UHF Radio Frequency Identification Reader Research Articles

Circularly Polarized Cross-Dipole Antenna for UHF RFID Readers Applicated in the Warehouse Environment

In this paper, we proposed a broadband circularly polarized antenna with wide beamwidth. The main structure of the proposed antenna is a combined cross-polarized dipole antenna with four metal arms feeding by a single coaxial cable and two 90° phase delay lines. In order to attain a wide beamwidth antenna performance that can be used in a warehouse environment, we innovatively bent the metal arms and added a metal plane at a specific location to gain maximum beamwidth and the highest achievable gain. Especially, the application of folded metal arms not only reduce the space size of antenna, but also possess good axial ratio characteristic. The measurement illustrates that the antenna prototype achieves S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> < -10 dB impedance bandwidth (IBW) of 40% (820 - 1230 MHz), a 3-dB axial ratio bandwidth (ARBW) of 7.3% (895 - 970 MHz), and a maximum half-power beamwidth (HPBW) of 104° (@915 MHz). In addition, the good radiation characteristics of a gain of 6.33 dBic and an average radiation efficiency of 76.3% were measured in the operating bandwidth, in which make the antenna a good candidate for the hasty logistics radio frequency identification (RFID) system.

RFID Based Marathon Tracking System

Abstract: The most daunting task in any type of marathon running event is the correct, impartial tracking and positioning of participating athletes. Notwithstanding the tens of thousands of marathon runners congregating at the starting point of the race, this system accurately tracks the chip-time of each and every runner thus providing the organizers with fair and exact results at the end of the event. All this technological leap in race timing is only possible via Radio-frequency identification (RFID). This cost-effective marathon tracking system implements disposable passive RFID tags on the bibs of the marathon runners to track their chip-time as soon as they pass the starting point of the race where the UHF RFID reader is positioned. Keywords: RFID, Marathon, Arduino Uno, UHF, Passive RFID tag, chip-time.

Remote Control System for Battery-Assisted Devices with 16 nW Standby Consumption.

One of the biggest impacts of the vision ‘Internet of Things’ is the massive number of connected devices, where billions of nodes will exchange data, information and commands. While wireless systems offer advantages such as increased flexibility, they also introduce one major challenge: how to power each individual node. In many cases, there is no way around the use of batteries. To minimize the environmental impact, increasing the battery’s longevity is the most important factor. This paper introduces a wireless battery-assisted node that has a drastically reduced energy consumption in the standby mode. The state (on/off) will be changed by harvesting a radiofrequency signal. A latching switch connects or disconnects the load—for example, a microcontroller—and the battery. The switch is connected to a charge pump which converts an AC (alternating current) signal into a usable DC (direct current) control signal. An antenna is mounted to the charge pump via a matching network. An electromagnetic wave is emitted by a remote control switch that switches the system on and off. The used frequency is MHz and therefore in the UHF RFID (ultra high frequency radio frequency identification) band. The measurement results show that the wireless node consumes less than in the standby mode. The remote controlling is possible from a distance of more than . The presented system can be integrated in further work on a UHF RFID tag. Thus, the existing protocol standard can be used to identify the object to be switched. By custom commands, the switching request can be transmitted from the remote control (UHF RFID reader) to the switching node.

Design of Circularly Polarized Modified Minkowski Fractal Based Antenna for UHF RFID Reader Applications

A compact, square shaped microstrip fractal antenna with asymmetrical pairs of T-slits for circularly polarized (CP) radiation and radio frequency identification (RFID) reader applications is proposed and experimentally investigated. Design is based on narrow slit modified Minkowski island fractal geometry. Circular polarization along with size reduction is achieved by inserting four symmetrical pairs of T-slits at the square patch boundary of the single-probe-feed radiator. Proposed geometry is tuned at resonant frequency of 914 MHz by optimization of dimensions of the two T-slits. Compactness of the antenna is achieved by increasing the overall sizes of the slits. Antenna is fabricated on FR4 substrate with a size of 47.2×47.2×1.6 mm3 (0.143λ0 X 0.143λ0 X 0.005λ0) and tested to validate the simulated results. The 3-dB axial-ratio (AR) bandwidth and impedance bandwidth of the proposed antenna design are found to be 7 MHz (911-918 MHz) and 24 MHz (909-933 MHz) respectively. A design equation is develped based on the parametric study that can be used to design a compact antenna with CP for UHF RFID applications covering the frequency range from 887 to 1023 MHz.

