Ultra-high Frequency Near-field Radio Frequency Identification Research Articles

A Novel Near-Field UHF RFID Reader Array Antenna for Configurable Electrically Large Reading Area

In this paper, a novel configurable loop array antenna based on resonator-loaded microstrip lines (RLML) is proposed to enlarge the interrogation zone of the reader antenna for near-field ultrahigh-frequency (UHF) radio frequency identification (RFID) system. The proposed loop array antenna is composed of a number of RLML loop units. By configuration of the RLML loop units sharing a common side with its adjacent RLML loop units which carry reverse-direction flowing current in the ${x}$ -axis and ${y}$ -axis directions, loop array antennas are created to generate a strong and uniform magnetic-field distribution over a large configurable interrogation area. As an example, loop array antennas with $1\,\times \,8$ and $2\,\times \,3$ RLML loop units implemented onto a piece of an FR4 printed circuit board (PCB) are designed, fabricated, and measured. The measured bandwidth ranges from 894 to 964 MHz for a $1\times 8$ array antenna with a reading area of $570 \,\,{\mathrm{ mm}}\times 150\,\,{\mathrm{ mm}}$ and 917–932 MHz for a $2\times 3$ array antenna with a reading area of $270 \,\,{\mathrm{ mm}}\times 240\,\,{\mathrm{ mm}}$ . The reading distances of an $1\times 8$ array antenna for loop-like tag, dipole-like tag, and antimetal tag are achieved up to 22, 42, and 45 mm, respectively. For a $2\times 3$ array antenna, the reading distances of three tags are achieved up to 23, 43, and 40 mm.

A Novel Printed Dual-Log-Periodic Array Antenna for UHF Near-Field RFID Applications

A novel printed center-fed dual-log-periodic array antenna is proposed for ultrahigh frequency (UHF) radio frequency identification (RFID) applications. The proposed antenna is composed of two reversed wideband printed log-periodic dipole array antennas. Two closely spaced oppositely directed currents are thus introduced to achieve intensive and uniform magnetic fields in the near-field zone. A prototype antenna is fabricated and measured in practical application environment. The measurement results agree well with the simulations, and demonstrate that the proposed antenna is suitable to be implemented in RFID systems. The operated frequency band of the antenna is 824–953 MHz (14.5%), covering the UHF band in China, the Federal Communications Commission band, and the European Telecommunications Standards Institute band. With the proposed printed dual-log-periodic array antenna, measurement results also show that the RFID system delivers a 100% guaranteed reading rate within 2.0 cm and a maximum reading range of 19.0 cm.

A Directional, Closely Spaced Zero-Phase-Shift-Line Loop Array for UHF Near-Field RFID Reader Antennas

A zero-phase-shift-line (ZPSL) loop array with two closely spaced elements is proposed to achieve a directional distribution for ultrahigh frequency (UHF) near-field radio frequency identification (RFID) applications. The proposed array consists of two coaxially positioned ZPSL loop antenna elements of the same size, with an aperiodic ZPSL loop acting as a driven element and a periodic ZPSL loop functioning as a parasitic element. A directional magnetic field distribution can be achieved when an out-of-phase current along the parasitic loop is induced. A ZPSL loop array prototype with an interelement spacing of 15 mm, or 0.046 of the operating wavelength at 915 MHz, achieves a desired directional magnetic field distribution over a circular interrogation zone with a diameter of 160 mm. As a UHF near-field RFID reader antenna, the proposed array is able to achieve a 100% detection rate of SAG tags up to 120 mm by using an Impinj Speedway reader with an output power of 30 dBm.

A Grid-Shaped Microstrip Traveling Wave Antenna With Selective Differential Feeding Networks for CM-Level Position Detection Systems

In this paper, a near-field ultrahigh-frequency radio frequency identification (RFID) system, which has cm-level 2-D positioning precision, is proposed. The system consists of a grid-shaped microstrip traveling wave antenna (TWA) and four-port switched differential feeding networks. To selectively form tag-read sections, opposite directional currents (ODCs) are used. To introduce a microstrip TWA for cm-level 2-D positioning, the influence of $H_{z}$ fields in microstrip TWAs is theoretically analyzed. In addition, to utilize field reinforcement and achieve precise 2-D localization, a grid-shaped microstrip TWA with four-port selective switched differential feeding networks is proposed and investigated. The proposed antenna and feeding network were fabricated on FR-4 substrates. The simulated and measured results demonstrate that precise 2-D tag positioning is achieved using the proposed system utilizing ODC along two selected adjacent microstrip lines in the TWA.

