Compact size flexible UHF RFID tag antenna for racing pigeon ring applications

A very small size radio frequency identification (RFID) tag antenna specifically designed for racing pigeon ring applications is proposed. The structure of this UHF tag is a closed‐loop type printed on a 30 × 8 mm² polyimide film of thickness 0.063 mm. Thus, it can be wrapped into a double layer plastic cylindrical ring of size similar to those used for racing pigeon. By simply tuning the inner width of the loop, good conjugate matching between the tag chip input impedance and the tag antenna can be achieved. When mounted onto a real preserved dried pigeon feet specimen, the measured impedance bandwidth of the tag antenna was 901‐929 MHz. Further experimental results have also shown that the proposed antenna has a maximum reading range of up to 50 cm.     

超高频RFID标签一致性的近场检测技术

超高频RFID标签一致性直接影响RFID系统中采集数据的识别率和准确率。采用接收信号强度指示RSSI(Received Signal Strength Indicator)技术及数理统计,采集标签反射信号强度,设定标准差阈值,作为标签一致性检测参数。研制弯折偶极子近场天线,实现0.1 mm近距离标签识读。利用屏蔽效应,在全自动卷筒式RFID标签套装上设置打点标识机构,对标签批量标记,可实现对柔性超高频RFID标签的高速、批量一致性检测。     

具有感应反馈环的超高频RFID标签天线设计

针对标签天线在RFID系统中的重要性,基于微带天线设计和电磁场散射理论,设计和分析了一种具有感应反馈环的超高频段RFID标签天线。天线的谐振频率为915 MHz,尺寸为78 mm×23 mm,天线显示近线性相位特性,在电压驻波比小于2的条件下,天线的阻抗带宽为100 MHz。可以通过调整感应反馈环的长度来调整天线的谐振频率,天线的增益为2.5 dBi左右。通过仿真和测量可知,这种天线能较好地满足RFID超高频段标签的要求。     

A low profile aperture coupled antenna with broadband circular polarization characteristics for UHF RFID applications

An aperture coupled microstrip‐line fed antenna (circular patch) with CP radiation is initially investigated. To achieve good CP radiation at 925 MHz UHF RFID frequency, the technique of loading an inverted C‐shaped slit into the circular patch is initially proposed. By further loading an open eccentric‐ring shaped parasitic element around the circular patch, an additional CP frequency can be excited at 910 MHz, and by combining these two CP frequencies, broad CP bandwidth that can cover the entire 902‐928 MHz UHF RFID band is achieved. Because of the parasitic element, the total dimension of proposed antenna is modified to 170 × 170 × 11.4 mm³. From the measured results, the impedance and CP bandwidths of the proposed antenna were 9.4% (859‐944 MHz) and 3.1% (902‐930 MHz). Furthermore, its corresponding peak gain and efficiency are 5.9 dBic and 84.3%, respectively. Further analyses have shown that the proposed antenna can also achieve good CP frequency agility across the desired UHF RFID operating band (902‐928 MHz).     

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.     

A dual band dual antenna with read range enhancement for UHF RFID tags

This article presents a novel dual antenna structure for dual ultra high frequency bands (f₁ = 866 MHz and f₂ = 915 MHz) for radio frequency identification tags. The proposed structure consists of two dual band antennas, one acting as a receiving antenna and the other as a backscattering antenna at both the frequency bands. The receiving antenna is designed to have input impedance complex conjugate to the impedance of tag IC in order to maximize power transfer between the antenna and the microchip. The backscattered antenna is designed to have real‐valued input impedance at both the operating frequency bands to obtain maximum differential radar cross section leading to read range enhancement. The dual band receiving antenna is designed by embedding a pair of thin slits at a radiating edge of inset fed microstrip antenna. The backscattering antenna is comprised of two elements, one is a comb‐shaped open ring element, and the other is a meander line structure which is within the open ring element. Compared to conventional antennas, the proposed dual antenna structure provides a read range enhancement due to improved maximum differential RCS. The proposed dual antenna produced 4.3 m and 6.8 m read range at 866 MHz and 915 MHz, respectively.     

Equilateral triangular patch antenna for UHF RFID applications

This article proposes an equilateral triangule‐shaped patch antenna for radio frequency identification (RFID) applications in the 900 MHz (902–928 MHz) ultra high frequency (UHF) band. To achieve optimal impedance matching and 10‐dB operating bandwidth at the desired band, the L‐shaped probe‐feed technique was used as the feeding structure of the proposed antenna. Furthermore, a near semicircular notch was also loaded into the patch so that good circularly polarized (CP) radiation can be generated from the proposed patch antenna. By simply shifting the position or radius of this notch, the CP frequency can be varied with ease. Here, 10‐dB impedance bandwidth and 3‐dB axial ratio bandwidth of 25 and 3% were achieved. Furthermore, stable gain variation of approximately 6 dBi was also exhibited across the RFID UHF band. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:580–586, 2014.     