Compact 3-D-Printed Circularly Polarized Antenna for Handheld UHF RFID Readers

In this letter, the aptness of the combination of three-dimensional (3-D) printing and radio frequency identification (RFID) is faced by presenting a compact, low-profile, and cost-effective circularly polarized antenna for handheld UHF RFID reader. The radiating element has been realized through a circular array of four inverted-F monopoles, where the array elements are excited with a 90° phase offset through a microstrip feeding network, realized in 3-D printing technology as well. Taking advantage from low losses and moldability of the 3-D printing materials joint to a specific design strategy, the proposed antenna realizes an improved gain and an appreciable size reduction if compared with the state of the art.

Eccentric annular slot patch antenna with frequency agility for UHF RFID reader applications

The design of a simple ultrahigh frequency RFID (radio frequency identification) reader antenna that can operate within the North America RFID band (902–928 MHz) is studied. To generate circular polarization (CP) radiation in this band, a novel method of loading two narrow open-ended slots (slits) into an eccentric annular slot patch is proposed. To allow optimum impedance matching with enhanced CP bandwidth, the radiating patch is loaded to an L-shaped ground plane. From the experimental results, the proposed antenna can yield an impedance bandwidth (10-dB return loss) between 650 MHz to 1125 MHz, while good CP bandwidth (3-dB axial ratio, AR) from 901 MHz to 930 MHz is also attained. Furthermore, gain level and efficiency of more than 7.8 dBic and 90%, respectively, were also measured. By simply removing one of the slits, this proposed antenna can also be modified to operate within the China (840–846 MHz) and European (865–868 MHz) RFID band.

Design and Implementation of a Novel Directional Coupler for UHF RFID Reader

The directional coupler is applied to isolating RX from TX because of low cost and simplicity compared to the circulator in the radio-frequency identification (RFID) reader. Because of unequal phase velocity between odd and even mode, the drawback of the traditional microstrip directional coupler is poor isolation. In this paper, to obtain a good isolation between RX and TX, a novel directional coupler is proposed to be applied to the UHF RFID system with a single antenna. Measurement result shows that the proposed directional coupler possesses a good isolation of -35dB in operating frequency band.

Design of Koch Fractal Circularly Polarized Antenna for Handheld UHF RFID Reader Applications

In this study, a novel design of circularly polarized antenna based on Koch fractal geometry is presented and experimentally investigated. Circular polarization and size reduction are achieved by placing two asymmetric Koch fractal geometries on x-and y-planes of the single-probe feed square radiator. Further, to tune resonant frequency around the 911MHz, four arrow-shaped slots are inserted in diagonal axes of the square radiator. It is perceived that compact size of the antenna can be achieved by increasing the overall size of the arrow-shaped slots and indentation angles of Koch fractal geometry. The antenna is fabricated on FR4 substrate with a size of 54 × 54 × 1.6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (0.162λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.162λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.0048λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> at 900 MAbstract-In this study, a novel design of circularly polarized antenna based on Koch fractal geometry is presented and experimentally investigated. Circular polarization and size reduction are achieved by placing two asymmetric Koch fractal geometries on xand y-planes of the single-probefeed square radiator. Further, to tune resonant frequency around the 911MHz, four arrow-shaped slots are inserted in diagonal axes of the square radiator. It is perceived that compact size of the antenna can be achieved by increasing the overall size of the arrow-shaped slots and indentation angles of Koch fractal geometry. The antenna is fabricated on FR4 substrate with a size of 54 × 54 × 1.6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (0.162λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.162λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.0048λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> at 900 MHz) and tested to validate the proposed design. The 3-dB axial-ratio bandwidth and impedance bandwidth of the proposed antenna design are found to be 8 MHz (907.0-915 MHz) and 37.0 MHz (891.0-928.0 MHz), respectively. The measured results confirm that the proposed design covers US radio-frequency identification (RFID) band (902-928 MHz) and can be used for RFID short-range reading applications.Hz) and tested to validate the proposed design. The 3-dB axial-ratio bandwidth and impedance bandwidth of the proposed antenna design are found to be 8 MHz (907.0-915 MHz) and 37.0 MHz (891.0-928.0 MHz), respectively. The measured results confirm that the proposed design covers US radio-frequency identification (RFID) band (902-928 MHz) and can be used for RFID short-range reading applications.

Temperature increase in the fetus exposed to UHF RFID readers.