Multiobjective Optimization Design for Electrically Large Coverage: Fragment-Type Near-Field\/Far-Field UHF RFID Reader Antenna Design

The design of an ultrahigh-frequency (UHF) radio-frequency identification (RFID) reader antenna covering an electrically large near-field area is challenging for near-field UHF RFID applications. In such a design, magnetic field distribution on a large coverage area is required to be as uniform as possible. For some specific UHF near-field RFID applications, given radiation pattern characteristics are expected. A fragment-type wire structure is quite suitable for these demands because uniform magnetic field distribution and given patterns could be generated through optimizing the fragmented wires in a designated electrically large area to obtain corresponding current distribution. In this article, the concept of a fragment-type structure as well as some design guidelines are reviewed and summarized. Then, two omnidirectional fragment-type wire antennas with different cell size and two directional fragment-type wire antennas are designed. Both simulation and experiment results show that there is no reading null within an electrically large near-field zone having a perimeter of four operating wavelengths at 915 MHz (i.e., 320 mm x 320 mm). The omnidirectional designs are promising in the applications of UHF near-field RFID tag detection in self-confined volumes, and the directional designs are potential in the systems of UHF near-field/far-field RFID.

Review of Zero-Phase-Shift-Line Loop Antennas for UHF Near-Field RFID Readers

The design of electrically large loop-type antennas for ultra-high frequency (UHF) near-field radio frequency identification (RFID) readers is a challenge due to the inherent limitation of loop type antennas. This paper reviews the development of the zero-phase-shift-line (ZPSL) loop antennas for UHF near-field RFID systems. First, the state-of-the-art ZPSL loop antennas are briefed and then the modeling of the ZPSL structures is introduced. After that, some typical electrically large ZPSL loop antennas for UHF near-field RFID readers are demonstrated, including single-loop antenna, dual-loop antenna, grid loop array antenna, and artificial magnetic conductor backed directional loop antenna. All the patentable works have been applied for industry applications.

Design of a Near-Field Nonperiodic Zero Phase Shift-Line Loop Antenna With a Full Dispersion Characterization

The tradeoff between the magnetic field distribution, the magnetic field intensity, and the interrogation zone size is one of the most challenging issues in designing a zero phase shift-line (ZPSL) loop antenna for near-field ultrahigh-frequency radio frequency identification (RFID) applications. In this communication, the dispersion characteristics, including phase and attenuation constants, of the ZPSL in a loop configuration are thoroughly analyzed, such that the important design tradeoff can be fully quantified. Based on the dispersion characteristics, a nonperiodic ZPSL loop antenna with nonuniformly arranged unit cells is proposed. Compared with the periodic configurations, the proposed nonperiodic ZPSL loop antenna shows an improved magnetic field distribution with an enhanced magnetic field intensity.

A Novel UHF Near-Field RFID Reader Antenna Deploying CSRR Elements

A novel ultrahigh frequency (UHF) near-field radio-frequency identification (RFID) reader antenna based on the complementary split ring resonator (CSRR) elements is presented in this communication. The antenna consists of a power divider and two arms. The two arms are terminated with two 50- $\Omega $ terminations. First arm is forward arm, which is a microstrip transmission line. The second arm is backward arm, which is loaded with CSRR elements, instigating backward wave propagation. The oppositely directed currents are generated by this configuration to produce strong and uniform magnetic field over the antenna plane for UHF near-field RFID operations. The proposed antenna operates from 0.76 to 0.88 GHz, and a total impedance bandwidth of 120 MHz is obtained. A near-field read range of 100 mm and an interrogation area of 220 mm $\times180$ mm over the antenna plane at a height of 50 mm is reported for this antenna.

