Analysis and characterization of transponder antennae for radio frequency identification (RFID) systems

An investigation into the use of various radio frequency identification (RFID) antenna designs was performed. Passive RFID tag antennae with a resonant frequency range of 902–928 MHz were tested for robustness and efficiency in the Packaging Science RFID Laboratory at the University of Florida. Commercially available single‐ and dual‐dipole tags were examined for read performance. Electromagnetic modelling software was used to model the impedance matching and detuning effects of nearby conducting surfaces. s‐Parameters, current densities and polar plots of various dipole designs were estimated. Strategies used to shorten antenna length, such as capacitive loading, were evaluated. A simple half‐wave dipole antenna was modelled in order to determine the effect of length on resonant frequency and performance. Parameter sweeps showed that a length of 14.4 cm was required for resonance at 915 MHz and 50 Ω termination. Capacitive loads shortened the dipole to 8.4 cm while adding 4.2 cm to height. It was verified that a conducting surface, such as metal packaging, had strong detuning effects on RFID tag antennae. Different methods, such as tuning stubs, alleviated the detuning effects by allowing bandwidths twice as large as with a simple dipole. Finally, the rationale for commercially available RFID antenna designs was discussed. It was found that analysis of actual antenna tag structures in the laboratory and exploring different methods to improve efficiency can lead to improvements in RFID performance. Copyright © 2005 John Wiley & Sons, Ltd.     

Readability and Modulated Signal Strength of Two Different Ultra‐high Frequency Radio Frequency Identification Tags on Different Packaging

Radio frequency identification (RFID) does not require the line‐of‐sight scanning, which is a benefit in comparison with barcodes; moreover, it is believed that it improves the inventory management. Nowadays, this is still a costly solution; however, in the near future, it is expected to become widespread especially in packaging. This paper analyses some effects that have to be considered before the application of the system on packaging. The readability of two ultra‐high frequency RFID tags with different antenna sizes and shapes but the same reading range as stated by the supplier was evaluated. The influence of water and metal was analysed by labelling each tag onto an empty corrugated box, a box filled with water and a box covered with aluminium foil on the inside. The read rate in a line‐of‐sight and the readability in a horizontal plane were measured, applying a horizontal linearly polarized wave. The strength of the signal in a direct line‐of‐sight between the reader antenna, and RFID tag was measured with circularly polarized waves. The obtained results confirmed the effects of the tagged antenna and of the labelled boxes content. To show the effect clearly, the influence of metal and water on the two‐dimensional horizontal tag readability was measured and presented with two‐dimensional sketches of tag reading/non‐reading zones. Different results were obtained for both tags, with the content of labelled boxes having a great influence. Copyright © 2011 John Wiley & Sons, Ltd.     

多应用环境下超高频RFID标签天线设计

 金属等环境介质对射频信号的干扰影响着无源UHF RFID系统性能在应用中的充分发挥.利用三维结构的微带天线模型将贴片天线在电气上与金属表面分离以构成与底面无关的RFID标签,但因此而加大了RFID标签结构的复杂性,造成RFID标签生产成本的增加.通过改变微带天线的馈电形式,将传统非平衡单馈电结构的微带天线改进成平衡双馈电结构,三维的微带天线也简化成平板结构,减小了RFID标签体积.该天线模型不但可以降低RFID标签制造工艺难度,也为RFID标签在不同应用环境中提供了兼容性.     

RFID丝印墨层厚度影响因素的研究

介绍了丝网印刷RFID标签天线的工艺特点;在分析了标签天线电阻的计算方法的基础上,提出了天线电阻主要受天线墨层厚度和导电油墨导电性能两方面的影响。分别分析了丝网、刮墨刀、丝网目数等因素对天线墨层厚度的影响,以及导电油墨的黏度及导电油墨的干燥效果对其导电性能的影响。为实际生产中,调整丝印RFID天线的电阻提供理论参考。     

The effects of item composition,tag inlay design,reader antenna polarization,power and transponder orientation on the dynamic coupling efficiency of backscatter ultra‐high frequency radio frequency identification

