Semi-passive Tags Research Articles

Planar Thermoelectric Microgenerators in Application to Power RFID Tags.

This paper presents an innovative approach to the integration of thermoelectric microgenerators (μTEGs) based on thick-film thermopiles of planar constantan-silver (CuNi-Ag) and calcium cobaltite oxide-silver (Ca3Co4O9-Ag) thick-film thermopiles with radio frequency identification (RFID) technology. The goal was to consider using the TEG for an active or semi-passive RFID tag. The proposed implementation would allow the communication distance to be increased or even operated without changing batteries. This article discusses the principles of planar thermoelectric microgenerators (μTEGs), focusing on their ability to convert the temperature difference into electrical energy. The concept of integration with active or semi-passive tags is presented, as well as the results of energy efficiency tests, considering various environmental conditions. On the basis of the measurements, the parameters of thermopiles consisting of more thermocouples were simulated to provide the required voltage and power for cooperation with RFID tags. The conclusions of the research indicate promising prospects for the integration of planar thermoelectric microgenerators with RFID technology, opening the way to more sustainable and efficient monitoring and identification systems. Our work provides the theoretical basis and practical experimental data for the further development and implementation of this innovative technology.

A construction accident prevention system based on the Internet of Things (IoT)

In recent years, emerging sensing and detection technologies have been adopted to enhance safety in many construction sites. In this paper, we proposed to use a radio frequency identification (RFID) system, which consists of RFID readers, semi-passive tags and an Internet of Things (IoT) network, to prevent accidents on construction sites. The proposed system with multiple functions is versatile for different situations. Firstly, it can effectively detect the entry/exit activities when workers carrying tags access a site. Such a record is essential in daily project management. Secondly, the system can be programmed to flexibly create various virtual zones of different sizes and shapes. The virtual zones are usually hazardous ones that anyone cannot approach and enter. The semi-passive tag will warn an intruder if someone intentionally or accidentally intrudes the zones. A warning message is generated and sent to the remote server in real-time via the IoT network. Lastly, by adopting the advanced LoRa technology in the IoT network, the sensed data can be wirelessly transmitted over a longer distance than other wireless technologies, such as WiFi and Bluetooth, thereby reducing the number of transmission hops and improving the transmission efficiency.

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.

Multi-Tag Backscattering to MIMO Reader: Channel Estimation and Throughput Fairness

Green low power networking with the least requirement of dedicated radio resources is need of the hour which has led to the upsurge of backscatter communication (BSC) technology. However, this inherent potential of BSC is challenged by hardware constraints of the underlying tags. We address this timely concern by investigating the practical efficacy of multiple-input-multiple-output (MIMO) technology in overcoming the fundamental limitations of BSC. Specifically, we first introduce a novel least-squares based channel estimation (CE) protocol for multi-tag BSC settings that takes care of both the unintended ambient reflections and the inability of tags in performing estimation by themselves. Then using it, a nontrivial low-complexity algorithm is proposed to obtain the optimal transceiver designs for the multiantenna reader to maximize the minimum value of the lower-bounded backscattered throughput among the single-antenna semi-passive tags. Additional analytical insights on both individually and jointly-optimal precoding vector and detector matrix at the reader are provided by exploring the asymptotically-optimal transceiver designs. Lastly detailed numerical investigation is carried out to validate the theoretical results and quantify the practically realizable throughput fairness. Specifically, more than seven-fold increase in the common-backscattered-throughput among tags as achieved by the proposed designs over the relevant benchmarks corroborates their practical significance.

RFID Backscattering in Long-Range Scenarios

This paper presents a 5.8-GHz RFID tag that, by exploiting the quantum tunneling effect, significantly increases the range of backscatter radio links. We present an electronically simple Tunneling RFID Tag characterized by return gains as high as 35 dB with link sensitivity as low as −81 dBm. Without relevant increase in power consumption, the tunneling tag enables a host of new wireless sensors and Internet of Things applications that require both the long range of conventional wireless links and the low power consumption of semi-passive RFID devices. Selected measurements demonstrate a reader-to-tag separation distance 10 times higher than the maximum range of ideal semi-passive tags. Moreover, the collected experimental results allowed to outline a mathematical model demonstrating how the long-range RFID tag prototype can achieve distances unusual for this technology.

Optimal Resource Allocation Policies for Multi-User Backscatter Communication Systems.

