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Use of electronic animal identification technologies by livestock managers is increasing, but performance of these technologies can be variable when used in livestock production environments. This study was conducted to determine whether 1) read distance of low-frequency radio frequency identification (RFID) transceivers is affected by type of transponder being interrogated; 2) read distance variation of low-frequency RFID transceivers is affected by transceiver manufacturer; and 3) read distance of various transponder-transceiver manufacturer combinations meet the 2004 United States Animal Identification Plan (USAIP) bovine standards subcommittee minimum read distance recommendation of 60 cm. Twenty-four transceivers (n = 5 transceivers per manufacturer for Allflex, Boontech, Farnam, and Osborne; n = 4 transceivers for Destron Fearing) were tested with 60 transponders [n = 10 transponders per type for Allfiex full duplex B (FDX-B), Allfiex half duplex (HDX), Destron Fearing FDX-B, Farnam FDX-B, and Y-Tex FDX-B; n = 6 for Temple FDX-B (EM Microelectronic chip); and n = 4 for Temple FDX-B (HiTag chip)] presented in the parallel orientation. All transceivers and transponders met International Organization for Standardization 11784 and 11785 standards. Transponders represented both one-half duplex and full duplex low-frequency air interface technologies. Use of a mechanical trolley device enabled the transponders to be presented to the center of each transceiver at a constant rate, thereby reducing human error. Transponder and transceiver manufacturer interacted (P < 0.0001) to affect read distance, indicating that transceiver performance was greatly dependent upon the transponder type being interrogated. Twenty-eight of 30 combinations of transceivers and transponders evaluated met the minimum recommended USAIP read distance. The mean read distance across all 30 combinations was 45.1 to 129.4 cm. Transceiver manufacturer and transponder type interacted to affect read distance variance (P < 0.05). Maximum read distance performance of low-frequency RFID technologies with low variance can be achieved by selecting specific transponder-transceiver combinations. Key words: cattle, electronic identification, transceiver, transponder doi: 10.2527/jas.2009-2070

In this paper, we describe a UHF radio-frequency-identification tag test and measurement system based on National Instruments LabVIEW-controlled PXI RF hardware. The system operates in 800-1000-MHz frequency band with a variable output power up to 30 dBm and is capable of testing tags using Gen2 and other protocols. We explain testing methods and metrics, describe in detail the construction of our system, show its operation with real tag measurement examples, and draw general conclusions. Index Terms--Radio-frequency identification (RFID), tags, testing and measurement.

This paper proposes an efficient method for localization and pose estimation for mobile robot navigation using passive radio-frequency identification (RFID). We assume that the robot is able to identify IC tags and measure the robot's pose based on the relation between the previous and current location according to the IC tags. However, there arises the problem of uncertainty of location due to the nature of the antenna and IC tags. In other words, an error is always present which is relative to the sensing area of the antenna. Many researches have used external sensors in order to reduce the location errors, with few researches presented involving purely RFID driven systems. Our proposed algorithm that uses only passive RFID is able to estimate the robot's location and orientation more precisely by using trigonometric functions and the IC tags' Cartesian coordinates in a regular gridlike pattern. The experimental results show that the proposed method effectively estimates both the location and the pose of a mobile robot during navigation. Index Terms--Autonomous mobile robot, localization, navigation, passive radio-frequency identification (RFID), pose estimation.

Traceability is a key factor for the agri-food sector. Radio-frequency identification (RFID) technology, which is widely adopted for supply chain management, can be used effectively for the traceability management. In this paper, a framework for the evaluation of a traceability system for the agri-food industry is presented, and the automation level in an RFID-based traceability system is analyzed and compared with respect to traditional ones. Internal and external traceabilities are both considered and formalized, in order to classify different environments, according to their automation level. Traceability systems used in a sample sector are experimentally analyzed, showing that, by using RFID technology, agri-food enterprises increase their automation level and also their efficiency, in a sustainable way. Index Terms--Agri-food sector, radio-frequency identification (RFID), traceability management.