Exposure to electromagnetic fields (EMFs) has prominently increased during the last decades due to the rapid development of new technologies. Among the various devices emitting EMFs, those based on Radio-frequency identification (RFID) technologies are used in all aspects of everyday life, and expose people unselectively. This scenario could pose a potential risk for some groups of the general population, such as pregnant women, who are expected to be possibly more sensitive to the thermal effects produced by EMF exposure. This is the first paper that addresses the estimation of temperature rise in two pregnant women models exposed to ultrahigh frequency RFID by computational techniques. Results show that the maximum temperature increase of the fetus and of the pregnancy-related tissues is relatively high (even about 0.7°C), not too far from the known threshold of biological effects. However, this increase is confined to a small volume in the tissues.

Hardware Design of UHF RFID Reader for the Internet of Things

Internet of Things is a key component of next generation information technology. And Radio-frequency identification (RFID) is one of the key technologies of Internet of Things. RFID technology is widely used for supply chain management and inventory control. Furthermore, RFID has been recognized as a tool to realize a ubiquitous environment. This paper introduces a complete solution of UHF RFID reader system based on LPC1768 microprocessor and AS3992 UHF Reader chip for the Internet of Things. The UHF RFID reader uses the MCU chip of LPC1768 as main controller, which provides excellent multimedia performance. This reader uses AS3992 UHF RFID reader chip, which conforms to ISO18000-6B and ISO18000-6C (EPC global class 1 gen 2) standards. The operating frequency is 840~960MHz, which can be adjustable by users. This paper gives the complete hardware design of the UHF RFID reader.

Item-Level RFID Tag Location Sensing Utilizing Reader Antenna Spatial Diversity

A robust estimation procedure for sensing the locations of passive UHF radio frequency identification (RFID) tags is introduced based on spatial deployment of the reader antennas for maximum signal diversity. A signal model is developed for the received signal strength indicator seen by each reader antenna and incorporated into a mean-square error testing function. The error function is minimized at each test point in the interrogation zone to find the point with the minimum mean-square error. The minimization is independent of the tag type and orientation, making the proposed method very robust compared with other methods that are based on reference tags and radio maps. Experimental results are presented for a realistic retail scenario with multiple tagged items achieving an estimation accuracy of 35 cm. The location sensing system uses conventional UHF RFID readers, antennas, and passive tags, providing additional capability to existing item-level RFID systems. This added value will help to offset the high cost of large-scale RFID infrastructure development.

An UHF RFID Energy-Harvesting System Enhanced by a DC-DC Charge Pump in Silicon-on-Insulator Technology

An RF-DC converter enhanced by a DC-DC voltage booster in silicon-on-insulator technology for UHF radio frequency identification (RFID) energy harvesting is presented in this letter. When the received RF power level is -14 dBm or higher, the system, fabricated on an FR4 substrate using off-the-shelf low-cost discrete components and connected to a flexible dipole antenna, is able to produce 2.4 V DC voltage to power general-purpose electronic devices. As a simple proof of concept, a device comprising microcontroller, temperature sensor, and EEPROM is considered in this work. The experimental results demonstrate the capability of the system to autonomously perform temperature data logging up to a distance of 5 m from a conventional UHF RFID reader used as an RF energy source.

Interoperation of an UHF RFID Reader and a TCP/IP Device via Wired and Wireless Links

A main application in radio frequency identification (RFID) sensor networks is the function that processes real-time tag information after gathering the required data from multiple RFID tags. The component technologies that contain an RFID reader, called the interrogator, which has a tag chip, processors, coupling antenna, and a power management system have advanced significantly over the last decade. This paper presents a system implementation for interoperation between an UHF RFID reader and a TCP/IP device that is used as a gateway. The proposed system consists of an UHF RFID tag, an UHF RFID reader, an RF end-device, an RF coordinator, and a TCP/IP I/F. The UHF RFID reader, operating at 915 MHz, is compatible with EPC Class-0/Gen1, Class-1/Gen1 and 2, and ISO18000-6B. In particular, the UHF RFID reader can be combined with the RF end-device/coordinator for a ZigBee (IEEE 802.15.4) interface, which is a low-power wireless standard. The TCP/IP device communicates with the RFID reader via wired links. On the other hand, it is connected to the ZigBee end-device via wireless links. The web based test results show that the developed system can remotely recognize information of multiple tags through the interoperation between the RFID reader and the TCP/IP device.

Design and Implementation of the RF Front-End All-Digital Phase-Locked Loop in the UHF RFID Reader

PLL is an important part of the RF front-end module,its performance is directly related to stability and accuracy of the RF base-band signal extracted. A FPGA-based all-digital PLL is implemented in this thesis, Hilbert digital phase detector (HDPD) ,Numerically controlled oscillator (NCO) and FIR digital loop filter module implemented using Verilog language ensure accuracy and stability to Sample input Baseband signal modulated. The experiments confirmed that the all-digital PLL designed in this thesis can overcome the defects of DPLL based on semi-analog circuits; and has high Operating frequency, exact capture time, precision adjustable, simple interface, and so on; can be widely used in radio frequency identification (RFID) and automatic control system.

