Ultra High Frequency Radio Frequency Identification Reader Research Articles

Nature-inspired spider web shaped UHF RFID reader antenna for IoT and healthcare applications

This paper proposes a nature-inspired spider web-shaped ultra-high frequency (UHF) radio frequency identification (RFID) reader antenna and battery-free sensor-based system for healthcare applications. This antenna design consists of eight concentric decagons of various sizes and five straight microstrip lines.These lines are connected to the ground using 50 Omega resistors from both ends, except for one microstrip line that is reserved for connecting a feeding port. The reader antenna design features fairly strong and uniform electric and magnetic field characteristics. It also exhibits wideband characteristics, covering whole UHF RFID band (860–960 MHz) and providing a tag reading volume of 200 times 200 times 20 mm{^3}. Additionally, it has low gain characteristics, which are necessary for the majority of nearfield applications to prevent the misreading of other tags. Moreover, the current distribution in this design is symmetric throughout the structure, effectively resolving orientation sensitivity issues commonly encountered in low-cost linearly polarized tag antennas. The measurement results show that the reader antenna can read medicine pills tagged using low-cost passive/battery-free RFID tags, tagged expensive jewelry, intervenes solution, and blood bags positioned in various orientations. As a result, the proposed reader antenna-based system is a strong contender for near-field RFID, healthcare, and IoT applications.

High Gain Passive UHF RFID Reader Antenna Using Novel FSS for Longer Read Range

Frequency Selective Surface (FSS) is widely used to enhance the gain of antenna & reduces Electromagnetic Interference (EMI). In this work, a novel Frequency Selective Surface (FSS) is designed, analyzed, and fabricated along with passive Radio Frequency Identification (RFID) reader antenna operating at global Ultra-High Frequency (UHF) for wireless RFID applications. The antenna & FSS sheet is fabricated on less costly FR4 substrate with resonant bandwidth of 860–960 MHz. The Fabry–Perot arrangement of FSS sheet with antenna increases the gain & directivity without modifying the antenna profile or increasing radiation patch size. The maximum measured gain is 9.8 dB & 7.2 dB with the Reflection coefficient (S11) of −35 dB & −15 dB at 910 MHz & 950 MHz respectively. The proposed antenna of dimension 40 mm by 40 mm is fabricated & tested for further experimental validation with measured read range longer than 8 m. The novelty in proposed work is integration of FSS with passive UHF RFID technology which can be effectively used in wireless RFID applications for improved read range, higher gain, lower power consumption & better immunity within the resonating band. The proposed antenna effectively isolates out-of-band frequencies from in-band frequencies over a required bandwidth reducing Electromagnetic Interference (EMI) for UHF RFID applications.

Glasses frame‐based wearable antenna design for ultrahigh frequency radio frequency identification and Internet of Things applications using characteristic mode analysis

A novel ultra-high frequency (UHF) radio frequency identification (RFID) passive tag antenna based on a glasses frame is proposed for Internet of Things (IoT) applications. The glasses frame structure is exploited using characteristic mode analysis (CMA) to explore different modes for both 900 MHz and 2.4 GHz frequency bands. The proposed design consists of a glasses metallic frame and a loop for conjugate matching with an RFID chip (Alien Higgs H4). First of all, an already manufactured glasses metal frame structure is simulated in Computer Simulation Technology (CST) Microwave studio using CMA to get CM modes in the required RFID band. After that, a small loop is used along with the RFID chip as a capacitive coupling element to excite modes at 900 MHz by placing it at current minima. Moreover, the proposed tag antenna is also simulated with the voxel head model in CST and there is no significant change in impedance and reflection coefficient. The simulated specific absorption rate (SAR) is 0.5 W/Kg. Furthermore, the tag design is simulated with different glass materials and also with different frame structures to prove the robustness of the proposed solution. This tag design covers the entire US UHF RFID band (902–928 MHz) and features a read range of 2 m, measured using a UHF RFID reader setup with 4 W EIRP. Therefore, this antenna design can be a good candidate for future IoT technologies such as RFID, long range (LoRa), and other IoT applications.