This paper presents a novel radio-frequency identification (RFID)-based smart freezer using a new inventory-management scheme for extremely low temperature environments. The proposed solution utilizes backpressure inventory control, systematic selection of antenna configuration, and antenna power control. The proposed distributed-inventory-control (DIC) scheme dictates the amount of items transferred through the supply chain. When a high item visibility is ensured, the control scheme maintains the desired level of inventory at each supply-chain echelon. The performance of the DIC scheme is guaranteed using a Lyapunov-based analysis. The proposed RFID antenna-configuration design methodology coupled with locally asymptotically stable distributed power control ensures a 99% read rate of items while minimizing the required number of RFID antennas in the confined cold chain environments with non-RF-friendly materials. The proposed RFID-based smart-freezer performance is verified through simulations of supply chain and experiments on an industrial freezer testbed operating at -100[degrees]F. Index Terms--Inventory control, low-temperature chemical management, passive radio-frequency identification (RFID), power control.

In this paper, the effects of ultrahigh-frequency band passive radio-frequency identification (RFID) reader-to-reader interference are investigated in terms of the interrogation range. A reader-to-reader interference model based on interference statistics is proposed, and the nominal interrogation range of a desired reader is derived by this model. In order to evaluate the RFID reader-to-reader interference quantitatively, the interrogation-range-reduction ratio (IRRR) is also defined. For a simple case with only one interfering reader, the analytic and experimental results are in good agreement. Reader-reader distance achieving 0% IRRR, indicating no interference between the readers, is 1200 m for the multiple-reader environment. Additionally, IRRR values are calculated in various environments according to the North American and Korean regulations. The maximum number of allowable interfering readers is then calculated by the proposed interference model and a target IRRR. Index Terms--Interrogation-range-reduction ratio (IRRR), reader-to-reader interference, ultrahigh-frequency (UHF) radio-frequency identification (RFID).

This paper presents a fully integrated CMOS analog front end for a passive 900-MHz radio-frequency identification (RFID) transponder. The power supply in this front end is generated from the received RF electromagnetic energy by using an RF-dc voltage rectifier. In order to improve the compatibility with standard CMOS technology, Schottky diodes in conventional RF-dc rectifiers are replaced by diode-connected MOS transistors with zero threshold. Meanwhile, theoretical analyses for the proposed rectifier are provided and verified by both simulation and measurement results. The design considerations of the pulsewidth-modulation (PWM) demodulator and the backscatter modulator in the front end are also discussed for low-power applications. The proposed front end is implemented in a 0.35-[micro]m 2P4M CMOS technology. The whole chip occupies a die area of 490 x 780/[micro][m.sup.2] and consumes only 2.1 [micro]W in reading mode under a self-generated 1.5-V supply voltage. The measurement results show that the proposed rectifier can properly operate with a -14.7-dBm input RF power at a power conversion efficiency of 13.0%. In the proposed RFID applications, this sensitivity corresponds to 10.88-m communication distance at 4-W equivalent isotropically radiated power from a reader base station. Index Terms--Backscatter modulation, charge pump, low power, low voltage, pulsewidth modulation (PWM), radio-frequency identification (RFID), rectifier, RF--dc, zero-threshold.

This paper presents a new CMOS integrated analog front-end circuit for 13.56-MHz radio-frequency identification tags. The proposed analog front end consists of a novel CMOS rectified voltage multiplier, a voltage regulator, and a new frequency-shift keying (FSK) demodulator. The proposed single-stage rectifier employing only a PMOS/NMOS pass transistor, an inverter, and one capacitor gets minimal active area and enhances the power conversion efficiency. Moreover, a new technique is used in the proposed FSK demodulator, which includes the data recovery circuit, the multiplexer, the shift register, the phase frequency detector, and the charge-pump circuit. The analog front end has been fabricated in a CMOS 0.35-[micro]m 2P4M technology. The demodulator circuit supports a data rate of 10 kb/s to 1 Mb/s. The power consumption is as low as 0.96 mW, and the chip area without pads is only 0.74 mm x 0.43 mm. Experimental results show that the proposed analog front end works well and confirms the theoretical analysis. Index Terms--Frequency-shift keying (FSK) demodulator, radio-frequency identification (RFID), rectifier, regulator, voltage multiplier.

