Radio-frequency identification (RFID) is being widely used in supply chain and logistics applications for wireless identification and the tracking and tracing of goods, with excellent performance for the long-range interrogation of tagged pallets and cases (up to 4-6 m, with passive tags). Item-level tagging (ILT) has also received much attention, especially in the pharmaceutical and retail industries. Low-frequency (125-134 KHz) and high-frequency (HF) (13.56 MHz) RFID systems have traditionally been used for ILT applications, where the radio-frequency (RF) power from the reader is delivered to the passive tags by inductive coupling. Recently, ultra-HF (UHF) (840-960 MHz) near-field (NF) RFID systems [1] have attracted increasing attention because of the merits of the much higher reading speed and capability to detect a larger number of tags (bulk reading). A UHF NF RFID system is a valuable solution to implement a reliable short-range wireless link (up to a few tens of centimeters) for ILT applications. Because the tags can be made smaller, RFID-based applications can be extended to extremely minuscule items (e.g., retail apparel, jewelry, drugs, rented apparel) as well as the successful implementation of RFID-based storage spaces, smart conveyor belts, and shopping carts.

/pdf/considering-high-performance-near-field-reader-antennas-1mymt6plp9.pdf

Considering High-Performance Near-Field Reader Antennas: Comparisons of Proposed Antenna Layouts for Ultrahigh-Frequency Near-Field Radio-Frequency Identification

An array of 2 × 2 travelling wave antennas (TWAs) is proposed for near-field RFID applications in the UHF band (865-928 MHz). Each array element is characterised by a meandered line based on coplanar waveguide technology. All the TWAs end on a matched load, which allows for non-stationary current and field distributions as well as a low far-field gain. Thus, strong and uniform fields within a confined volume above the antenna surface have been obtained, with a field maximisation in the antenna central area, where tagged items are supposed to lie on. The meander geometry allows exciting all-field components, making the tag detection almost independent of tag location and orientation when it lies on the antenna surface. Since TWAs are not resonating structures, the proposed antenna results are scalable, allowing for an easy integration in commercial readers with arbitrary sizes. In particular, a 275 × 135 × 10 mm
 3 
antenna has been designed to fit a particular commercial desktop reader size. Measured tests on the antenna read range were carried out, showing a field distribution maximised in the broadside direction within 10 cm from the antenna surface.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/el.2013.3099

Meandered TWAs array for near‐field UHF RFID applications

인체 near field magnetic communication을 위한 전력전달 특성에 관한 연구

A broadband center-fed ultra-high frequency (UHF) near-field radio frequency identification (RFID) reader antenna is proposed and investigated in this letter. The design utilizes four tapered double-side parallel stripline (TDSPSL)-fed dipoles to form a circular loop to achieve broadband impedance matching and strong and uniform magnetic field distribution. Parametric studies are carried out to characterize the design concept. The proposed antenna was fabricated and measured. The measured 10-dB impedance bandwidth is 236 MHz (814–1050 MHz), which covers the entire UHF RFID frequency band. The maximum reading distance is 210 mm at 30 dBm input power. Moreover the antenna can achieve a 100% read percentage within the height of 135 mm for multitag detection. The measured results agree well with the simulated ones.

Novel Broadband Center-Fed UHF Near-Field RFID Reader Antenna

Automatic goods inventory on the shelf is an important Ultra High Frequency (UHF) Radio Frequency Identification (RFID) application. Compared to other applications, it has some unique requirements: 1) Confined read region to avoid the cross reads to other tiers and shelves; 2) Positioning capability to know where along the shelf the tag is; 3) Low total system cost to support many shelves in the application. In this paper, an innovative UHF RFID solution is proposed for the RFID shelf. It contains two key technologies. First, the proposed near field (NF) shelf antenna in [1] is improved to provide the possibility to connect 5 cascaded antennas to one antenna port. It can save the system cost by reducing the number of needed readers. Second, a phase difference measurement based tag positioning method is proposed. To support different applications, it can provide both tier level and item level positioning for the goods on the shelf. Based on the measurement results, the proposed method can get the item level positioning accuracy with an average error of 4.16cm. It can also get 100% tier level positioning accuracy.

UHF RFID shelf solution with cascaded reader antenna and positioning capability

A novel broadband antenna for ultrahigh-frequency (UHF) near-field radio frequency identification (RFID) applications is presented. The antenna is composed of a grounded coplanar waveguide (GCPW), a coplanar stripline (CPS), a lumped balun, multiple resistors, and a finite-sized ground plane. The load impedance is equal to the characteristic impedance of the CPS, hence traveling wave can transmit along the CPS. The proposed antenna structure can produce large currents along the CPS so that a strong and uniform magnetic field distribution is excited in the adjacent region around the antenna. The antenna geometry, design concept, simulated, and measured results are carefully discussed throughout the paper. Measurements show that the antenna operating with a commercial reader demonstrates good performance of tag identification with inductive coupling for near-field RFID applications. In addition, the parametric study is conducted to facilitate the design and optimization processes for engineers.

Yao Gao

Papers

A Robust UHF Near-Field RFID Reader Antenna