Ultra High Frequency Radio Frequency Identification Research Articles

LS Channel Estimation and Signal Separation for UHF RFID Tag Collision Recovery on the Physical Layer.

In a passive ultra-high frequency (UHF) radio-frequency identification (RFID) system, tag collision is generally resolved on a medium access control (MAC) layer. However, some of collided tag signals could be recovered on a physical (PHY) layer and, thus, enhance the identification efficiency of the RFID system. For the recovery on the PHY layer, channel estimation is a critical issue. Good channel estimation will help to recover the collided signals. Existing channel estimates work well for two collided tags. When the number of collided tags is beyond two, however, the existing estimates have more estimation errors. In this paper, we propose a novel channel estimate for the UHF RFID system. It adopts an orthogonal matrix based on the information of preambles which is known for a reader and applies a minimum-mean-square-error (MMSE) criterion to estimate channels. From the estimated channel, we could accurately separate the collided signals and recover them. By means of numerical results, we show that the proposed estimate has lower estimation errors and higher separation efficiency than the existing estimates.

Passive UWB RFID for Tag Localization: Architectures and Design

In the new scenarios foreseen by the Internet of Things, industrial and commercial systems will be required to detect and localize tagged items with high accuracy, as well as to monitor the level of certain parameters of interest through the deployment of wireless sensors. To meet these challenging requirements, the adoption of passive and semi-passive ultra-wideband (UWB) radio-frequency identification (RFID) appears a promising solution, which overcomes the limitations of standard Gen.2 ultra-high frequency (UHF) RFID. The design and implementation of such systems pose several practical constraints, impacting the overall network architecture. In this paper, the main issues and challenging aspects for the design of a UWB-RFID network considering architectural and protocol choices are discussed in a unitary framework, and practical solutions, accounting for the presented issues, are proposed. Moreover, the possible integration of UWB-RFID with standard Gen.2 UHF-RFID is proposed as an interesting option, discussing architectural solutions, their advantages, and drawbacks.

Broadband circularly polarized antenna with moon-shaped parasitic element

A broadband circularly polarized (CP) circular patch antenna with an L-shaped ground plane and parasitic element is studied. The use of this L-shaped ground is to achieve short probe feed connection to the circular patch, while maintaining a certain height between the circular patch and ground plane, so that good impedance matching and bandwidth enhancement can be attained. To achieve CP radiation, two notches are initially loaded diagonally into the circular patch, and to further enhance the CP bandwidth, a novel technique of loading a small size moon-shaped parasitic element into the notched circular patch is proposed. By doing so, the CP bandwidth of proposed antenna can be tremendously increased by approximately 10%. The experimental results show that the proposed CP antenna can yield impedance bandwidth and CP bandwidth of 835–1150 MHz and 839–968 MHz, respectively, with good gain level of 7.6 dBic. Therefore, this proposed wideband CP antenna can be used for UHF (ultrahigh frequency) RFID (radio frequency identification) reader antenna that operates within the universal RFID bands (840 − 960 MHz). © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:387–395, 2016

The multiple loop antenna for enhanced readability performances of near-field UHFRFID applications

This research is concerned with a multiple loop antenna applicable to near field ultra-high frequency (UHF) radio frequency identification (RFID). The proposed multi-loop antenna is configured to induce the robust and even magnetic field distributions in the Hx, Hy, and Hz orientations so as to achieve the enhanced readability performances in all directions (i.e., x, y, and z). Simulations were carried out using CST Microwave Studio to determine the impedance bandwidth (|S11|<−10 dB) in the frequency range of 920–925 MHz (i.e., Thailand's UHF RFID standard) and to investigate the Hx-, Hy-, and Hz-oriented magnetic field distributions. A prototype antenna of 14 cm × 16 cm × 0.6 mm (W × L × H) in overall dimension was subsequently fabricated on an FR4 substrate connected to a coaxial cable. In this research, the Hx-, Hy-, and Hz-oriented magnetic field distributions of the prototype antenna were measured in the x-axis, y-axis, and x–y plane and are in good agreement with the simulation results. The measured readability performances in the x-, y-, and z-directions in which seven near field UHF RFID tags were deployed unobstructed (i.e., in open air) are respectively 25.27%, 31.73%, and 85.43%. Furthermore, the performances on the antenna readability with the tags attached to the microcentrifuge tubes are 30.55%, 25.90%, and 69.09% for the x-, y-, and z-directions. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:402–417, 2016.