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.     

Design of a compact size tag antenna based on split ring resonator for UHF RFID application

In this article, a new design of miniaturized split‐ring resonator antenna using a meander line technique with a simple impedance matching method applicable to UHF‐RFID tags is presented. The new approach is based on the integration of a meander line into the radiating element of SRR to reduce the electrical tag size and a theoretical demonstration to calculate the conjugate impedance matching and directly attach the antenna with the chip. The new SRR antenna, which is printed on the flexible substrate Arlon CuClad 250LX, is designed using Alien Higgs 3 RFID ASIC whose input impedance is 25‐j190. The prototype antenna has a low‐cost compact size (18.28 mm × 18.28 mm) with a read range higher than 4 m within the RFID UHF band and with a roughly 4.2‐m peak range at 915 MHz. As a proof of behavior, a tag prototype is fabricated and measured to operate at a UHF RFID band. Based on some works' results, an optimized design is obtained with a 48% size reduction compared with the classic split ring resonator antenna and with a good impedance matching the antenna with RFID ASIC without the need for any external matching network.     

Eccentric annular slot patch antenna with frequency agility for UHF RFID reader applications

The design of a simple ultrahigh frequency RFID (radio frequency identification) reader antenna that can operate within the North America RFID band (902–928 MHz) is studied. To generate circular polarization (CP) radiation in this band, a novel method of loading two narrow open‐ended slots (slits) into an eccentric annular slot patch is proposed. To allow optimum impedance matching with enhanced CP bandwidth, the radiating patch is loaded to an L‐shaped ground plane. From the experimental results, the proposed antenna can yield an impedance bandwidth (10‐dB return loss) between 650 MHz to 1125 MHz, while good CP bandwidth (3‐dB axial ratio, AR) from 901 MHz to 930 MHz is also attained. Furthermore, gain level and efficiency of more than 7.8 dBic and 90%, respectively, were also measured. By simply removing one of the slits, this proposed antenna can also be modified to operate within the China (840–846 MHz) and European (865–868 MHz) RFID band.     

Low‐profile UHF RFID reader antenna with CP radiation and coupled feeding technique

A low profile annular‐ring patch antenna with circularly polarized (CP) radiation for radio frequency identification (RFID) reader applications in the ultra‐high frequency (UHF) band (922‐928 MHz) is presented in this article. Perturbation method is applied by loading a pair of triangular open‐notch into the outer circumference of ring patch, and good impedance matching can be determined by using the coupled feeding technique. The overall size of this proposed antenna is 150 mm × 150 mm × 10.4 mm. The measured results show desirable 10‐dB impedance bandwidth and 3‐dB axial ratio (AR) bandwidth of 3.5% (908‐941 MHz) and 0.65% (922‐928 MHz), respectively. Stable antenna peak gain and efficiency of 7.2 dBic and 87% are also exhibited, respectively.     

Single‐fed broadband circularly polarized unidirectional antenna using folded plate with parasitic patch for universal UHF RFID readers

This research proposes a simple economical broadband circularly polarized antenna for universal ultra‐high frequency (UHF) RF identification (RFID) readers. The antenna utilizes a folded plate, a two‐corner truncated parasitic patch, and a ground plane. The folded plate, which is fabricated from one single plate, consists of a two‐corner truncated main patch, a wall patch, and a feed line, where the main patch is perpendicular to the wall patch, which is in turn perpendicular to the feed line. The folded plate enables currents to flow with a phase difference. The simulation results achieved an |S₁₁| < ?15 dB of 805–966 MHz (18% bandwidth), a 3‐dB axial ratio (AR) bandwidth of 834–962 MHz (14% AR bandwidth), and a gain higher than 8.6 dBic. The measured results obtained an |S₁₁| < ?15 dB of 806–970 MHz (18%), a 3‐dB AR bandwidth of 816–963 MHz (16%), and a gain greater than 7.8 dBic. The proposed antenna is applicable for universal UHF RFID readers as it covers the entire operating UHF RFID frequency range of 840–960 MHz. The parametric study and evolution of the proposed antenna are detailed in this research paper as well. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:575–587, 2016.     

无源UHF超高频标签天线设计与研究

无源UHF频段RFID技术信号传输速度快,覆盖距离远,通过与互联网、通讯等技术相结合,可实现全球范围内物品的跟踪与信息共享。该技术由射频模拟前端电路、控制逻辑电路等组成的无源UHF超高频射频识别标签系统,由外接天线与读写器完成通信,天线既要与识别标签相匹配,又要与读写器较好地通信,天线决定了标签是否能正常工作,同时也决定了信号传输的距离。为此,通过研究天线的匹配阻抗、形状尺寸与大小,以及频带的设计,探索出了低成本、高可靠的天线设计方案。     

Long read range and flexible UHF RFID tag antenna made of high conductivity graphene‐based film

