Passive UHF RFID Tag Research Articles

A 2-Kb One-Time Programmable Memory for UHF Passive RFID Tag IC in a Standard 0.18 $\mu$m CMOS Process

We present a 2-Kb one-time programmable (OTP) memory for UHF RFID applications. The OTP memory cell is based on a two-transistor (2-T) gate-oxide anti-fuse (AF) for low voltage operation. Reliability of memory cell is enhanced by limiting the maximum terminal voltages of thin-oxide and thick-oxide transistors to 1.8 V and 3.3 V, respectively. Improved low power circuit design techniques are used including auto shut-off for program mode and self-timed control for read mode. To further reduce power consumption, we develop a novel power-efficient charge pump. The designed OTP is successfully embedded into a UHF passive RFID tag IC that conforms to the EPCglobal Gen-2 standard. The tag chip was fabricated in a 0.18 m 1-poly 6-metal standard CMOS process with no additional masks. The total area of the chip including the I/Os and bonding pads is 2.3 × 1.5 mm2 where the OTP memory area is only 0.43 × 0.31 mm2. Our tag IC measurement shows that the read and write currents of the OTP memory are 17 μA and 58 μA, respectively.

Position Tracking for Passive UHF RFID Tags with the Aid of a Scanned Array

Thanks to the proliferation of radio frequency identification systems (RFID), applications have emerged concerning positioning techniques for inexpensive passive RFID tags. The most accurate approaches for tracking the tag’s position, deliver precision in the order of 20 cm over a range of a few meters and require moving parts in a predefined pattern (mechanical antenna steering), which limits their application. Herein, we introduce an RFID tag positioning system that utilizes an active electronically-steered array, based on the principles of modern radar systems. We thoroughly examine and present the main attributes of the system with the aid of an finite element method simulation model and investigate the system performance with far-field tests. The demonstrated positioning precision of 1.5°, which translates to under 1 cm laterally for a range of a few meters can be helpful in applications like mobile robot localization and the automated handling of packaged goods.

Testing the effects of temperature and humidity on printed passive UHF RFID tags on paper substrate

This article is an interesting substrate material for environmental-friendly printable electronics. In this study, screen-printed RFID tags on paper substrate are examined. Their reliability was tested with low temperature, high temperature, slow temperature cycling, high temperature and high humidity and water dipping test. Environmental stresses affect the tag antenna impedance, losses and radiation characteristics due to their impact on the ink film and paper substrate. Low temperature, temperature cycling and high humidity did not have a radical effect on the measured parameters: threshold power, backscattered signal power or read range of the tags. However, the frequency response and the losses of the tags were slightly affected. Exposure to high temperature was found to even improve the tag performance due to the positive effect of high temperature on the ink film. The combined high humidity and high temperature had the most severe effect on the tag performance. The threshold power increased, backscattered power decreased and the read range was shortened. On the whole, the results showed that field use of these tags in high, low and changing temperature conditions and high humidity conditions is possible. Use of these tags in combined high-humidity and high-temperature conditions should be carefully considered.

Constrained-Design of Passive UHF RFID Sensor Antennas

Passive UHF RFID tags may be used, beside labeling, to remotely observe the physical/chemical change of the tagged object, through modulation of their impedance and gain, thus acting as sensor antennas. The design of this new class of devices can be mastered by fully understanding the relationship between communication and sensing with the purpose to balance the maximization of the dynamic range of the response with the stability of the read distance. A new kind of communication/sensing nomogram permits to display both behaviors in a unitary way and to predict their physical limits, as well as to formalize a multi-parameter general-purpose optimization methodology. The procedure is demonstrated by application to the design of a strain-gauge tag and of a level-detector wireless sensor.

A novel ultra low power ASK demodulator for a passive UHF RFID tag compatible with C1 G2 EPC standard protocol

In order to reduce the power consumption of RFID tags and increase the reading range of RFID systems, this paper proposes an ASK demodulator that uses a new approach to reduce the threshold voltage of diode connected MOS transistors as an obstacle in the design of the envelope detector. Also, an ultra low power comparator is used for further power reduction. This circuit has been simulated in a 0.18 μm CMOS technology to satisfy EPC Class 1 Generation 2 standard protocol emphasizing on the reduction of power consumption. The proposed circuit can correctly demodulate the minimum input RF signal amplitude of 180 mV for modulation depths of 55---100 % with 40---160 kb/s data rates. A total power consumption of less than 290 nW is achieved at a 1.2 V power supply. Effects of the input signal additive white noise as well as the process and temperature variations on the signal demodulation is also investigated in this paper.