Innovating RFID for Future Applications: A Capacitive Coupled Antenna Design for UHF RFID Application

In the 2015 International Microwave Symposium (IMS 2015) Student Design Competition (SDC) held in Phoenix, Arizona, a new challenge was introduced by the Microwave Theory and Techniques Committee for RFID Technologies (MTT-24), dealing with the topic of ultrahigh-frequency (UHF) RF identification (RFID) tag sensitivity.

Analysis and Design of a Long Range PTFE Substrate UHF RFID Tag for Cargo Container Identification

Abstract In this paper, a high-performances microstrip antenna for UHF (ultra high frequency) RFID (radio frequency identification) tag is designed, prototyped and tested. The antenna consists of two main components: a 1.52 mm RT/duroid 5880 laminate substrate on which the antenna is designed and a 10 mm polytetrafluoroethylene (PTFE) dielectric material placed as a separator between the antenna and the reference ground plane for the microstrip antenna. With this structure, the RFID tag can reach a maximum reading distance of 19 m, although the antenna has a compact size of 80 mm × 50 mm. The long reading distance is obtained by attaching to the antenna an RFID chip that can provide a reading sensitivity of −20.5 dBm. The high bandwidth from 677 MHz to 947 MHz measured at −10 dB, makes the tag being usable worldwide especially for cargo container identification, the main purpose of this research.

Embedded UHF RFID Tag for Durability Monitoring in Concrete

This paper describes the design of a battery-assisted Ultra-High Frequency (UHF) Radio-Fre- quency IDentification (RFID) tag suitable for embedding in concrete materials and its measurement in a mortar slab. The device is built to communicate wirelessly not only the ID number of the RFID chip but also the digitalized output of a strain gauge sensor. Design optimizations of the RFID antenna is based on published permittivity and conductivity values of concrete. Experimental read ranges are measured from 800 to 1000 MHz with the help of commercial test equipment. Reading is possible up to 50 cm from the surface of a mortar block for a tag embedded 5 cm below the surface. This result is the first published one for RFID tags embedded in concrete or mortar.

Brush-Painting and Photonic Sintering of Copper Oxide and Silver Inks on Wood and Cardboard Substrates to Form Antennas for UHF RFID Tags

Additive deposition of inks with metallic inclusions provides compelling means to embed electronics into versatile structures. The need to integrate electronics into environmentally friendly components and structures increases dramatically together with the increasing popularity of the Internet of Things. We demonstrate a novel brush-painting method for depositing copper oxide and silver inks directly on wood and cardboard substrates and discuss the optimization of the photonic sintering process parameters for both materials. The optimized parameters were utilized to manufacture passive ultra high frequency (UHF) radio frequency identification (RFID) tag antennas. The results from wireless testing show that the RFID tags based on the copper oxide and silver ink antennas on wood substrate are readable from ranges of 8.5 and 11 meters, respectively, and on cardboard substrate from read ranges of 8.5 and 12 meters, respectively. These results are well sufficient for many future wireless applications requiring remote identification with RFID.

Shifted Source Impedance and Nonlinearity Impact on RFID Transponder Communication for Drive-Level Offsets

A measurement and analysis method to quantify the communication quality for ultrahigh-frequency radio frequency identification (RFID) transponder chips under a shifting source environment is presented. A detailed description of theory, setup, and procedure is provided. The differences in on/off impedance ( $\vert\Delta\Gamma\vert$ -value) of the transponder chip are critical for backscatter modulation and, therefore, the overall communication and transponder response. In the present work, a new quantity which includes the difference in on/off impedance, as well as arbitrary source impedance, is defined as an overall figure of merit. A qualitative analysis, considered as novel in the RFID community, shows the impact a source impedance shift has on the communication quality. The bare chip measurement setup enables an ASK modulated wake up signal, realized as a pulse train. The chip response consisting of modulated impedance states are measured in a pulse profile setup. Results show that different degrees of nonlinearity in a transponder chip, depending on vendor and type, will have impact on the communication performance.

Achieving uniform perpendicular magnetic field distribution for near‐field ultra‐high frequency radio‐frequency identification

In this study, a new antenna is proposed to achieve uniform perpendicular magnetic field distribution for near-field ultra-high frequency radio-frequency identification. The antenna is based on ‘interdigital-oppositely directed currents (ODCs)’ that is formed by introducing another current between the two oppositely directed currents of ODCs. By adjusting the feeding phase of the newly introduced current, the uniformity of perpendicular magnetic field distribution can be improved. The design procedure of the antenna is presented and the uniform perpendicular magnetic field distribution of the antenna is achieved and verified by experiments. When the transmitting power of the proposed antenna is 1 W, the interrogation area for 100% tag detection is 49 × 16 cm2 with an observing height of 5 cm for Impinj J41 near-field tags.