Electromagnetic Assessment of UHF-RFID Devices in Healthcare Environment

In this work, the evaluation of electromagnetic effect of Ultra High Frequency Radio Frequency Identification (UHF-RFID) passive tags used in the healthcare environment is presented. In order to evaluate exposure levels caused by EM field (865–868 MHz) of UHF-RFID readers, EM measurements in an anechoic chamber and in a real medical environment (Hospital Universitario de Canarias), as well as simulations by 3D Ray Launching algorithm, and of biophysical exposure effects in human models are presented. The results obtained show that the EM exposure is localized, in close vicinity of RFID reader and inversely proportional to its reading range. The EM exposure levels detected are sufficient to cause EM immunity effects in electronic devices (malfunctions in medical equipment or implants). Moreover, more than negligible direct effects in humans (exceeding relevant SAR values) were found only next to the reader, up to approximately 30% of the reading range. As a consequence, the EM risk could be firstly evaluated based on RFID parameters, but should include an in situ exposure assessment. It requires attention and additional studies, as increased applications of monitoring systems are observed in the healthcare sector—specifically when any system is located close to the workplace that is permanently occupied.

A Fast Digital Phase Frequency Detector with Preset Word Frequency Searching in ADPLL for a UHF RFID Reader

An All-Digital Phase-Locked Loop (ADPLL) is an architecture that is widely employed in the communication system due to the advancement of the Complementary Metal-Oxide-Semiconductor (CMOS) technology process. A 2.4GHz Radio Frequency Identification (RFID) system needs a frequency synthesizer in the local oscillator architecture of the transceiver to generate a stable frequency tuning range Therefore, in this paper, a Digital Phase-Frequency Detector (DPFD) is designed to achieve the phase and frequency acquisition in the ADPLL system. The proposed DPFD is divided into two main parts, the first is the Phase Detector (PD) and the second is the Frequency Detector (FD). The PD has managed to detect the presence of the phase difference by recognizing two different input signals. The FD, on the other hand, is capable to detect the higher frequency by identifying the output signals from the PD in digital formation. In addition, a control unit module is developed to control and adjust the Preset Word (PW) for the system by using a binary search scheme. Comparison results show that the final value of the PW from the simulation is the same as from the manual calculation (theoretical values). The digital PFD and the PW control modules are designed and simulated by using Verilog HDL code. These two designed modules will be integrated into the targeted ADPLL to achieve fast locking performance and ultra-low power for Ultra-High Frequency (UHF) RFID applications.

A Fully Integrated Passive Self-Jamming Cancellation Architecture with Fast Settling Time for UHF RFID Reader

This paper presents a fully integrated passive self-jamming cancellation (SJC) circuit in 0.18 µm Complementary Metal Oxide Semiconductor (CMOS) technology for ultra-high frequency (UHF) radio frequency identification (RFID) applications. Based on the active amplitude and phase control, a novel passive variable capacitor array and signal combiner are adopted instead of a traditional variable amplifier/attenuator and a phase shifter to reduce the circuit complexity and thus achieve higher linearity and low noise. We use an improved cancellation algorithm based on the local search method to quickly and accurately find the cancellation point that minimizes the self-jamming signal power. The simulation and measurement results are constant, and a suppression of 38 dB can be achieved in the working frequency of 860–960 MHz. The cancellation algorithm can be finished within 0.5 ms. These results indicate that the designed SJC circuit can be a promising candidate for UHF RFID applications.

UHF RFID tag localization using pattern reconfigurable reader antenna.

Passive ultra high frequency (UHF) radio frequency identification (RFID) tags have the potential to find ubiquitous use in indoor object tracking, localization, and contact tracing. We propose a machine learning-based method for RFID indoor localization using a pattern reconfigurable UHF RFID reader antenna array. The received signal strength indicator (RSSI) values (from 10,000 tags) recorded at the reader antenna units are used as features to evaluate the machine learning models with a train-test split of 75%-25%. The training and testing data is generated by a wireless ray tracing simulator. Five machine learning models: random forest regressor, decision tree regressor, Nu support vector regressor, nearest regressor, and kernel ridge regressor are compared. Random forest regressor has the lowest localization error both in terms of average Euclidean distance (AED) and root-mean-square error (RMSE). For random forest regressor, localization error results show that 90% of the tags are within 1 meter of their true position, and 67% are within 50 cm of their true position based on Euclidean distance.