This paper considers a backscatter communication (BackCom) system including a reader and N tags, where each tag receives excitation signals transmitted by the reader and concurrently backscatters information to the reader in time-division-multiple-access (TDMA) mode. In this system, we aim to maximize the total system goodput by jointly optimizing reader transmission power, time allocation, and reflection ratio for the cases of passive and semi-passive tags. For each case, an optimization problem is formulated, which is non-convex and can be solved by being decomposed into at most N feasible sub-problems based on the priority of allocated reader transmission power. First, for the passive tags case, by solving the convex sub-problems sequentially and comparing their maximum total goodput, we derive the optimal resource allocation policy. Then, for the semi-passive tags case, we find a close-to-optimal solution, since each sub-problem can be reformulated as a biconvex problem, which is solved by a proposed block coordinate descent (BCD)-based optimization algorithm. Finally, simulation results demonstrate the superiority of the proposed resource allocation policies.

Evaluation of RFID Tags to Permanently Mark Trees in Natural Populations.

Long-term ecological and genetic studies in natural populations of tree species require marking techniques so that individuals can be re-visited over time, even in difficult terrain. Both GPS coordinates and physical labels have disadvantages that can make re-finding trees difficult. We tested passive and semi-active radio frequency identification (RFID) tags and readers as a means to relocate individual trees. Passive RFID tags do not provide a good solution because of low transmission power of hand-held readers and strong directionality. Semi-active RFID tags provide detection over longer distances, but also suffer from strong directionality. Active RFID tags promise an improvement over semi-passive tags, and could be evaluated in a future study. We conclude that RFID technology has the potential to improve the ability of researchers to locate individual trees repeatedly under natural conditions, and can be used in conjunction with other marking techniques such as physical tags and GPS coordinates.

Is implementing RFID technology in academic libraries service beneficial? – a case study of SRM university library, Chenna

The study explores the prospects and constrains of the RFID technology implemented in SRM university central library and its performance based on the feedback received from the employees who were involved in implementation of RFID system. The data were collected from 19 employees employing questionnaire using census method and informal interview. The result shows that about 90% of the respondents felt that performance of RFID Self Service Kiosk was highly satisfied; the time taken for RFID implementation is minimum of 6 months (42.11%) and the maximum of 12 months (31.58%); RFID is preferably used for circulation (78.95%) followed by security (31.58%), user statistics (31.58%), and stack management (10.53%); and active tags (68.42%) were used the most followed by semi passive tags (21.05%), and passive tags (10.53%).

Design and Development of Sensing RFID Tags on Flexible Foil Compatible With EPC Gen 2

Taking advantage of the sensor interface capabilities of a radio frequency identification (RFID) chip, the integration of different types of sensors on printed ultrahigh frequency (UHF) RFID tags is investigated. The design, development, and testing of printed smart sensing tags compatible with the RFID standard electronic product code Gen 2 is presented. Two different strategies are employed to interface the sensors: 1) passive single-chip and 2) semipassive architectures. Both strategies provide sensor data by directly answering to the RFID reader inquiries or using a data logging mechanism to store the sensor data in the RFID chip memory. Temperature readout is measured using the embedded sensor in the RFID chip. Additionally, a light sensor and pressure sensor interfaced to a microcontroller are implemented in the passive and semipassive tags versions, respectively. For the employed RFID chip, two different UHF antennas are designed and printed using inkjet and screen printing to compare their radio frequency performances. Finally, the fabricated smart tags are fully validated through measurements in an anechoic chamber and their behaviors are compared with numerical simulation. The screen printed semipassive RFID tag with loop antenna shows a better reading range than the inkjet-printed one, whereas the passive tag can be considered as the most cost-effective system.

Study of the Readability of Passive UHF RFID Tags Placed Inside a Cargo Van by a Reader Located Outside

The aim of this paper is to study the feasibility of getting information from a cargo van returning back on its storage area by using a low cost communication system. According to the low speed of the vehicle and to the involved short distances, a UHF RFID solution is considered. An experimental study shows that passive tags may be read successfully but not in the entire space of the van. A semi-empirical numerical method based on the Geometrical Optics is derived in order to build a fast computer aided-positioning tool that may help to optimize the location of the tags. The same software tool is used for carrying out a parametric study that informs on the best antenna system to use. It is find out that a solution using passive tags and two antennas limits the theoretical results to 90% successful reading percentage whereas using semi-passive tags ensures a 100% one in the whole space of the vehicle.

A novel deployment of smart cold chain system using 2G-RFID-Sys

The cold chain system is usually adopted to follow the perishable food products during storage, transport and sale for keeping the freshness. Based on Internet of Things (IoT) technology, the sensor tags which are semi-passive tags integrated with sensors can monitor temperature in smart cold chain system. In this paper, a Refined Smart Cold Chain System (RSCCS) was proposed in which the semi-passive tags are replaced with the passive tags to reduce the cost. For availability and scalability, a new type of RFID application named 2G-RFID-Sys is applied to our design. Our proposal keeps the advantage of the original 2G-RFID-Sys and further ensures the correctness of the system execution. Not only the food producer can ensure the food freshness but also the consumer can safely purchase the products via RSCCS without accessing the backend system.