Radar cross‐section measurement in millimetre‐wave for passive millimetre‐wave identification tags

The passive millimetre-wave identification (MMID) technology was introduced few years ago, exploiting the advantages of the passive ultra-high frequency (UHF) radio frequency identification (RFID). The communication is based on backscattering modulation, related to the radar cross-section (RCS) of the transponder. Thus, the need of accurate RCS measurement in the V-band arises. This work presents two methods to measure the RCS of any antenna in the particular case of MMID from 57 to 66 GHz. The studied methods require some precautions in millimetre-wave compared with measurements done in the UHF band. The two approaches highlight the methodology for accurate RCS measurement while the methods are evaluated through an example. A horn antenna is used as a MMID tag antenna and the RCS of the antenna is studied across three different loads as in UHF RFID: the short circuit, the open circuit and the matched load. The proposed methods provide a good accuracy and are validated by comparing the measurement results to the simulation.

Threshold voltage-level change in ASK demodulator related to RF input signal amplitude for the ultra-high frequency RFID passive tag

In this paper, an amplitude shift keying (ASK) demodulator with 100% modulation depth is proposed. In order to achieve the higher power and wider reading range the designed ASK demodulator works in the ultra-high frequency. In this design, the average detector and voltage divider are used in order to define the appropriate threshold voltage level for the radio frequency input signal which leads to the accurate data detecting even at long distances between the tag and reader. In addition, for diminishing the power dissipation of the proposed demodulator, an enable input is used in the buffer and comparator. This circuit is simulated in 0.18 μm complementary metal–oxide–semiconductor (CMOS) technology with Cadence software. Its power dissipation and chip area are 3.9 nW and 0.0025 mm2, respectively.

UHF RFID Localization Based on Evaluation of Backscattered Tag Signals

This paper introduces a 2-D position measurement system for passive ultra-high frequency (UHF) radio frequency identification (RFID) tags based on evaluation of backscattered transponder signals. The main application of the system is the localization of stationary objects tagged with RFID transponders. By combining phase and amplitude evaluation, the accuracy and the robustness of the position estimates are significantly improved compared with either approach alone. A multiple input multiple output system in which, sequentially, each frontend is configured to work as a transmitter while the remaining frontends serve as receivers is used to enable position estimation. For proof of concept, a local position measurement system demonstrator was built comprising conventional passive EPCglobal Class-1 Gen-2 UHF RFID tags, a commercial off-the-shelf RFID reader, eight transceiver frontends, baseband hardware, and signal processing. Measurements were carried out in an indoor office environment where the $3.5~{\mathrm{ m}} \times 2.5$ m measurement zone was surrounded by drywalls and concrete floor and ceiling. The experimental results showed accurate localization with a root-mean-square error of 0.020 m and a median error of 0.011 m. To determine the limits of the system, accuracy simulations were performed, which confirm the experimental results.

Development of novel wireless sensor for food quality detection

In this paper we present a wireless sensor for the monitoring of food quality. We integrate sensing capability into ultrahigh frequency (UHF) radio-frequency identification (RFID) tags through the relationship between the physical read-range and permittivity of the object we label with the RFID tags. Using the known variations of food permittivity as a function of time, we can detect the contamination time at which a food product becomes unacceptable for consumption based on the measurement of read-range with the as-designed sensing tags. This low-cost UHF RFID passive sensor was designed and experimentally tested on beef, pork, and cheese with the same storage conditions as in supermarkets. The agreement between the experimental and simulation results show the potential of this technique for practical application in food-quality tracking.

Measurement results for multichannel transmit beamforming tag direction detection in passive ultra‐high frequency radio‐frequency identification systems

As an alternative to classical ultra-high frequency (UHF) radio-frequency identification (RFID) tag localisation methods (e.g. angle of arrival or received signal strength), a new angle-of-activation approach is presented that uses digital multichannel transmit beamforming. By pivoting the main lobe of the interrogator's transmit antenna array utilising the very sensitive response threshold of passive UHF RFID tags, the tag direction is estimated. The presented three-channel digital beamforming hardware pivots the main lobe of a circularly polarised antenna array in a range of ±52° with an angular resolution of 0.02°. It estimates the direction of a circularly polarised tag with a mean measured accuracy of 0.9° in a basic multipath environment.

