A Miniaturized Circularly Polarized Antenna Design for RFID Reader

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.

In this paper, the simulation of radiation pattern of the proposed RFID C-slot tag antenna on a coated metallic cylindrical surface is presented. It is found that the radiation pattern in the shadow zone (behind the product) from the proposed RFID tag is stronger than that from the electric current source case (electric tag). Thus, the proposed C-slot tag antenna is useful for the RFID application especially for the curved metallic surface product.

This paper presents the design of ultra-high frequency (UHF) radio frequency identification (RFID) reader antenna using low dielectric constant of microwave substrate. An RFID reader antenna emits electromagnetic signals to the microchip in the tag, and the microchip will be energized by modulating the wave and returns to the reader antenna. The process of wave emitting is known as backscattering due to the presence of tag been detected by the reader. High-dielectric constant substrate, for example flame-retardant-4 (FR4) which is commonly used for microstrip patch antenna, is high in dielectric constant and dielectric loss. Thus, this will lead to low gain and directivity properties of the antenna. To overcome this matter, low-dielectric constant substrate which is Taconic TLY-5 was proposed to be utilized for microstrip patch antenna design. The TLY-5 microstrip substrate thickness used is 1.6 mm, dielectric constant of 2.2, and loss tangent of 0.019. A high-conductivity metal which is typically a conductive copper is been used for the two layers of dielectric substrate, the top radiating patch layer and bottom ground layer where the copper thickness is 0.035 mm. Microstrip feed line is used for this UHF RFID reader antenna. The width of the feed line was tuned to obtain impedance matching of 50 Ω. The proposed antenna which is fork-shaped patch antenna was simulated using Computer Simulation Technology (CST) and Microwave Studio software at resonant frequency of 910 MHz with the outcome results of 7.985 dB gain and −11.11 dB return loss. Nevertheless, the typical value obtained for VSWR is less than 2.

Passive UHF (ultra high frequency) RFID (radio frequency identification) is a promising technology for products tracking in logistics or routing packages in supply chain. However, passive UHF RFID tag suffers a lot when it is placed on conductive plane or water surface. Many designs like microstrip antenna and ferrite antenna have been used to solve this metal-water problem. But their use is limited by narrow bandwidth and low antenna gain. The electromagnetic band gap (EBG) material which exhibits a unique forbidden band gap at certain frequency offers a potential solution to solve the problem of backside objects effects. Previous research paper indicated that the dipole RFID antenna above three-layer mushroom like EBG material exhibited a good antenna gain and long read range. However, the complicated structure and high material cost greatly limit the application of tag. In this paper, we developed a new type of EBG material which uses ferrite film to reduce size and lower forbidden frequency. A commercial ferrite film which has a high permeability is applied to form two-layer mushroom like EBG material for UHF RFID. This two-layer mushroom like EBG material is a two-layer structure with a ground plane. The design of EBG material for UHF RFID which operates at 915 MHz was discussed in this paper. An EBG tag on metal with a gain of 7 dBi was achieved in simulation. The simulation results showed that the RFID tag still could be read on EBG substrate with a good gain (~7 dBi).

Oilfield tubulars (typically metallic pipes) and other types of oilfield equipment are typically stored in outdoor areas and may be scattered around the field. Managing these types of inventory is challenging and costly, as it requires significant labor resources. Therefore, inventory inaccuracy is common, and data-driven decisions may not be possible in a timely manner. We propose the use of radio frequency identification (RFID) for tracking oilfield tubulars and similar, outdoor-stored, equipment. Our proposed application utilizes passive ultra-high frequency (UHF) RFID technology that enables capturing unique serial identification numbers that are attached to inventory items from a distance of several meters. Passive UHF RFID tags require no batteries to operate. Typical tag cost is low. Each tag is placed on an inventory item and corresponds to a database entry containing specific information about this item. The tag communicates its serial number using power provided by an RFID reader radio transmission. The RFID reader is securely mounted to the underside of a UAV flown over the field. Captured RFID tags are either stored locally and retrieved once the UAV lands, or are wirelessly transmitted to a constantly updating inventory database. In addition to tag ID, the captured data typically includes time and date stamp, as well as location data. This research project included the design and manufacturing of an enclosure to house a RFID reader system which includes a host computer, embedded reader, antenna, power source, and necessary components for user interface. Specialized mounts were designed and manufactured to attach the enclosure and antenna to the UAV. The project incorporated the development of "middleware", specialized software installed on the host computer to communicate with the reader. The reader handles low-level communication with the antenna. To reduce network traffic, event management and data filtering are efficiently performed. The results of several UAV flights in experimental areas are presented and discussed. Various brands of passive RFID tags for oilfield applications were tested. Particular attention was given to population density of the items, stacking configuration, vertical altitude distance between reader and tags, and time to collect inventory data for a given area of surveillance. As RFID applications are increasing in the oil, gas, solar, and other sectors of the energy production industries, UAVs can effectively be used to get important operational and inventory data. UAV use is particularly appealing in inaccessible and remote locations.

