWB range effectively. Moreover, an advanced signaling scheme is designed for the RFID reader in order to make the best use of the Federal Communications Commission UWB regulations for increasing the maximum transmitted power and the corresponding reading range. The signaling scheme, real‐time channel estimation, and clutter removal technique are implemented on the software defined radio platform in a heavily dense multipath indoor environment. Based on the medium access control protocol, the mitigation of the undesired environmental reflections as well as the interference between the chipless RFID tags is well demonstrated in the developed testbed.

Potential and Practical Limits of Time-Domain Reflectometry Chipless RFID

This paper provides a fundamental analysis of the maximum possible information content and reading range of chipless time-domain reflectometry (TDR) radio frequency identification (RFID). Bits encoded on a tag as well as bits that can be decoded by the reader need to be considered to estimate the information content on a tag. This needs an approach that deals with the entire RFID system. Factors such as insertion loss, reader signal, reading range, and channel properties impact the number of bits that can be decoded by the reader. Taking these parameters into account on their own, we can model the signal properties at the decoder by equations from radar theory such as the Cramer-Rao lower bound. The overall performance of these systems cannot be satisfactorily described by the radar theory, as today’s chipless RFID systems use different modulation schemes to increase the information content. Modulation theory can provide a detailed analysis of the modulation schemes depending on the channel and signal properties. This theory influences the tag design and the demodulation algorithms on the decoder, but is not suited to describe the RFID systems as a whole. This paper provides an approach that combines the radar and modulation theories to provide an exhaustive description of chipless TDR RFID communication. The maximum information content obtainable in practice can be estimated with this analysis. The introduced methodology is applied to surface-acoustic wave and ultra-wideband delay-line-based TDR tags. We present the simulations and measurements taken with different tags to show the practical importance of the theoretical findings.

A novel phase coding method in chipless RFID systems

This paper presents a novel data encoding method for chipless radio frequency identification (RFID). Utilizing this method can reduce the required frequency bandwidth for data encoding in RFID tags. Accordingly, each frequency in the transmitted signal from the chipless tag can carry a code equal to a base-3 number. Higher utilization of the transmitted signal results in a lower frequency bandwidth requirement. The proposed method only uses the phase of transmitted signal for data encoding. Furthermore, simple encoding method, low cost, and capability of these structures to be printed on different dielectrics, makes it a suitable choice for mass production RFID applications.

IR-UWB-based chipless RFID system

This paper presents a chipless radio frequency identification (RFID) system, based on impulse radio ultra-wideband (IR-UWB) technology. This UWB-RFID system consists of a transmitter, a receiver, two tapered slot antennas, and several chipless tags. Covering the lower UWB frequency band in 3–5 GHz, the transmitter integrated circuit generates signals with high peak-to-peak amplitude of 6.6 V and short pulse duration of 1 ns. The receiver front end consists of amplifiers and filters, with total front-end gain up to 36 dB. This is followed by an equivalent time sampling analog to digital converter to sample the equivalent RF signals directly followed by digital signal processing in MATLAB. The tapered slot antenna has a high and relatively flat gain of 10 dBi. The chipless tag is uniplanar and with a size of 23 × 23 × 0.508 mm3 only. Based on these hardware designs developed in our research group, a novel method is proposed to separate two overlapped time-domain signals. This method, which is experimentally validated in this paper, greatly simplifies the hardware designs, especially the chipless tag. This chipless UWB-RFID system is an excellent candidate to realize a low-cost, low-power, and high-performance system for next-generation RFID applications.