High-Gain Circularly-Polarized Square Patch UHF RFID Reader Antenna Design for Smart Factory Applications

In this paper, a UHF (Ultra High Frequency) RFID (Radio-frequency identification) circular polarization reader antenna is presented. The proposed antenna is a low cost, easy to manufacture UHF RFID reader antenna in the European UHF RFID band. The proposed antenna design employs an air-substrate patch antenna. The antenna size of 250x250x7mm. The proposed antenna works from 850 to 874 and 880 to 893 MHz with return loss less than -10 dB, thus covering the European UHF RFID band. The proposed antenna return loss bandwidth is 37 MHz. The gain of the designed antenna is 7.88 dBi at 867 MHz. Also, with a bandwidth of 864-870 MHz, the axial ratio (AR) is less than 3dB. This means that the antenna has circular polarization at 867 MHz. Each result has been calculated on CST Studio Suite 2020. The antenna recommended for use in smart factory applications promises a good antenna among RFID reader antennas.

Right-Angled V-Shaped Conformal Dual-Patch Antenna Array for RAIN RFID Doorway Portals

This paper presents a conformal ultra-high-frequency (UHF) radio frequency identification (RFID) reader antenna array for doorway portal applications. The dual-patch antenna is only 100 mm wide and right-angled (V-shaped) to fit the corners of a regular portal. Patches are arranged orthogonally to create horizontal and vertical-linearly polarized fields at near-zones and at far-field distances they provide slant-polarized fields. Beam steering is enabled by phase delaying the array elements to enhance the field coverage within the doorway portal. The antenna operates in the European UHF RFID band (865-868 MHz) with a 38 MHz, 10 dB impedance bandwidth. The antenna’s azimuth and elevation half-power beamwidth is 90° and 130°. The azimuth beam is tilted to 35° from the boresight where the gain is peaked at 5.5 dBi. This antenna is low-profile, low-cost and flame retardant and paintable. Inherited properties of the antenna’s substrate make the antenna non-toxic, self-extinguishing, lightweight and highly chemical resistant. The reader antenna is compatible with both RAIN and non-RAIN alliance UHF RFID readers.

Design of a 3D-printable UHF RFID hybrid liquid antenna for biosensing applications

This paper presents a novel 3D-printable polymer-based liquid antenna for radio frequency identification (RFID) in the ultrahigh-frequency (UHF) band. Fused deposition modelling, the most widespread and inexpensive 3D printing technique, is used for printing a substrate including polypropylene (PP) and acrylonitrile butadiene styrene (ABS). An ALN-9762-WRW type RFID tag containing a meander metal antenna is modified and printed with microfluidic channels in the substrate. As an ionic liquid, a saltwater dilution is injected into the microfluidic channels designed via a computer-aided design program. A fabricated hybrid liquid antenna is tested using a 200mW UHF RFID reader with the ISO 18000-6C EPC Gen2 protocol. The sensitivity to liquid antenna radiation is measured at distances of 20–900 mm by varying saltwater dilution’s salinity and conductivity between 0 and 12000 ppm and 0-20000μS, respectively. Besides saltwater, an essential oil, peppermint oil (C62H108O7), is also used for liquid antenna. The absorption, refraction, reflection, and scattering characteristics of the polymer substratum are explored in the estimation method. The essential oil produces a buffer area in the 3D layers, which can change the polarization of the antenna. The designed and fabricated 3D-printed hybrid liquid antenna can be utilized in embedded systems suitable for chemical or biological sensing within perpetual systems such as blood or oil circuits.