We present a fully integrated long-range UHF-band passive radio-frequency-identification tag chip fabricated in 0.35-[micro]m CMOS using titanium (Ti/Al/Ta/Al)-silicon Schottky diodes. The diodes showed low turn-on voltages of 95 and 140 mV for diode currents of 1 and 5 [micro]A, respectively. In addition, the Schottky diodes exhibited low-resistive loss, and a high-Q-factor design approach was exploited to achieve a long read range for the tag integrated circuit (IC). An optimized voltage multiplier resulted in an excellent sensitivity of -14.8 dBm and corresponding power-conversion efficiency of 36.2% for generating an output voltage of 1.5 V at 900 MHz. The range analysis of the measured multiplier performance indicated an operating range of more than 9 m at 4-W Effective Isotropically Radiated Power reader power. The subthreshold-mode operation of an ASK demodulator allowed ultralow power operation. Under power consumption as low as 27 nW, the demodulator supported a data rate of 150 kb/s and a modulation depth of 40%. A new architecture for generating a stable system clock (2.2 MHz) for the tag IC was employed to deal with supply voltage and temperature variations. Measurements showed that the clock generator had an error of 0.91% from the center frequency owing to an 8-b digital calibration scheme. Index Terms--ASK demodulator, oscillator with calibration, radio-frequency identification (RFID), Schottky diodes, voltage multiplier.

In parallel with the proliferation of radio-frequency identification (RFID) systems, many RFID readers have been increasingly employed. In such an environment, collision among readers becomes a serious problem. Existing anticollision algorithms, depending on the information of neighboring readers, may require constant effort in order to grasp such information. Although it may be given by a server or a coordinator, they may not be suitable in dense and dynamic RFID networks with mobile readers. In this paper, we propose an efficient reader anticollision algorithm using a polling server in dense and dynamic RFID networks with mobile readers. Owing to the assistance of the server, the readers can rapidly decide whether they can work or not without interfering neighbors and can be easily synchronized. Our proposed algorithm is simple and makes readers aware of neighbors to minimize reader collisions. Performance evaluation shows how many readers can operate in a network and indicates that our proposed algorithm is more efficient than distributed color selection, colorwave, and hierarchical Q-learning algorithm, particularly in dense and mobile environments. Index Terms--Anticollision, dense radio-frequency identification (RFID) networks, mobile readers, server, tags.

The performance of an ultra-high-frequency RF identification (ID) system operating at 869 MHz, intended for the ID of persons in both indoor and open areas, has been validated using the propagation models, as well as the series of practical measurements. A two-ray propagation model and the 3-D ray-tracing model were used for calculations of all important system parameters in open and indoor areas, respectively. For the application mentioned above, a novel (electrically small and, at the same time, low-profile) wearable TAG antenna was designed. It was used in order to carry out the necessary tests as well. The antenna in question is based on an artificial-like surface. The latter provides an important screening effect and avoids detuning. Another virtue of the surface used is represented by the fact that it ensures the minimum loss of the antenna efficiency (resulting from the presence of a nearby human body). The simulations and measurements show that the optimized system can guarantee a reliable ID at distances up to 9 m in open areas and up to 16 m in corridors. Index Terms--Artificial surface, electrically small antenna, identification (ID) of people, loop antenna, RF identification (RFID) system, TAG antenna.

In this paper, we present the extension of a recently published two-frequency continuous-wave (CW) ultra-high-frequency RF identification ranging technique to multiple carriers. The proposed system concept relies on exact phase information; hence, the passive tag cannot be accurately modeled as a frequency-flat linear device. A linearized model of the tag's reflection coefficient is devised to bridge the gap between the nonlinear reality and the linear CW radar theory. Estimation error bounds are derived and effects caused by noise and multipath propagation are analyzed in detail. It has been found that systematic errors introduced by the tag's reflection characteristic cannot be compensated by using multiple carriers due to large variations caused by detuning. Nonetheless the system, while being vulnerable to multipath propagation effects, still performs well under line-of-sight conditions; mean average errors below 15% of the true distance are possible in typical fading environments. Index Terms--Continuous-wave (CW) radar, detuning, multipath channel, narrowband, ranging, system modeling, ultra-high-frequency (UHF) RF identification (RFID).

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. Index Terms--Battery assisted, EPCGlobal, multipath fading, passive tag, read range, RF identification (RFID), ultra high frequency (UHF).