The effects of packaged content, packaging material, transponder inlay design, reader antenna polarization, interrogation power and transponder orientation on the detection rate of ultra‐high frequency radio frequency identification (UHF RFID) passive transponders were studied. The influence of individual factors and their interactions were determined using general linear model analysis of variance. Influences originated in order of importance, from sample type, antenna polarization, power and inlay design. Important interactions in decreasing order of significance exist between: power and antenna polarization; sample type and antenna polarization; sample type and inlay design; inlay design and antenna polarization; sample type, power and antenna polarization; sample type and power; inlay design and power; sample type, inlay design and power. It was also observed that random orientation of tags did not cause a statistically significant variation in tag detection rate. It can be concluded that the use of UHF RFID for item level of food requires multi‐parameter assessment before hand. Copyright © 2009 John Wiley & Sons, Ltd.     

Mobile RFID Tag Detection Influence Factors and Prediction of Tag Detectability

Radio-frequency identification (RFID) readers are powered RF devices that communicate with tags (whether mobile or fixed) and read necessary information to be processed. A mobile RFID tag is detected by an RFID antenna. In a mobile RFID where the RFID tag is attached to a mobile object such as a vehicle, a human, or an animal, information is more difficult to detect than in the case where the tag is attached to a stationary object. Currently, deployment engineers and researchers use trial-and-error approaches to decide on the best conditions of the tag detection influence factors which affect tag detectability (detection rate). As expected, these approaches are time consuming. Even though mobile RFID systems have become widely used in industry and tag detection problems are crucial at deployment, very few researches on them have been conducted so far. Thus, a quick and simple method for finding tag detectability is needed to improve the traditional time consuming trial-and-error method. In this paper, we propose a unique approach ldquothe intelligent prediction method of tag detection rate using support vector machine (SVM).rdquo The intelligent method predicts the mobile RFID tag detectability instead of the trial-and-error experimental procedures. The simulation results of the proposed method are very comparable to the trial-and-error experimental approach. The proposed intelligent method gives a very high accuracy of mobile RFID tag detectability prediction and proves to be superior to the current method in time as well cost savings. The predicted tag detectability results can be used for analyzing mobile RFID tag detection influence factors and their conditions.     

A New Wireless Sensor System for Smart Diapers

This letter presents a new wireless sensor system for smart diaper application, which consists of an interrogator circuit, an antenna, and a passive LC resonating sensor tag. The wireless link between the interrogator circuit and the sensor tag is established through the inductive coupling. The wetting of the diaper shifts the resonating frequency of the sensor tag, changing the inductive link, and thus trigger an ldquoonrdquo or ldquooffrdquo condition reflected at the interrogator circuit. With suitable sensor tags, smart diapers can be achieved in a straightforward and low cost approach.     

基于低频触发的高精度RFID定位系统的设计与实现

为了解决传统RFID定位技术中存在的定位精度差和电子标签功耗高这2个问题,提出了一种基于低频触发的2.4GHz高精度区域定位系统的设计方案。该方案将低频125kHz触发信号与2.4GHz射频信号相结合,采用低频唤醒的方法极大降低了电子标签的功耗,利用可调节触发距离的触发机制将RFID系统的定位精度进一步提高.基于该方案设计了2.4GHz有源电子标签、125kHz触发器和2.4GHz阅读器三个子系统。阅读器与触发器的分离式设计,节约了铺设成本。系统硬件电路设计中加入了可调电位器和数字电压调节器,分别对识别距离和触发距离进行调节,使设备的配置更为方便,增强了系统的实用性。测试数据显示,阅读器与标签的最大通信距离长达120m,有源电子标签的待机时间约为2a(年),RFID定位系统能够实现1~5.2m的可调定位精度。测试结果验证了该方案的有效性。     

Tag identification enhancement by using a distributed antenna structure for radio frequency identification systems

This study presents a distributed antenna structure operating at a frequency of 915 MHz to increase the tag identification sensitivity for passive radio frequency identification (RFID) systems. The distributed antennas are connected to a reader with a four-port power splitter/combiner which consists of Wilkinson power splitters (WPSs), band pass filters (BPFs) and power amplifiers (PAs). Due to the polarisation of the electromagnetic field, the antennas are positioned on opposite sides in both vertical and horizontal directions of the object. This positioning improves the performance of the system, and increases the sensitivity when identifying unclearly positioned tags. An experimental RFID system is also set up to demonstrate the proposed structure. Simulation and experimental results indicate that using four distributed patch antennae can improve tag identification in passive RFID systems.     