Design and development of wideband patch antenna for UHF RFID metal mountable tag

ABSTRACTIn this research, two low profile metal mountable patch antenna designs for passive ultra-high frequency (UHF) radio frequency identification (RFID) tag are proposed. The complex impedance matching between the antenna and the referenced microchip, Alien-Higgs 3 whose impedance , is realized through an inductively coupled loop feed structure where it provides the needed reactance for the tag antenna. To enhance the bandwidth of the antenna, multiple co-planar radiating patches are employed to excite several resonant modes for worldwide use. The wide impedance bandwidth also compensates for fabrication inaccuracy which could shift the operating frequency of the final antenna design. The final dimensions of the antennas are 87 × 45 × 1.6 mm3 and 130 × 63 × 1.6 mm3. The measured impedance bandwidths of the proposed antennas when mounted on a metal plate are 155 MHz (RL ≥ 3 dB), which is from 830 to 985 MHz, and 117 MHz (RL ≥ 6 dB), which is from 850 to 967 MHz, respectively. The maximum simulated gains are −7 and −11 dB at the operating frequency of 915 MHz. Based on the measurement results, it is expected that the proposed antenna would be able to provide a reasonable read range of at least 2 m throughout the entire UHF RFID band when being attached on metal objects.

Employing Ultrahigh-Frequency RFID Technology on Deer Farm Managment

This project uses ultrahigh-frequency (UHF) ear tags and readers with a readable range of 3 to 5 m. Forty stags were tagged with radio-frequency identification (RFID) ear tags and allocated into 20 pens. When deer with RFID ear tags walked through the aisle, handheld RFID readers, used as personal digital assistants (PDAs), and stationary RFID readers in frequency range received signals from the tags, and individual deer tag data were transmitted immediately and completely through wireless PDAs to a computer. The inputted data were sent to the deer-farm management system to be collated and organized. Farmers obtained individual deer data without approaching the deer, which decreased the risk of the deer attacking. Employing UHF-RFID technology integrated with software contributes to enhancing the efficiency of deer identification and farm management.

Wideband Compact CPW-Fed Circularly Polarized Antenna for Universal UHF RFID Reader

A compact circularly polarized slot antenna is proposed in this communication, which has a much wider operation bandwidth compared to the antennas with similar sizes. This antenna is designed for universal ultrahigh frequency (UHF) radio-frequency identification (RFID) reader applications. The antenna is coplanar waveguide (CPW) fed by an L-shaped feeding line. To achieve good impedance matching and broadband CP operation, two L-shaped strip lines are inserted into the circular slot in the ground plane. The measured 10-dB return loss bandwidth is 380 MHz (618-998 MHz, 47.0% centered at 808 MHz). The measured 3-dB axial ratio bandwidth is about 332 MHz (791-1123 MHz, 34.7% centered at 957 MHz). The overall size of the antenna is 120 × 120 × 0.8 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .

Quantitative evaluation of power transfer efficiency of UHF RFID passive systems

A procedure to evaluate the power transfer efficiency of ultra-high-frequency (UHF) radio-frequency identification (RFID) passive systems is presented. The ratio between the available power at the tag antenna and the input power into the reader antenna is measured for the first time in the UHF RFID frequency band. The power absorbed by the tag antenna is measured using a transition and matching circuit.

Quadruple‐feed beam‐controlled antenna array for the localisations of ultra‐high‐frequency radio‐frequency identification tags

Item-level tagging has been required to the retail market with densely placed items as well as the production line. Owing to the multi-path fading, the blind spots where the tag is non-responsive can be created. Furthermore, in case of the indoor radio-frequency identification (RFID) localisation system, additional circuits and localisation algorithms are indispensable for accurate localisation of RFID tags. In this study, in order to solve this problem, the beam-controlled antenna array with a quadruple beamforming network which generates multiple beams is presented for ultra-high-frequency (UHF) RFID systems. The proposed quadruple-feed antenna array can cover the wide spatial coverage, and the main beam directions of the proposed array can be controlled by selecting the appropriate input port of the quadruple network. The fabricated antenna array with the quadruple-feed network operates at the 902-928 MHz band and produces scannable multiple beams for UHF RFID localisation system within the wide interrogation zone.