Towards inkjet-printed low cost passive UHF RFID skin mounted tattoo paper tags based on silver nanoparticle inks

The present work describes the inkjet printing and low temperature sintering of silver nanoparticle inks onto transfer tattoo paper. Our approach results in silver features of excellent resolution and conductivity and, subsequently the first passive UHF RFID transfer tattoo tags functional mounted on human skin of improved performance when compared to screen printed passive UHF RFID transfer tattoo paper tags. Moreover, inkjet printed passive UHF RFID transfer tattoo tags show similar performance to copper etched passive UHF RFID tags on plastic substrates. This study compares the image quality (resolution) and electrical performance of two commercial silver nanoparticle inks inkjet printed on transfer tattoo paper. The optimal printing and sintering parameters to obtain high resolution features of resistivities 20 to 57 times the resistivity of bulk silver (1.59 × 10−6 ohm cm) are described. We demonstrate how, by selectively depositing ink in specific areas of the antenna, read distance of passive UHF RFID tags can be increased from 54 to 68 cm whilst decreasing the amount of ink used by 33%. Furthermore, this approach results in inkjet printed passive UHF RFID tattoo tags with larger read distance than silver screen printed passive UHF RFID tattoo tags, 45 cm, and similar to copper etched passive UHF RFID plastic tags, 75 cm. Moreover, inkjet printed passive UHF RFID tattoo tags in this work are considerably thinner (1–5 μm) than screen and etched passive UHF RFID tags (tens of micrometers) hence, making the former more appealing to the end user. In addition to this, inkjet printing is compatible with large area manufacturing techniques and has the potential to evolve as one of the most promising RFID mass-production techniques. Therefore, this work represents a step towards the commercialization of on-body transfer tattoo paper passive UHF RFID tags.

Measurement of Effective Reading Distance of UHF RFID Passive Tags

Currently, for manufacturing UHF RFID passive tags, the online inspection mechanism is very simple. This mechanism tries to read tag IDs in the near field, and hence validates tag’s usability. For UHF RFID applications, tag usability is a very rough indicator and cannot characterize the performance of a tag accurately. In practice, effective reading distance is the key performance index of a tag. This study proposes chip’s turn-on power approach to characterize the effective reading distance of UHF RFID passive tags. The experimental results presented in this paper demonstrated the feasibility of this approach. Moreover, in comparison with the large-scale setup, this mini-scale setup produces a smaller error in the estimation of the effective reading distance. Using a mini anechoic chamber, the mini-scale setup can be adopted in practice for online tag performance inspection to grade tag’s compliance with effective reading distance.

A Study of Management System for Medical Equipment using UHF Passive RFID Tags

A Study of Management System for Medical Equipment using UHF Passive RFID Tags

Broadband UHF RFID Passive Tag Antenna for Near-Body Applications

One challenge for UHF RFID passive tag design is to obtain a low-profile antenna that minimizes the influence of near-body or attached objects without sacrificing both read range and universal UHF RFID band interoperability. A new improved design of a RFID passive tag antenna is presented that performs well near problematic surfaces (human body, liquids, metals) across most of the universal UHF RFID (840-960 MHz) band. The antenna is based on a low-profile printed configuration with slots, and it is evaluated through extensive simulations and experimental tests.

Enhanced UHF RFID Sensor-Tag

A cost-effective integration of passive UHF RFID tags and sensors is still a challenge. In such a field, authors have already proposed a label-type multi-antenna Sensor-Tag, an RFID device accepting as input a generic sensor and allowing the transmission of the measured data towards a standard RFID reader. In this work a new enhanced version of Sensor-Tag is presented. It is based on optimized tag antennas designed by taking into account both size constraints and coupling effects. Compared with the old version, an appreciable size reduction is obtained and the working distance doubled, being now as good as a long range passive UHF tag.