RFID天线的丝印工艺研究

为分析优化RFID天线的丝网印刷过程并提高其印刷质量,对丝网印刷工艺对天线印刷精度的各种影响因素进行了分析,包括网目数、印版特性、刮刀角度等各项参数。通过优化丝印工艺参数,印刷了RFID天线并测量了作为主要参数之一的阻抗,结果表明其阻抗波动较小,丝印工艺可满足天线印刷的质量要求。     

判断二进制树中标签识别完毕的方法

分析了射频识别(RFID)系统阅读器与标签通信的二进制树算法,指出在标签识别过程中,阅读器并不知道是否识别完标签,阅读器会以连续多次没有接收标签响应为依据结束对标签的查询,这样往往会造成标签漏读或浪费时间在已识别完的标签上。基于此分析,提出了判断二进制树中标签识别完毕的方法。该方法通过在阅读器中设置计数器,就可以很好地跟踪标签的识别情况,准确地判断出标签是否识别完毕。分析结果表明,该方法可以准确地判断标签是否识别完毕,增加系统识别效率和可靠性。     

Unobtrusive long-range detection of passive RFID tag motion

This paper presents a novel method for detecting the motion of passive radio-frequency-identification (RFID) tags within the field of a detecting antenna. The method allows the unobtrusive detection of human interactions with RFID-tagged objects without requiring any modifications to existing communications protocols or RFID hardware. We use the response rate (a metric in lieu of the true received RF-signal intensity) at the reader to study the impact of tag translation, rotation, and coupling, as well as environmental effects. Performance is improved by introducing the idea of multiple tags/readers. Movement-detection algorithms are developed and integrated into the RFID monitoring system, and verified by experiments that demonstrate excellent results.     

基于改进ALOHA算法的RFID标签防碰撞研究

目的 为提高射频识别技术(Radio Frequency Identification,RFID)标签识别成功率,以及包装生产线自动分拣效率、智能化水平.方法 以包装生产线检测系统为研究对象,结合RFID技术设计一种自动包装、检测、配送系统.介绍RFID检测系统,主要包括标签、阅读器、天线和控制系统.针对RFID识别过程中标签碰撞问题,提出一种改进ALOHA算法,采用动态预测权值估计标签数目使标签数目与数据帧长度大致相等.通过实验验证ALOHA算法的有效性.结果 实验结果表明,碰撞比率平均值只有1.1％,整个系统的检测成功率可以达到99.6％;所述改进ALOHA算法可以有效避免标签碰撞.结论 该系统能够自动完成检验,并且用时较少,检验过程中正确率较高,具有较高的市场应用价值.     

导电油墨厚度对RFID标签天线辐射效率的影响

为提高RFID电子标签天线的辐射效率,从理论上分析了影响标签天线辐射效率的一系列因素,以偶极子和叠缝隙2种天线为研究对象,研究了导电油墨厚度对RFID标签天线的辐射效率的影响。结果表明:决定天线的辐射效率的是印刷标签天线所用的总油墨量,而不是整个天线结构中不同区域内油墨的分布情况。为实际RFID电子标签生产中导电油墨的控制和改进,提供一些指导。     

小型化超宽带微带天线的设计

本文提出了一种结构简单的小型化超宽带微带天线,尺寸为28mm×30mm．天线采用渐变馈线对酒杯状贴片馈电,接地板采用缺陷地的结构．天线参数采用电磁仿真软件CST进行仿真和优化．测量结果显示该天线在S11小于-10dB时,相对带宽是170．1％（2．4GHz～30GHz）．实际制作了天线的样品并进行了测试,实测与仿真吻合良好．     