A fully passive printable chipless RFID system is presented. The chipless tag uses the amplitude and phase of the spectral signature of a multiresonator circuit and provides 1 : 1 correspondence of data bits. The tag comprises of a microstrip spiral multiresonator and cross-polarized transmitting and receiving microstrip ultra-wideband disc loaded monopole antennas. The reader antenna is a log periodic dipole antenna with average 5.5-dBi gain. Firstly, a 6-bit chipless tag is designed to encode 000000 and 010101 IDs. Finally, a 35:bit chipless tag based on the same principle is presented. The tag has potentials for low-cost item tagging such as banknotes and secured documents. Index Terms--Antenna, chipless RF identification (RFID), cross-polarization, multiresonator, reader, transponder, ultra-wideband (UWB).

In this paper, the feasibility of inkjet printing of circuit and microwave structures on paper-based substrates is investigated for the first time in the implementation of a complete low-cost wireless platform for sensors. First, the system-level design of the module including the amplifier characterization were carried out to ensure optimum performance of the sensor modules in the UHF bands used in RF identification communication. These results were then used to design two different antenna structures, which are printed on paper along with their respective circuit layouts using inket-printing technology. Different techniques were investigated for the assembly of circuit components on the silver printed layouts. Finally, wireless link measurements on the assembled prototypes verified the good performance on the wireless and sensing sides. Index Terms--Antenna, assembly, dipole, inkjet printing, micro-controller, monopole, paper, power amplifier (PA), RF identification (RFID), sensor, temperature, transmitter, ultra high frequency (UHF), wireless.

A novel low-profile bow-tie patch antenna, which can be mounted on metallic objects for RF identification (RFID) applications is presented. This antenna is fabricated using a single layer printed circuit board with thickness of 1.5 mm without any via-hole or shorting plate. The RFID chip is connected to a small loop, which is magnetically coupled to the radiating body. The loop, as well as the radiating body, can be fabricated as a separate inlay, simplifying the manufacturing process and reducing its cost. A prototype has been fabricated and measured. Index Terms--Antenna, metal, patch, RF identification (RFID).

The problems of RF identification are discussed. It is shown that the use of passive transponders is preferable, but weak energy of the system in this case reduces the operation distance and decreases the noise immunity of the system. In this paper, it is proposed to use the homodyne method of selecting the useful signal. This solution allows to increase the energy and the noise immunity of the system (the operation distance is increased). Furthermore, the interrogator can treat several transponders simultaneously. Index Terms--Homodyne detection, microwave phase shifter, modulator, transponder.

This paper presents a full duplex active RF identification system with arbitrary values for any of the two frequencies in the different radio links. First, the antennas proposed in this paper are based on linearly polarized self-diplexed patch antennas working in a full-duplex way at 2.45 GHz for the reader-transponder (or tag) link and at a lower variable frequency (1.7 GHz) for the transponder-reader link reducing the propagation losses for the most critical link. Secondly, in order to reduce the multipath losses, antennas with circular polarizations for the reader and linear polarization for the transponder have been designed for the corresponding radio links. Patch antennas partially filled with metamaterial cells have offered the possibility of achieving multifrequency performance with two dipolar radiation modes, one due to the patch and the other to the metamaterial cells. This fact makes it possible to obtain high isolation levels between different ports. In addition, the inclusion of coupled or slot lines to feed the antenna has increased this isolation level. Finally, the diplexing level has been increased by including some filtering lines with metamaterial particles at the input of the feeding fine. This approach avoids using an external filter or diplexer. Index Terms--Left-handed (LH) metamaterials, microstrip antennas, RF identification (RFID) antennas, self-diplexed multifrequency antennas.

A novel front-end structure for ultra-high-frequency RF identification reader is proposed. The proposed front-end consists of a balanced coupler and four-port feed antenna system. The proposed balanced coupler structure has high transmit/receiver isolation feature and good insensitivity to load variations. The proposed four-port feed antenna system is applied for removing the coupling among antennas, which deteriorates the isolation. The proposed system is numerically analyzed and verified experimentally as well. Index Terms--Antenna isolation, directional coupler, load impedance variation, ultra-high-frequency (UHF) RF identification (RFID).