On the use of passive UHF RFID tags in the pharmaceutical supply chain: a novel enhanced tag versus high-performance commercial tags

Item-level RFID-based tracing systems are of growing interest both from industrial and scientific standpoints. In such a context, the choice of the most adequate RFID tag, in terms of shape, frequency, size and reading range, is crucial. The potential presence of items containing materials hostile to the electromagnetic propagation exacerbates the problem. In addition, the peculiarities of the different RFID-based checkpoints make the requirements for the tag even more stringent. In this work, the performance of several commercial UHF RFID tags in each step of the pharmaceutical supply chain has been evaluated, confirming the foreseen criticality. On such basis, a guideline for the electromagnetic design of new high-performance tags capable of overcoming such criticalities has been defined. Finally, driven by such guidelines, a new enhanced tag has been designed, realised and tested, demonstrating that high performance item-level tracing systems can actually be implemented also in critical operating conditions.

Design and implementation of an ultra-low power passive UHF RFID tag

This paper presents a fully integrated passive UHF RFID tag chip complying with the ISO18000-6B protocol. The tag chip includes an RF/analog front-end, a baseband processor, and a 512-bit EEPROM memory. To improve power conversion efficiency, a Schottky barrier diode based rectifier is adopted. A novel voltage reference using the peaking current source is discussed in detail, which can meet the low-power, low-voltage requirement while retaining circuit simplicity. Most of the analog blocks are designed to work under sub-1 V to reduce power consumption, and several practical methods are used to further reduce the power consumption of the baseband processor. The whole tag chip is implemented in a TSMC 0.18 μm CMOS process with a die size of 800 × 800 μm2. Measurement results show that the total power consumption of the tag chip is only 7.4 μW with a sensitivity of −12 dBm.

Embedded multislotted PIFAs for remotely powered passive UHF RFID tags

We present a compact planar antenna that can be embedded within low-frequency UHF power-harvesting tag platforms.The antenna is a planar inverted-F antenna-type design with a set of optimized slots and provides large bandwidths, comparable to half-wave dipoles, while maintaining a low profile and small area. Hence, it can be embedded within the PCB of power-harvesting tags operating even at low UHF frequencies, resulting in a compact, slim overall device. We demonstrate this by embedding the antenna within a 430 MHz low-power discrete-component harvester tag, and we have designed and manufactured and verified antenna performance by both antenna measurements and tag link measurements. An added advantage of this topology is that tags with this antenna can be placed very near large metal structures without shorting or detuning, unlike tags with standard external dipole antennas. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2379–2383, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27096

Design of Implanted RFID Tags for Passive Sensing of Human Body: The STENTag

Numerical processing of passive UHF-RFID tags' response may provide physical insight about the hosting object or about the nearby environment. This idea is here extended to implanted antennas with the purpose to sense the evolution of some human physiological and pathological process involving a local change of effective permittivity inside the body. The goal is to understand how master the design of this class of devices taking into account both communication and sensing capabilities. An ad hoc design methodology is here presented and discussed by means of a realistic medical case concerning the modification of an endo-vascular device to achieve a STENTag able to sense the state of the vessel wherein it has been implanted.

Design of the UHF RFID Passive Tag Vibration Measurement Instrument

According to the anti-vibration performance test requirements to the UHF RFID passive tag in the application of civil aviation luggage transport, the paper designs a vibration measurement instrument for UHF RFID passive tag. A vibration test scheme is designed based on non-resonance single-axis inertial vibration principle, which builds the mathematical model and vibration equation. Thereafter, a software ADAMS is applied to simulate the vibration performance, and the effects of motor speed, eccentric quality and spring stiffness coefficient are analyzed to provide the basis for the further manufacturing. Finally, a prototype is realized, and a vibration performance test based on piezoelectric accelerometer is proposed to obtain the performance parameters. The test shows that the parameters including vibration frequency and the maximum peak to peak vibration displacement satisfy the design requirements.