一种多天线阅读器定位系统

分析了基于射频识别(RFID)的定位系统的性能,针对现有的RFID定位系统在定位精度、效率、可靠性、成本等方面的不足,提出了一种采用多天线阅读器的定位系统。该系统利用多天线阅读器可扩大单个阅读器定位的覆盖范围,并可根据各接收天线检测的信号强度等信息实现对目标标签的精确定位。通过灵活选择发射天线,可以避免由于阴影效应而带来的信号盲区现象。和传统的单天线阅读器定位方法相比,多天线阵列阅读器定位系统在定位速度、定位精度和抗干扰性上都具有突出的优势。     

Design of high-Q UHF radio-frequency identification tag antennas for an increased read range

In order to increase the radio-frequency identification (RFID) operation distance, read range analysis was performed based on a simple equivalent circuit of the ultra high frequency (UHF)-band passive RFID tag. The analysis shows that a tag with a large Q-factor leads to an increased input voltage in the tag chip and thus enhances the efficiency. Based on this analysis, a compact (37.5 mm 44 mm) RFID antenna employing inductive coupling between the radiation and feeding portions was designed. Simple adjustments of the two structural parameters of the antenna allowed for easy control of the antenna resistance and inductive reactance, from which a high Q-factor requirement could be readily satisfied. For a conjugate match to the tag chip impedance of 11-j127 Omega, a Q-factor of 11.5 was achieved. The designed RFID tag has a 3 dB radar cross-section (RCS) bandwidth of 6.5 , which is wide enough to handle the impedance detuning caused by the material properties of the attached objects. The designed RFID tag antenna was fabricated and a reading range test in an anechoic chamber was performed using two methods. When a measured RCS of the RFID tag was used, the detection distance was 9.8 m for a reader sensitivity of 65 dBm and 4.7 m for a tag sensitivity of 11 dBm. Using a commercially available tag chip, the range test resulted in 4.3 m, which is compatible with the derived range equations. The tag antennas having lower Q-factors (77+j100 Omega and 55+j155 Omega) have also been fabricated, and their measured read ranges were 2.6 and 1.1+m, respectively.     

无源RFID标签用材料研究进展

射频识别(RFID)是一种非接触式的自动识别技术,它是物联网的核心技术。该技术通过射频信号自动识别目标对象并获取相关信息数据,该识别工作不需要人工干预,RFID标签可在各种恶劣环境中工作。RFID的应用非常广泛,尤其是在服装、资产管理等方面的应用最为成熟。RFID标签是RFID技术中必不可少的重要组成部分。随着新材料、新工艺的出现与发展,RFID标签的新产品不断地涌现出来,就近年出现的一些与新材料密切相关的RFID标签新产品与新制造工艺、方法进行了总结。新材料的发展与新工艺的出现为物联网核心技术RFID标签产业提供了新的技术方向和新的经济增长点。     

Propagation characteristics of a 2.45 GHz microwave radio frequency identification system

The propagation characterisation of a 2.45 GHz microwave semi-passive radio frequency identification system in real indoor environment is presented and the effects of three system parameters: the reader orientation, tag antenna designs and propagation environment are evaluated. The unmodulated forward propagation is evaluated by reader signal strength measurements at different tag positions while the modulated backscattered propagation evaluation employs tag read rate as a function of range under horizontal or vertical reader polarisation in an uncluttered or cluttered indoor environment for different tag antenna types. Measured results are used to quantify the variations introduced by the reader polarisation, indoor propagation environment relative to free-space and tag antenna design on the tag response.     

Matching radio frequency identification tag compact dipole antennas to an arbitrary chip impedance

A method for matching dipole antennas to capacitive or inductive arbitrary complex impedances is proposed for ultra high frequency radio frequency identification (RFID) tag antenna designs. It can be applied to straight, capacitive-loaded, meander or any small high-Q dipole topology. For this purpose, design stages are provided with the corresponding formulas. The reflection coefficient simulations and measurements of four implemented prototypes show the expected output when the RFID frequency band, bandwidth, chip impedance and maximum tag size are required as inputs for the method. The eventual S11 < 10 dB bandwidth depends on the chip impedance Q factor and the antenna size. How this bandwidth is manifested in terms of the read range is also discussed. A length ratio of up to 31.1% regarding the standard Λ/2 dipole at resonance is obtained.