A Yagi–Uda Antenna With Load and Additional Reflector for Near-Field UHF RFID

In this letter, a Yagi–Uda antenna with load and additional reflector is proposed to achieve strong and uniform magnetic field distribution within the antenna area for near-field ultrahigh-frequency radio frequency identification (RFID). This proposed antenna is composed of one driven dipole to emit electromagnetic (EM) wave, several directors to direct the EM wave to the desired area, a load element at the end of the director array to absorb the wave, and two reflectors at both ends to reflect the EM wave. The proposed antenna can generate a uniform magnetic field distribution within the antenna area, meanwhile keeping the field strength outside the antenna area relatively small. A prototype, as an example, that contains 13 elements is designed and fabricated, with the measured bandwidth of 880–980 MHz. The achieved interrogation area is 440 × 160 mm2, measured by utilizing a commercial RFID reader and some near-field tags. It is worth mentioning that the interrogation area can be extended by adding more directors to the antenna.

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.

Magnetic Tag Antenna for UHF Near-field and Far-Field RFID Applications

A novel broadband magnetic Tag antenna for ultra-high frequency (UHF) near-field (NF) and far-field (FF) radio-frequency identification (RFID) applications is presented. This antenna is printed on an Rogers RT/duroid 5880 substrate with an overall size of 68 × 19.7 × 0.787 mm. The simulated bandwidth of the proposed Tag antenna is more than 100 MHz (860960MHz), which can cover the entire UHF RFID band. The proposed structure can generate a strong and uniform H-field distribution in the region around the antenna. The minimum power required to activate the Tag at 900 MHz is approximately of -12.6 dBm in the near-zone (18 cm) and 2.8 dBm in the far-zone (65 cm) in anechoic chamber. The measured read range is about 15 m when the transmission power level is 25 dBm in open environment. Measurements show that the antenna operating confirms good performance of Tag identification for near-field and far-field UHF RFID applications.

Novel UHF Near-Field RFID Reader Antenna Based on Double-Sided Parallel-Strip Line

A novel reader antenna based on double-side parallel-strip line (DSPSL) for ultra-high frequency (UHF) near-field radio frequency identification (RFID) systems is proposed. The antenna is composed of a phase inverter, DSPSL structures, and four dipoles. The fabricated antenna works from 887 to 938 MHz with reflection coefficient less than -10 dB. The maximum reading distances are 200 and 70 mm when the input power is 30 and 17 dBm, respectively. Measurement results show that the antenna has good performance in near-field UHF RFID systems.

One terminal improving method of open-circuit near-field antenna of UHF RFID system

A novel broadband dual-loop antenna is presented for the ultra high frequency (UHF) near-field radio frequency identification (RFID) applications. Owing to the novel structure, the current distribution along the loop is kept in phase, as well as the metal terminals exert less influence on the z-orientation magnetic field. The antenna with novel terminals is described and the principle of operation is explained. A comprehensive parametric study of the new model is carried out and the results are presented and discussed in detail. To prove the novel structure, a prototype is developed and fabricated. The measurement results demonstrate that the antenna could achieve a broad bandwidth and low gain, and produce a strong magnetic field with a relatively small z-orientation magnetic field empty hole in the near field. Hence, the work is very promising for UHF near-field RFID reader applications.

Electrically Large Dual-Loop Antenna for UHF Near-Field RFID Reader

An electrically large dual-loop antenna is proposed for ultra high frequency (UHF) near-field radio frequency identification (RFID) readers. The proposed antenna is composed of a main loop and a parasitic loop wherein the loops are constructed using segmented lines with distributed capacitors. The parasitic loop enhances and uniforms the magnetic field distribution in the central portion of the larger main loop so that the perimeter of interrogation zone of the dual-loop antenna can be extended up to three operating wavelengths. The measurement shows that a dual-loop antenna prototype printed onto a piece of FR4 printed circuit board (PCB) achieves good impedance matching over the frequency range of 845-928 MHz and produces strong and uniform magnetic field distribution with an interrogation zone of 250 mm 250 mm. A parametric study is carried out to provide the guidelines for the antenna design.