Module Integrated Antenna With Circular Polarization for Mobile UHF RFID Reader

A module integrated antenna with circular polarization for a mobile UHF radio frequency identification reader is presented. In the proposed design, a reader module using a hybrid assemble technique is directly integrated inside the antenna. In order to compensate the degraded radiation efficiency of the reader antenna due to the module integration, a quadruple inverted-f antenna (QIFA), a type of four-port antenna like QIFA, is used. For the compact four-port antenna, we analyze the optimum matching method considering both the reflection coefficient at each port and the mutual coupling among ports simultaneously to improve the performance of the proposed module integrated antenna. Experimental results show that the proposed module integrated antenna of size 80 × 80 × 11.2 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> with the shielded module is well matched, and has the peak gain of 3.3 dBic and the axial ratio under 2.5 dB.

Compact Microstrip RFID Tag Antenna Mountable on Metallic Objects

This paper presents a compact microstrip antenna that can be attached to a metallic object to form a passive radio frequency identification (RFID) tag operating in the UHF band. The proposed antenna was etched on an FR4 substrate with an overall size of 60mm×45mm×1.6mm, and it consists of a matching network, two radiating patches, and a ground plane. Each patch was extended using a meandered strip and was shorted to the ground plane via four metalized via holes to form a planar inverted-F antenna (PIFA). When mounted on a 50×50cm2 copper plate, the proposed antenna provided a 10-dB impedance bandwidth of 37MHz (901∼938MHz) and a power transmission coefficient (PTC) of 0.86 at a frequency of 915MHz. Moreover, the maximum reading range of the prototype metallic RFID tag, measured using an UHF RFID reader system, reached about 6.2 m at 4-W EIRP radiation power.

A fully integrated UHF RFID reader SoC for handheld applications in the 0.18 μm CMOS process

A low cost fully integrated single-chip UHF radio frequency identification (RFID) reader SoC for short distance handheld applications is presented. The SoC integrates all building blocks—including an RF transceiver, a PLL frequency synthesizer, a digital baseband and an MCU—in a 0.18 μm CMOS process. A high-linearity RX front-end is designed to handle the large self-interferer. A class-E power amplifier with high power efficiency is also integrated to fulfill the function of a UHF passive RFID reader. The measured maximum output power of the transmitter is 20.28 dBm and the measured receiver sensitivity is −60 dBm. The digital baseband including MCU core consumes 3.91 mW with a clock of 10 MHz and the analog part including power amplifier consumes 368.4 mW. The chip has a die area of 5.1 × 3.8 mm2 including pads.

A low cost miniaturized circularly polarized antenna for UHF radio frequency identification reader applications

AbstractA low cost miniaturized CP antenna is proposed for UHF RFID (Radio Frequency Identification) reader applications. The antenna is composed of a vertical ground and a square‐ring patch with truncated corners. A novel capacitively coupled feed structure is proposed for good impedance matching. The antenna has S11 &lt; −20 dB and a gain level of about 6.9 dBi at 920–925 MHz (Chinese RFID band). Comparing to the conventional CP antenna, the size of the proposed antenna can be reduced by 33%. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2382–2384, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24612

Range Correlation Effect on the Phase Noise of an UHF RFID Reader

Phase noise is an important parameter in designing radio frequency (RF) systems since it can have large influence on system performance. Especially in RF identification (RFID) systems, phase noise is significantly reduced by the range correlation effect. Therefore the range correlation effect on the phase noise should be carefully considered in analyzing system performance and/or determining required phase noise specification. In this letter, the performance of an ultra high frequency RFID reader under phase noise and its dependence on the presence or absence of the range correlation effect are analyzed.

A high isolated coupled‐line passive circulator for UHF RFID reader

AbstractA coupled‐line passive circulator is proposed for improving the TX/RX isolation of the UHF radio frequency identification (RFID) reader. The increased isolation is realized by generating and adding the canceling signal to the leakage. The input return loss of the reader antenna, which can degrade TX‐to‐RX isolation, as well as the inherently imperfect isolation characteristic of a coupled‐line directional coupler, are included in the design of the coupled‐line passive circulator. The proposed coupler exhibits up to 60‐dB isolation characteristic with the mismatch of the employed reader antenna. The performance comparison between the proposed and the conventional coupled‐line directional couplers shows a significant improvement in the leakage‐to‐signal ratio by up to 35 dB. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2597–2600, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23705