A compact wideband circularly polarized quadrifilar antenna with PIFA elements for UHF RFID readers

AbstractIn this paper, a compact circularly polarized quadrifilar antenna with planar inverted-F antenna (PIFA) elements is presented. The proposed antenna consists of four PIFA elements and a Wilkinson divider-based feed network fabricated on FR-4 substrate (ɛr = 4.4, loss tangent = 0.02, thickness = 1.6 mm). The total size of the antenna is 120 × 120 × 13.2 mm3. Impedance matching with a reflection coefficient <−15 dB and an axial ratio (AR) <3 dB are achieved over the global ultra-high frequency (UHF) radio frequency identification (RFID) frequency band and beyond. The realized gain ranges from 2.25 to 3.75 dBic within the frequency band of interest from 860 to 960 MHz with a directional radiation pattern. The proposed antenna is compact, low-cost and extremely wideband in terms of matching and AR compared to state-of-the-art UHF RFID reader antennas.

An Ultra-Rugged UHF RFID Reader Antenna: A New Design for Convention Center Loading Docks [Wireless Corner

At present, the ultrahigh frequency (UHF) radio-frequency identification (RFID) technology is more popular than several other autoidentification (auto-ID) technologies. An ultrarugged UHF RFID reader antenna is made from a concrete substrate that is sandwiched between a stubbed quarterwave radiator and a folded ground plane is proposed for fixed UHF RFID readers. This linearly polarized antenna operates between 865 and 868 MHz with a 3.5-dBi peak gain and a 160-MHz, -15-dB |S11| bandwidth. The 3.5- and 2-dBi gain bandwidth are 80 and 140 MHz, respectively. The antenna is intended to be used in convention center loading docks and is thus tested for extreme environmental conditions, such as temperature, humidity, condensation, and rain as well as the effect of superstrates and metals. More than one concrete tile antenna can be operated by using one RFID reader to realize a distributed antenna system (DAS). The antenna is conformal and can blend with the environment without affecting the existing aesthetics. The antenna creates a wide circumferential read zone (s5.6-m diameter) and reads tags up to 6.5 m at the boresight in free space.

Pattern Reconfigurable UHF RFID Reader Antenna Array.

The growing research interest in passive RFID (Radio Frequency Identification)-based devices and sensors in a diverse group of applications calls for flexibility in reader antenna performance. We propose a low-cost, easy-to-fabricate, and pattern reconfigurable UHF (Ultra High Frequency) RFID reader antenna in the RFID ISM band (902-928 MHz in the US). The antenna offers a 54 MHz bandwidth (890 - 944 MHz) and 8.9 dBi maximum gain. The proposed reconfigurable antenna can radiate four electronically switchable radiation beams in the azimuth plane. The antenna is LHCP (Left Hand Circularly Polarized) with axial ratio (AR) in the ranging from 0.45 dB to 7 dB in the RFID ISM band. Simulation and measurements are presented, and they are in good agreement. The proposed reader array performance is compared against a commercially available reader antenna. The pattern reconfigurable UHF RFID reader antenna not only increases the coverage area for conventional RFID applications but also opens the door to on-body RFID sensor implementation and indoor localization applications.

An Evaluation of Electromagnetic Exposure While Using Ultra-High Frequency Radiofrequency Identification (UHF RFID) Guns.

The aim is to evaluate specific absorption rate (SAR) values from exposure near handheld ultra-high frequency radiofrequency identification readers (UHF RFID guns—small electronic devices, or even portable computers with relevant accessories—emitting up to several watts of electromagnetic field (EMF) to search for RFID sensors (tags) attached to marked objects), in order to test the hypothesis that they have an insignificant environmental influence. Simulations of SAR in adult male and female models in seven exposure scenarios (gun near the head, arm, chest, hip/thigh of the operator searching for tags, or near to the chest and arm of the scanned person or a bystander). The results showed EMF exposure compliant with SAR limits for general public exposure (ICNIRP/European Recommendation 1999/519/EC) at emissions up to 1 W (reading range 3.5–11 m, depending on tag sensitivity). In the worst-case scenario, guns with a reading range exceeding 5 m (>2 W emission) may cause an SAR exceeding the general public limits in the palm of the user and the torso of the user, a bystander, or a scanned person; occupational exposure limits may be exceeded when emission >5 W. Users of electronic medical implants and pregnant women should be treated as individuals at particular risk in close proximity to guns, even at emissions of 1 W. Only UHF RFID guns emitting below 1 W may be considered as environmentally insignificant EMF sources.