An antenna made of a graphene‐based film with organic polyimide precursor of high conductivity 1.1 × 10⁶ S m^?1 and thickness 30 μm, operating in the ultrahigh frequency (UHF) band for radio frequency identification applications is presented in this article. The antenna is optimized to have a conjugate match to the impedance of the chip by tuning the design parameters. Tags are fabricated and tested using the designed antenna, which are shown to have realized gain above ?1.5 dBi and radiation efficiency beyond 90% in the whole UHF band from 860 to 960 MHz. The read range of proposed tag is greater than 12.3 m over the entire UHF band with a maximum value of 14 m at 920 MHz. In addition, the flexibility of the tags is demonstrated. After 2000 cycles of bending and stretching, the read range only decreases by 4.5 m comparing to the initial state at 915 MHz.     

一种UHF无源RFID标签芯片阻抗测试方法研究

提出一种用于UHF无源RFID标签芯片阻抗测试的新方法.利用ADS仿真软件对测试原理进行了仿真并实际制作了测试板.利用设计的测试板对NXP_XM芯片和Impinj_Monza4芯片进行了测试,分析了误差产生的原因,最终测试结果符合预期效果.     

Multifeed tri-band circularly polarized antenna for UHF/MW-RFID application

A compact three-port tri-band circularly polarized (CP) antenna for radio-frequency identification (RFID) technique is introduced. Four inverted-F radiating elements fed with a 90° phase delay feeding network realize the CP radiation at the FCC UHF-RFID band (0.902–0.928 GHz). With the slot-coupled feeding technique, Corner-truncated slot and patch have been employed to achieve CP radiation at MW-RFID bands (2.4–2.485/5.725–5.875 GHz). Decoupling structures are implemented to obtain excellent 20 dB port isolations during all operating bands. The relative impedance bandwidths in the three bands are 6.6%, 5.3%, and 5.1%, respectively, with peak gains of 2, 5.1, and 5.7 dBic.     

A circular patch antenna with parasitic element for UHF RFID applications

This article initially proposes a directly‐fed circular patch antenna with L‐shaped ground plane for Radio Frequency Identification (RFID) applications in the 900 MHz (902?928 MHz) ultrahigh frequency (UHF) band. To achieve circularly polarized (CP) radiation, two arc‐shaped notches are loaded into the main patch. To enhance the CP bandwidth so that the proposed antenna can also cover the UHF RFID band for Europe (866?869 MHz), a parasitic element is printed besides the main patch. Experimental measurements show that the 10‐dB return loss bandwidth of the proposed antenna was 30.95% (833?1138 MHz) and its corresponding 3‐dB axial ratio bandwidth was 8.95% (865?946 MHz). Good gain and radiation efficiency of more than 7 dBic and 90%, respectively, were also exhibited across the two desired UHF RFID bands. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:681–687, 2015.     

UHF RFID读写器零中频解调方式的研究与实现

在对UHF RFID读写器工作原理进行分析的基础上,介绍一种工作在UHF频段下的读写器的射频接口电路,并确定读写器的解调方式,重点对正交零中频解调方式进行研究,并给出读写器的实现方案.     

Balanced circularly polarized square loop antenna under even‐mode resonance

Design approach to a novel balanced, circularly polarized (CP) square loop antenna under even‐mode resonance is proposed in this paper. The loop antenna is diagonally fed by a fork‐like dipole launcher. By matching the respective natural boundary condition of the loop radiator and the dipole launcher, the resonant even‐mode with inherent CP radiation characteristic can be sufficiently excited. Both the bi‐ and uni‐directional cases are designed and investigated. A bi‐directional CP loop antenna with a 3‐dB ratio axial ratio (AR) bandwidth of 6.6% is designed at first. A uni‐directional antenna having a planar metallic reflector is further designed. The uni‐directional loop antenna exhibits excellent uni‐directional CP performance with a high front‐to‐back ratio of 40dB and a 3‐dB AR bandwidth of 7.6% in both theory and experiment.     

Wearable near‐field communication bracelet based on highly conductive graphene‐assembled films

Benefiting from the high conductivity and superb flexibility, graphene‐based materials are promising to replace metal for near‐field communication (NFC) applications. Herein, we report a flexible NFC tag antenna based on high‐conductivity graphene‐assembled films (HCGAFs) and investigate how the performance of the antenna is affected by antenna design and human body effect. The fabricated prototype via a one‐step laser‐direct mold engraving method shows a 10 dB bandwidth of 2.5 MHz centering at 13.70 MHz with a quality factor (Q) of 9.19. The maximum read range of the HCGAF NFC tag is measured to be around 7.5 cm, comparable to the commercially available metal NFC tags. Moreover, the flexible nature of HCGAFs guarantees excellent mechanical stability and deformation insensitivity, especially when compared to commercial metal‐based counterparts. We further demonstrate the practical applications of the HCGAF tag as key card and electronic business card in the vicinity of human body.