Assessing the dynamic behavior of WSN motes and RFID semi-passive tags for temperature monitoring

Wireless Sensor Networks (WSN) and Radio Frequency Identification (RFID) are two wireless technologies that are being used for cold chain monitoring and tracking. Several applications in this field have been reported in the last few years. However, there are no studies about the the dynamic behavior of this hardware and how this affects the measurements. Therefore the purpose of this study is to evaluate the dynamic behavior of the sensors. A series of trials were designed and performed, covering temperature steps between cold chamber (5°C), room temperature (23°C) and heated environment (35°C). Three WSN motes, with different sensor configurations, and four RFID tags (with and without housing), were compared. In order to assess the dynamic behavior two alternative methods have been applied for adjusting experimental data to a first order dynamic response that allows extracting the time response (τ) and corresponding determination coefficient (r2). The shortest response time (10.4s) is found for one of the RFID semi-passive tags. Its encapsulated version provides a significantly higher response (60.0s), both times are obtained with the same method. The longest τ corresponds to one of the sensors embedded in a WSN mote (308.2s). We found that the dynamic response of temperature sensors within wireless and RFID nodes is dramatically influenced by the way they are housed (to protect them from the environment); its characterization is basically to allow monitoring of high rate temperature changes and to certify the cold chain.

Times Semi-Passive RFID Tags with Double Loop Antennas Arranged as a Shifted Gate Stability Optimization

In this article, Very Crucial subject discussed in Semi-Passive RFID TAGs system stability. Semi-Passive TAGs with double loop antennas arranged as a shifted gate system stability optimization under delayed electromagnetic interferences. The double loop antenna is employed due to the fact that this antenna consists of two parallel loops; i.e., primary and secondary loops. We define Vi1(t) and Vi2(t) as the voltages in time on double loop antennas. Vi1(t) is the voltage in time on the primary loop and Vi2(t) is the voltage in time on the secondary loop. The index (i) stand for the first gate (i=1) and second gate (i=2). Due to electromagnetic interferences there are different in time delays respect to gate antenna's first and second loop voltages and voltages derivatives. The delayed voltages are Vi1(t-τ1) and Vi2(t-τ2) respectively (τ1≠ τ2) and delayed voltages derivatives are dVi1(t-Δ1)/dt, dVi2(t-Δ2)/dt respectively.

Interaction of UWB Tag Backscattering With Close Metallic Reflectors

Ultrawideband (UWB) radio frequency identification (RFID) systems for real-time objects identification and localization represent a promising solution for a future generation of RFID, as they can overcome current narrowband technology limitations. As is well known from the literature, it is very challenging to ensure a reliable RFID communication when tags are placed in proximity of metallic reflectors. For this reason, we here investigate the interaction between a UWB RFID tag and a close metallic disturber, assuming semi-passive tags operating in modulated backscattering. The impact of the metallic reflector on the tags backscattering pattern and RFID system coverage is evaluated, showing how tag detection is affected since the energy is mainly concentrated in certain directions.

Intercepting UHF RFID signals through synchronous detection

Recently, augmented ultrahigh frequency radio-frequency identification (UHF RFID) systems have been developed, and they contain additional components that can detect a tag’s backscattered response and use this information for the localization of the tag and other applications. The methods currently employed either have poor performance because the detection of the tag’s response is based on envelope detection or are costly because they are based on software-defined radio. The solution proposed in the paper is to use a method called synchronous detection to intercept tag signals. Using synchronous detection, we were able to use a conventional UHF RFID reader integrated circuit for the method, leading to a cost-effective, high-performance solution. We performed an analysis of its read rate and read range performance. The analysis showed that our receiver is capable of receiving tag signals with a read rate of 50% for passive and 66% for semi-passive tags at a 1-m distance between the tag and the receiver and is capable of receiving tag signals at a maximum distance between the tag and the receiver of 3.25 m for passive and 5.5 m for semi-passive tags, with the reader being within 8 m of the receiver. This augmented RFID system has a potential to facilitate localization and prevent the cross-read problem in RFID-based portals. In addition, it can be used as a protocol analyzer as well as a component of future Internet of Things.