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.

Fixed UHF RFID Reader Antenna Design for Practical Applications: A Guide for Antenna Engineers With Examples

An overview of Ultra High Frequency (UHF) Radio-Frequency Identification (RFID) practical applications and the reader antenna design requirements are presented in this paper. As each application is different and their physical, environmental, electrical, and Radio-Frequency (RF) requirements will also differ, a design methodology is proposed by analyzing all the requirements for a practical reader antenna. Reader antenna performance measures and test procedures are also formulated. As an example, an embeddable reader antenna is designed and fabricated for self-billing kiosk application in a retail environment. The designed antenna is measured in terms of various RF and RFID performance metrics and validated that it meets all the requirements sought by the application.

Meandered cross-shaped slot circularly polarised antenna for handheld UHF RFID reader

A compact meandered cross-shaped slot circularly polarized antenna for ultra high frequency (UHF) band radio frequency identification (RFID) reader applications is presented. Circularly polarized radiation is realized by introducing a slot on the diagonal axis of a square patch. Four different slot shapes are entrenched on one of the diagonal axes of the square patch for circularly polarized radiation and compared to the fixed overall volume of the antenna. The overall size of the antenna is reduced by increasing the perimeter of a slot within one quadrant of the patch. The meandered cross-shaped slot circularly polarized antenna is compact when compared with circular-, square- and cross-shaped slot circularly polarized antennas. Diagonally symmetric two- and four-meandered cross-shaped slot antennas are studied for further size miniaturization. Measured 3 dB axial ratio bandwidth of around 6 MHz with more than 2 dBic boresight gain and 10-dB reflection coefficient of 22 MHz is obtained with circularly polarized meandered cross-shaped four slot antenna. Size of the antenna is 0.189 λ0 × 0.189 λ0, where λ0 is the operating wavelength at 915 MHz.

Long read range Class‐3 UHF RFID system based on harmonic backscattering

A high sensitivity Class-3 ultra high-frequency (UHF) radio-frequency identification (RFID) system based on harmonic backscattering to achieve a long read-range is presented. Harmonic backscattering is a promising solution to solve the carrier leakage issue of UHF RFID reader to improve the sensitivity. In the proposed RFID system based on harmonic backscattering, the RFID reader transmits data with the fundamental frequency carrier and receives data with its second harmonic carrier, and the RFID tag employs a rectifier to generate both DC power and the second harmonic carrier for backscattering without impedance mismatch. The first harmonic Class-3 UHF RFID system based on National Instruments software defined radio platform is proposed and implemented. The proposed semi-passive harmonic RFID tag has dBm sensitivity. Test results show that the harmonic RFID system has a dBm sensitivity with the harmonic RFID tag whose signal-to-blocker ratio is dB at 20 m communication distance.

Printed UHF RFID Reader Antennas for Potential Retail Applications

Automation of retail industry is calling for the low cost solution due to its sheer size and varied needs. Printed electronics offers a great potential in addressing the needs in point-of-sales, inventory management and self-service, in particular the radio frequency identification (RFID) systems consisting of the printed components. Screen printed Ultra high frequency (UHF) RFID reader antennas have been investigated in this work for their application potentials in retails for achieving easy-implementation and low cost. The results obtained clearly demonstrated that the screen printed UHF RFID reader antennas are closely matching the performance of their circularly polarized patch antenna counterparts fabricated using the conventional chemical etching method in most critical specifications. The screen printed antennas have been explored for the monitoring of items on metal shelves targeting potential inventory management and point-of-sales applications. It has been found that all tagged items can be identified using a home developed UHF RFID system consisting of the printed antennas. The findings pave the way for the use of low cost printed antennas in the potential retail automation applications.

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.