Compact meandered RFID tag antenna with high read range for UHF band applications

In this work, a compact, long read range, and an efficient spiral loop structure coupled tag antenna is proposed for UHF‐RFID applications. Meandered line element is inductively coupled to spiral loop for matching its input impedance to Higgs‐4 chip. Equivalent circuit of antenna is extracted to analyze its working mechanism in the operating band. Experimental characterization validates the performance of proposed tag antenna in free space and on cardboard sheet in terms of read range, tag sensitivity, and differential radar cross section with an EIRP of 3.28 W. The measured radiation pattern of the tag is found to be omnidirectional in H plane and figure of eight in E plane. The tag's read range is measured on objects like fiber, wood, plastic, and glass in outdoor scenario to study its environment tolerance. The tag antenna has volumetric size of 1736 mm³ and read range of 13.6 m in US RFID band.     

Linearly tapered meander line cross dipole circularly polarized antenna for UHF RFID tag applications

In this article, a circularly polarized antenna for ultra‐high frequency radio frequency identification (RFID) tag is presented. The circular polarization is realized by two orthogonal, unequal length linearly tapered meander line cross dipoles. The meander structure with capacitive tip loading is used for size miniaturization of the antenna. A modified T‐match network is employed to feed the cross dipole structure. The measured 10‐dB return loss bandwidth of the cross dipole antenna is 17 MHz (908‐923 MHz) and the corresponding 3‐dB axial ratio bandwidth is 6 MHz (912‐918 MHz). The overall size of the proposed antenna is 0.17λ₀ × 0.17λ₀ at 915 MHz. The maximum read range between the reader and the tag with the proposed antenna is 4.7 m larger than the analogous linearly polarized tag antenna due to the reduction in polarization loss between the tag and reader antennas. Thus, a maximum read range of 15.66 m with the gain of 1.28 dBic is achieved at 915 MHz.     

RFID tag antenna for ultra and super high frequency band applications

A novel dual‐band antenna for radio frequency identification tag is proposed for ultra high frequency (UHF: 915 MHz) and super high frequency (SHF: 2450 MHz) bands. The proposed tag antenna is a single sided dual‐antenna structure, designed on the grounded (metallic) dielectric substrate. The proposed tag antenna can be used on any kind of surfaces including metals without severe performance degradation due to its metallic ground plane. At UHF band, proposed tag antenna works as dual‐antenna structure. In the dual‐antenna structure, one antenna works for receiving and another for backscattering. Due to separate backscatterer, the maximum differential radar cross section improved and results in the enhancement of the maximum read range. Whereas at SHF band, proposed antenna works as conventional single antenna structure and during operations it switches between receiving and backscattering modes. The proposed antenna consists of a meandered line antenna and a rectangular patch antenna loaded with an F‐shaped and an inverted L‐shaped slots. The S‐parameters are measured by means of differential probe technique. Simulated and measured results are observed in good agreement. The read range is observed about 5 and 6 m at 915 and 2450 MHz, respectively. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:640–650, 2016.     

A single sided dual‐antenna structure for UHF RFID tag applications

In this article, a dual‐antenna structure is presented for UHF RFID tag. The proposed structure is made of two L‐shaped strip antennas along with a cross‐shaped slot loaded patch. One antenna is exclusively used for receiving and harvesting full energy with complex conjugate of tag chip, whereas another used as backscatter to enhance maximum differential radar cross section with purely real input impedance, which results in the enhancement of read range. Further, electromagnetic band gap structure is used around the dual‐antenna structure to increase the gain which results in improved read range. The proposed antennas are fabricated and the S‐parameters are measured with the help of differential probe technique. Simulation and measurement results are found in good agreement. The performance of the proposed antenna is also investigated when it placed on different materials such as metal, wood, glass, and plastic. The study shows that the read range of antenna increases considerably when it is mounted on a metallic surface, while the maximum performance is observed when the antenna is attached on a glass surface with highest relative permittivity. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:619–628, 2015.     