A Novel UWB RFID Tag Using Active Frequency Selective Surface

This work describes an actively controlled frequency selective surface (FSS) to implement ultrawideband radio identification (RFID) tags. The tag exploits the change in the radar cross section (RCS) of the FSS, which is loaded with switching PIN diodes to modulate the backscattered time-domain response of the tag to an input ultra-wide band pulse. The basic operation theory of the system is explained. An experimental setup based on a ultrawideband radar working as a reader is proposed to measure the modulated radar cross section of the tags. As a proof of concept, a battery-assisted or semipassive tag has been developed.

Quadrature Amplitude Modulated Backscatter in Passive and Semipassive UHF RFID Systems

Passive and semipassive UHF RF identification (RFID) systems have traditionally been designed using scalar-valued differential radar cross section (DRCS) methods to model the backscattered signal from the tag. This paper argues that scalar-valued DRCS analysis is unnecessarily limiting because of the inherent coherence of the backscatter link and the complex-valued nature of load-dependent antenna-mode scattering from an RFID tag. Considering modulated backscatter in terms of complex-valued scattered fields opens the possibility of quadrature modulation of the backscatter channel. When compared with binary amplitude shift keying (ASK) or phase shift keying (PSK) based RFID systems, which transmit 1 bit of data per symbol period, and thus 1 bit per on-chip clock oscillator period, tags employing vector backscatter modulation can transmit more than 1 bit per symbol period. This increases the data rate for a given on-chip symbol clock rate leading to reduced on-chip power consumption and extended read range. Alternatively, tags employing an M-ary modulator can achieve log2 M higher data throughput at essentially the same dc power consumption as a tag employing binary ASK or PSK. In contrast to the binary ASK or PSK backscatter modulation employed by passive and semipassive UHF RFID tags, such as tags compliant with the widely used ISO18000-6c standard, this paper explores a novel CMOS-compatible method for generating M-ary quadrature amplitude modulated (QAM) backscatter modulation. A new method is presented for designing an inductorless M-ary QAM backscatter modulator using only an array of switched resistances and capacitances. Device-level simulation and measurements of a four-state phase shift keying (4-PSK)/four-state quadrature amplitude modulated (4-QAM) modulator are provided for a semipassive (battery-assisted) tag operating in the 850-950-MHz band. This first prototype modulator transmits 4-PSK/4-QAM at a symbol rate of 200 kHz and a bit rate of 400 kb/s at a static power dissipation of only 115 nW.

Revisiting RFID Link Budgets for Technology Scaling: Range Maximization of RFID Tags

Passive RF identification (RFID) tags are traditionally assumed to be downlink limited since typical tag sensitivity is considerably poorer than reader sensitivity, due to stringent power limitations. On the other hand, semipassive tags are generally uplink limited because of improvement in tag sensitivity for battery-assisted tags. In this paper, it is demonstrated that judicious choice and use of integrated circuit impedance for backscatter modulation will be needed to simultaneously maximize tag uplink and downlink ranges as passive tag designs improve. Optimal backscatter modulation indices for amplitude shift keying are derived for range maximization of next-generation low-power RFID tags.

Analysis and design of power efficient semi-passive RFID tag

The analysis and design of a semi-passive radio frequency identification (RFID) tag is presented. By studying the power transmission link of the backscatter RFID system and exploiting a power conversion efficiency model for a multi-stage AC–DC charge pump, the calculation method for semi-passive tag's read range is proposed. According to different read range limitation factors, an intuitive way to define the specifications of tag's power budget and backscatter modulation index is given. A test chip is implemented in SMIC 0.18 μm standard CMOS technology under the guidance of theoretical analysis. The main building blocks are the threshold compensated charge pump and low power wake-up circuit using the power triggering wake-up mode. The proposed semi-passive tag is fully compatible to EPC C1G2 standard. It has a compact chip size of 0.54 mm2, and is adaptable to batteries with a 1.2 to 2.4 V output voltage.

A Novel Battery-Assisted Class-1 Generation-2 RF Identification Tag Design

This paper presents a new design of an enhanced passive tag (EPT) that can extend the read range of an EPCglobal class-1 Generation-2 tag by attaching a battery-assisted circuit (BAC) to the tag integrated circuit. The BAC generates a low-power unmodulated continuous wave with frequency outside the tag operating band to supply additional power to the tag. Empirical results demonstrate that a prototype EPT has a much longer read range and is more resistant to multipath fading than a regular class-1 generation-2 tag. Unlike a semipassive tag that depends on its local battery to work, a powerless EPT can function as a regular class-1 generation-2 tag. In other words, an EPT with a charged battery is similar to a semipassive tag; after the EPT runs out of its battery power, it behaves as a regular class-1 generation-2 tag. Note that whether the EPT is powered or not, it is fully compatible with EPCglobal class-1 generation-2 specification.