This paper presents a wideband and high gain circularly polarized ultra-high-frequency (UHF) radio frequency identification (RFID) reader antenna. Such antenna is composed of one main radiation patch and one parasitic radiation patch with air as the dielectric layer. And two feeding lines connect to the main radiation patch with 90 deg phase difference. Numerical optimizations and experimental demonstrations are performed to investigate the performances of the proposed antenna and good agreements are achieved. This antenna can cover the whole UHF RFID frequency band (840–960 MHz) with gain of 9.7 dBi, which is suitable for universal UHF RFID applications.

A new circularly polarized (CP) slot antenna with a small gap and a stick-shaped shorted strip is presented. The proposed antenna has a sufficient bandwidth for ultrahigh frequency (UHF) radio-frequency identification (RFID) reader applications. The antenna structure consists of a rectangular slot with a small gap, a stick-shaped shorted strip and a 50 Ω coplanar waveguide (CPW) feedline with an asymmetrical ground plane. By using the stick -shaped shorted strip to disturb magnetic current distribution on the slot, the CP radiation can be generated. The measured results demonstrate that the proposed antenna can reach a 10 dB return loss impedance bandwidth of 14.1 % (894–1030 MHz) and a 3 dB axial ratio (AR) bandwidth of 6.4 % (910–970 MHz). The whole antenna size is 80 × 80 × 1.6 mm3.

This paper presents a 2-D localization system based on phase-of-arrival evaluation of passive ultrahigh frequency (UHF) radio frequency identification (RFID) transponders. To handle the ambiguity caused by phase evaluation, several tags are arranged to form a uniform linear array. A multiple input multiple output system, where sequentially each frontend is configured to work as 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, one commercial off-the-shelf RFID reader, several transceiver frontends, baseband hardware, and signal processing. Measurements were carried out in an indoor office environment, where the $3.5~{\rm m} \times 2.5$ m measurement zone was surrounded by drywalls and concrete floor and ceiling, and the experimental results showed robust and accurate localization with a root-mean-square deviation of 0.011 m and a maximum error of 0.032 m. These experimental results were confirmed by simulations, which were performed to determine the limits of the system accuracy.

This paper describes the development of four different ultra-high frequency (UHF) radio frequency identification (RFID) tag antenna using polycarbonate material or transparent paper as the substrate and aluminum tape as the radiating element. The main advantage of the method is that the materials are easy to obtain where it can be found in any hardware stores or in any general online shop. Plus, the antennas are designed in such a way that a meander line is traced along the shape of a bowtie antenna so that the antenna would operate at UHF band. The results of all four of the tag antenna designs are discussed and compared using graph obtained from Computer Simulation Technology (CST) simulation results and measurement results obtained from a portable Vector Network Analyzer (VNA) for the reflection coefficient, S 11 , and measurement results taken from VNA in chamber room for the radiation pattern. Finally, the results show that the measured results are in agreement with the simulated result and that the UHF RFID tag antennas are able to operate at UHF RFID band.

This paper presents a circularly polarized ultrahigh frequency (UHF) antenna for radio frequency identification (RFID) readers. The proposed antenna is a cross-dipole configuration consisting of two dipole pairs printed on the top and bottom of the substrate. Each dipole pair is made up of arrow-shaped elements that are arranged diagonally and are linked by delay lines to produce circular polarization. An artificial magnetic conductor (AMC) is placed at a distance of /15 below the antenna to improve its performance, where λ is the free space wavelength at 900 MHz. The AMC-backed antenna has an impedance bandwidth of 850-950 MHz and an axial ratio bandwidth of 890-910 MHz. The peak gain of the antenna increases from -1.31 dB (without AMC) to 4.6 dB (with AMC) at 900 MHz.