A Selective Ink Deposition Method for the Cost-Performance Optimization of Inkjet-Printed UHF RFID Tag Antennas

A selective ink deposition method is proposed for fabricating inkjet-printed passive UHF RFID tag antennas with optimized cost-performance ratios. The deposition method is based on identifying areas with high surface current densities on a given tag antenna and applying additional silver nanoparticle ink onto such areas to increase tag read range. In this paper, the proposed method is experimentally verified by utilizing the method on a small dipole tag antenna. Several ink deposition schemes are created, and their read range performances and ink consumptions are presented.

Performance of High-Permittivity Ceramic-Polymer Composite as a Substrate for UHF RFID Tag Antennas

A high-permittivity ceramic-polymer composite substrate is fabricated and proposed for its potential use in UHF RFID tags. The substrate is developed using high-permittivity Barium Titanate (BaTiO3) ceramic powder mixed with polydimethylsiloxane (PDMS) polymer. The resulting composite achieves a soft, hydrophobic, heat resistant, low loss, and flexible material with high dielectric constant. The percentage of the ceramic powder in the composite helps in achieving variable permittivity values. When this material is used as a substrate for a tag antenna, it will help the tag to be reduced in size, to conform to uneven or rough surface, and to be less vulnerable to breakage or other environmental damages. A small passive UHF RFID tag antenna is designed, fabricated, and attached to this type of composite substrate, to demonstrate the performance of this composite material.

Vector Backscattered Signals Improve Piggyback Modulation for Sensing With Passive UHF RFID Tags

We expand our “piggyback modulation” technique to integrate sensing functions with existing standard passive UHF RFID tags through wireless coupling. Instead of focusing on the scalar backscattered power that is proportional to the radar cross section (RCS), we exploit the vector backscattered signal with piggyback modulation. Measuring both amplitude and phase of the backscattered wave makes advanced demodulation possible. The measurement setup, experimental results, demodulation analysis, and numerical simulation for the conventional amplitude-shift keying (ASK) and quasi-4-quadrature amplitude modulation (quasi-4-QAM) are presented. Quasi-4-QAM demodulation reduces the interference between two independent data streams and improves the bit error rate for the same RF power. While we do not show explicit data from any given sensor, we do show that a generic sensor signal will be improved with our technique.

Design of 512-bit logic process-based single poly EEPROM IP

A single poly EEPROM cell circuit sharing the deep N-well of a cell array was designed using the logic process. The proposed cell is written by the FN tunneling scheme and the cell size is 41.26 μm2, about 37% smaller than the conventional cell. Also, a small-area and low-power 512-bit EEPROM IP was designed using the proposed cells which was used for a 900 MHz passive UHF RFID tag chip. To secure the operation of the cell proposed with 3.3 V devices and the reliability of the used devices, an EEPROM core circuit and a DC-DC converter were proposed. Simulation results for the designed EEPROM IP based on the 0.18 μm logic process show that the power consumptions in read mode, program mode and erase mode are 11.82, 25.15, and 24.08 μW, respectively, and the EEPROM size is 0.12 mm2.

A passive UHF RFID tag chip with a dual-resolution temperature sensor in a 0.18 μm standard CMOS process

This paper presents a passive EPC Gen-2 UHF RFID tag chip with a dual-resolution temperature sensor. The chip tag integrates a temperature sensor, an RF/analog front-end circuit, an NVM memory and a digital baseband in a standard CMOS process. The sensor with a low power sigma—delta (ΣΔ) ADC is designed to operate in low and high resolution modes. It can not only achieve the target accuracy but also reduce the power consumption and the sensing time. A CMOS-only RF rectifier and a single-poly non-volatile memory (NVM) are designed to realize a low cost tag chip. The 192-bit-NVM tag chip with an area of 1 mm2 is implemented in a 0.18-μm standard CMOS process. The sensitivity of the tag is −10.7 dBm/−8.4 dBm when the sensor is disabled/enabled. It achieves a maximum reading/sensing distance of 4 m/3.1 m at 2 W EIRP. The inaccuracy of the sensor is −0.6 °C/0.5 °C (−1.0 °C/1.2 °C) in the operating range from 5 to 15 °C in high resolution mode (−30 to 50 °C in low resolution mode). The resolution of the sensor achieves 0.02 °C (0.18 °C) in high (low) resolution mode.