A Novel Fractal Antenna for UHF Near-Field RFID Readers

This letter accentuates a novel fractal protruded tapered slot (FPTS) antenna and its magnetic field analysis for ultra-high frequency (UHF) near-field (NF) radio frequency identification (RFID) readers. The principle of variable distance opposite direction current (VDODC) is employed here. The antenna operates over a bandwidth of 101 MHz (852-953 MHz) with a center frequency of 897 MHz. The interrogation area of 243 × 190 mm2 is achieved for this antenna at a distance of 50 mm from the plane of the antenna in z-direction. The antenna tested with the presence of different liquids and the performance is evaluated. The field analysis shows that antenna becomes handy over potential applications like tracking chemicals and pharmaceutical management.

An RFID tracking system supporting the behavior analysis of colonial laboratory animals

Animal tracking and animal behavior analysis have a crucial impact in biomedical disciplines to study new pathologies and effects of new drugs. There are several solutions, based on different technologies such as GPS, radar, and vision, designed to obtain animals tracking systems, but they are effective mainly in presence of large size animals and outdoor environment. Unfortunately, they show poor performance when groups of small laboratory animals have to be monitored in indoor environments. In such a context, the adoption of passive Near Field (NF) Ultra High Frequency (UHF) Radio Frequency Identification (RFID) technology seems to be a winning approach, even though the straightforward use of commercial solutions does not guarantee satisfactory performance. Specifically, customized hardware and software solutions are then required. The main goal of this work is to present the development and then to validate a reliable and effective system for the automatic tracking of laboratory mice, based on suited NF UHF RFID hardware capturing system combined with an ad hoc software system able to guarantee hardware control, data processing, and reporting. In particular, the validation phase has been carried out by selecting the most appropriate RFID tags and by surgically implanting them into laboratory mice. Experimental results have demonstrated the efficiency of the proposed solution, which is able to gather data on the animal movements, allowing their subsequent processing for a satisfactory behavioral analysis.

Design of Antenna for UHF Near-Field RFID Reader

A segmented loop antenna is presented for ultra-high frequency (UHF) near-field radio frequency identification (RFID) reader. The segmented antennas have been constructed that can operate at resonant diameters while still providing good magnetic coupling. The antenna printed on a FR4 printed circuit board (PCB) with an overall size of 170× 170 × 1 mm3 achieves good impedance matching and uniform magnetic field distribution over an operating bandwidth of 840–1120 MHz, which is desirable for UHF near-field RFID reader applications.

Study of broadband near-field antenna for ultra-high-frequency radio frequency identification applications

A novel antenna for applications in an ultra-high-frequency (UHF) radio frequency identification (RFID) reader system is proposed and investigated. The antenna achieves a gain of lower than −10 dBi in all directions with strong magnetic field distribution over the entire UHF RFID band of 830–950 MHz as well as good performance in detecting tags when applied in UHF RFID systems. The antenna configuration is described and the principle of operation is explained. To investigate the effects of each parameter on the antenna performance, a comprehensive parametric study is carried out and the results are presented in detail and discussed. To prove the concept, a prototype is developed and fabricated. The measurement results demonstrate that the antenna can achieve a broad bandwidth and low gain, and produce a strong magnetic field with relatively concentrated field distribution in the near-field region of the antenna. Hence, this work is very promising for UHF near-field RFID reader applications.

UHF near-field RFID reader antenna with capacitive couplers

A segmented loop antenna with capacitive couplers is proposed for ultra-high frequency (UHF) near-field radio frequency identification (RFID) applications, which is capable of generating a strong and uniform magnetic field in a near-field zone even though the perimeter of the loop is comparable to the operating wavelength. As an example, an antenna printed onto an FR4 printed circuit board with an interrogation zone of 154 × 154 mm exhibits good impedance matching and uniform magnetic field distribution over an operating bandwidth of 790-1000 MHz, which is desirable for UHF near-field RFID reader applications.

Segmented loop antenna for UHF near-field RFID applications

A segmented loop antenna is presented for ultra-high frequency (UHF) near-field radio frequency identification (RFID) applications. The proposed segmented configuration makes the current along the loop remain in-phase even though the perimeter of the loop is comparable to the operating wavelength, so that a strong and uniform magnetic field is generated in the region surrounding the antenna. The antenna printed on a FR4 printed circuit board (PCB) with an overall size of 160×180×0.5 mm achieves good impedance matching and uniform magnetic field distribution over an operating bandwidth of 800–1040 MHz, which is desirable for UHF near-field RFID reader applications.