The paper outline development and simulation of Pulse Interval Encoding (PIE) encoder architecture for Ultra High Frequency (UHF) Radio Frequency Identification (RFID) reader based on Field Programmable Gate Array (FPGA). The PIE encoder architecture presented in this paper is according to International Organization for Standardization and International Electrotechnical Commission (ISO/IEC 18000-6) protocol. The behavior of the PIE encoder architecture is realized by derivation of Verilog Hardware Description Language (HDL) code in Quartus II software. Utilizing the ModelSim-Altera, the PIE encoder architecture is simulated to observe its functionality. The designing of the encoder is intended for uses in UHF RFID passive interrogator.

Passive UHF (Ultra High Frequency) RFID (Radio Frequency Identification) is a promising technology for products tracking in logistics or routing packages in supply chain. Usually, the UHF RFID antenna is made by etched copper, or aluminum. These etching process introduce chemical wastes during the etching process. Recently, printing silver paste becomes popular due to its environmental friendly manufacturing process. However, there are two drawbacks on printed silver paste RFID antenna. One is low conductivity compared to metal and the other is the high material cost. In this paper, we exam the effects of printing thickness on the performance of UHF RFID tags and summarize the optimized thickness for different read range requirements. A commercial conductive silver paste is printed on PET film as RFID tag antennas. Both finite element simulations and experiments are conducted to evaluate the effects of printed thickness. The simulation results presents that the 10 um thick RFID antenna exhibits relatively good radiation efficiency. The results indicate that 10 um thick RFID tag antenna presents the minimum turn-on power of 18 dBm to 22 dBm which is enough for most applications. The simulation and measurement results present that thinner printed silver paste RFID tag antenna is a potential solution for low cost UHF RFID tags. The cost of these tags could be lower than current etched Al/Cu RFID tags because of material saving.

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.

We developed hardware and software to perform exposure studies of the effects of certain radio frequency (RF) electromagnetic fields on solid and liquid pharmaceuticals and biologies. The RF fields generated by our systems are similar to those emitted by radio frequency identification (RFID) readers operating in the USA licensed high frequency (HF) and ultra high frequency (UHF) bands (13.56 and 915 MHz respectively). Our systems can expose drug samples (pharmaceuticals and biologies) to uniform electric (E) and/or magnetic (H) fields at levels that are much higher than those experienced by drugs near "worst-case" readers at a distance of 20 cm. Worst-case readers are defined as those that emit the highest allowable field strengths. Maximum field strengths near these readers were identified by measurements and computations of fields from commercial readers, and are extrapolated to the maximum allowable effective isotropic radiated power or field strength dictated by the U.S. Federal Communications Commission (FCC). The UHF system we developed included a commercially available circularly polarized antenna, a microwave generator with pulse modulation, a high power amplifier, a plastic foam enclosure, and fiber optic temperature monitoring probes placed in the drugs and the surrounding air. The HF system we developed included a specially designed Helmholtz coil pair, an HF signal generator with pulse modulation, an HF amplifier, an RF impedance matching device, and the same enclosure, and thermometry system as in the UHF system. Exposures can be performed for each drug in both its retail primary package (the smallest container produced with an RFID tag on it, e.g. bottle) and in 54 mm diameter culture dishes. The containers are suitable for exposing a wide variety of formulations of drugs (tablets, liquids, powers, capsules, creams, etc.). Exposures of drugs in culture dishes assure uniform induced electric fields and currents. In contrast, exposures in the primary containers (e.g. vials) allow studies that account for the interactions of RF fields with the packaging materials and container geometry. In our UHF system we can expose drugs to over 20 watts effective isotropic radiated power over 5 times the FCC limits. We evaluated H fields emitted by commercially available RFID readers. In our HF system we can expose drugs to at least 5 times the H field they produce at 20 cm from the reader. We can expose samples to 5 A/m in primary packaging or in special organ culture dishes with an outer concentric ring. The ring has inner and outer diameters of 32 mm and 55 mm respectively. Computer monitoring of power, drug temperature, and air temperature can be performed continuously during exposure. Surrounding air temperature is monitored at all times while in our lab (storage and exposure) and while shipped to drug laboratories for analysis.

In this paper, the use of hollow metal heating, ventilating, and air-conditioning (HVAC) ducts as a potential communication channel between passive ultrahigh-frequency (UHF) radio-frequency identification (RFID) readers and tags is studied. HVAC ducts behave as electromagnetic waveguides with much lower signal attenuation compared to free-space propagation. This low-loss electromagnetic environment allows one to greatly increase the communication range of passive UHF RFID systems and build, for example, a long range passive sensor network spanning an entire infrastructure such as a large building. In this work, it is shown both theoretically and experimentally that the read range of passive UHF RFID systems can be increased by multiple times compared to operation in a free-space environment.