Novel electrically small meander line RFID tag antenna

This article introduces a new RFID tag antenna designed for operation at 915 MHz. The proposed antenna is electrically small with dimensions (λ₀/15) × (λ₀/15). It features two vivaldi‐like apertures flipped with respect to each other around an axis parallel to their slotted edges. Each aperture is loaded with a meander line with multiple loops. The two sides of the proposed antenna are fed via a common slot line that is coupled electromagnetically to a perpendicular microstrip line at the other side of a dielectric substrate. The new antenna are fabricated using printed circuit board technology and the fabricated prototype is experimentally characterized. The optimization and theoretical investigation of the proposed antenna are performed via both HFSS and CST. The two simulators agree very well with each other and with measurements. The characteristics of the new RFID antenna are generally good, such as: small size (22 mm²), low profile (0.8 mm), flexible impedance matching, reasonable impedance bandwidth (8%), omni‐directional radiation, low cross‐polarization level (?20 dB at broadside), acceptable radiation efficiency (76%), and gain (?0.3 dBi). © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 23: 639–645, 2013.     

Platform tolerant dual‐band UHF‐RFID tag antenna with enhanced read range using artificial magnetic conductor structures

In this work, a platform tolerant novel dual band tag antenna is proposed for UHF‐RFID bands used in Europe (855‐867 MHz ) and Japan (950‐955 MHz). Asymmetrical shunt stub feed network is employed to effectively match its impedance to the microchip (Alien Higgs‐4). The antenna miniaturization is achieved by embedding inverted L‐shaped slit on left side of the patch. Also, asymmetrical stepped rectangular slot is embedded to further achieve the optimized dual band response at the desired resonant frequencies (f₁ = 866 MHz and f₂ = 953 MHz). To further enhance its radiation performance on conductive objects like metallic surfaces, the proposed tag is integrated with artificial magnetic conductor (AMC) structure. Also, antenna parameters such as main lobe gain, directivity, front‐to‐back ratio parameters are examined for the integrated tag in free space and on metallic sheet. The proposed integrated tag exhibits directional radiation pattern making it insensitive to underlying object and thus platform tolerant. Further, the proposed integrated tag exhibits steady gain response inside the resonating bands on different sized metallic sheets. The proposed integrated tag is compact (2635 mm³) covering European band with a read range of 7.3 m and Japanese band with a read range of 10.8 m.     

Development of a novel radio frequency identification chipless tag with multifrequency response

This article presents an innovative contribution, which is the design of a novel radio frequency identification chipless tag characterized by a reduced size and a multifrequency response. It consists of a microstrip grounded structure based on a circular patch coupled with meandered metal strip. The adopted approach is an encoding frequency approach that ensures a capacity of 20 data bits in the ultra wideband. The main aim of this contribution is to introduce a novel configuration resulting from the study of the classic principles of the chipless tag design. It focuses on the design of an encoding surface associated with the same shape having the role of the transmitter/receiver antenna in order to mainly gain time to work on another tag component. The tag is analyzed, optimized, and measured to validate its feasibility and to prove the possibility of its commercial application.     

新型无源UHF RFID双端口标签设计

针对无源UHF RFID系统通信距离受限的问题,提出了一种新型无源双端口智能标签的设计方案.阐述了智能选择的实现方法以及提高系统识别距离的原理,并给出了标签其他部分电路包括整流及稳压电路、调制电路和解调电路的电路结构,电路基于0.18 μm CMOS工艺实现.仿真结果表明:各部分电路均可实现正常功能.     

A compact proximity‐fed 2.4 GHz monostatic antenna with wide‐band SIC characteristics for in‐band full duplex applications

This article presents a dual polarized, proximity‐fed monostatic patch antenna (single radiator for both transmit and receive modes) with improved interport isolation for 2.4 GHz in‐band full duplex (IBFD) applications. The proximity‐fed radiating patch offers comparatively wider impedance bandwidth for presented design. Very nice self‐interference cancelation (SIC) levels for intended impedance bandwidth have been achieved through differential receive (R_x) mode configuration. The differential R_x mode based on 180° ring hybrid coupler acts as a signal inversion mechanism for effective suppression or cancelation of in‐band self‐interference (SI) that is, the leakage from transmit port. The implemented prototype of proposed antenna achieves ≥87 dB peak isolation for dual polarized IBFD operation. Moreover, the recorded interport isolation for validation model ≥60 dB within 10 dB‐return loss bandwidth of 90 MHz (2.36‐2.45 GHz). The measured radiation characteristics of implemented antenna demonstrate nice gain and low cross‐polarization levels for both transmit (T_x) and receive (R_x) modes. The dimensions of implemented antenna are 70 × 75 × 4.8 mm³. The novelty of this work is wide‐band SIC performance for monostatic antenna configuration with compact structure of presented design.