UHF频段无源RFID标签阅读距离影响因素分析

在物品识别领域,RFID技术应用的快速发展对RFID标签的读出距离不断提出新的要求.通过对增加UHF900 MHz频段无源电子标签阅读距离的主要方法的研究,着重从电子标签设计中的如下几个要素进行了探讨:天线及标签芯片阻抗匹配、天线及标签芯片的品质因数以及标签基底材料的选择.     

一种低功耗智能传感主动式标签的设计

针对普通标签不能满足一些特定的场合应用需求的问题,提出一种低功耗单片智能传感标签的设计方案。详细阐述了主动式RFID标签的设计思想、硬件结构和软件的设计方法。智能传感标签基于MSP430系列超低功耗单片机进行控制,并结合nRF2401射频芯片以及温湿度传感器SHT21S,实现传感信号的调制解调。该智能传感标签可以定时采集和存储外部温度湿度数据,能够通过无线射频识别通信上传数据并对其进行相应的分析和处理。该标签具有较高的实用性和可靠性,成本低,功耗低,具有良好的应用前景。     

Geometric and Compaction Dependence of Printed Polymer-Based RFID Tag Antenna Performance

Radio frequency identification (RFID) tags with printed antennas are lower in cost but have lower performance than those with metal antennas. Printed antennas can replace metal ones if the performance is increased without raising cost. The performance of printed antennas can be increased if the series resistance in the antennas is lowered. The resistance is dependent on the line thickness and the resistivity of the conductive ink. Printed antennas with different line thicknesses were fabricated to investigate the effect of compaction and thickness on the resistance. The resistance of the printed antenna coils decreased by more than 40% after compaction, while the inductance and the parasitic capacitance were unchanged. RFIDs with compacted printed antennas were found to have significantly increased read range. RFIDs with thick printed antennas were fabricated and tested. These RFIDs were shown to have read ranges comparable to the RFIDs with copper wire antennas. Moreover, a geometry-independent plateau for the read range was found. The presence of a plateau is valuable for thick-line printed antenna since the plateau will enable the usage of low precision printing techniques to lower tag fabrication cost.     

Reliability of washable wearable screen printed UHF RFID tags

Wearable antennas have an enormous potential in future welfare, healthcare, and childcare applications. These applications require the antenna to be an integral and unnoticeable part of clothing and to be able to endure different environmental conditions and repeated washing. We manufactured UHF RFID tags by screen printing polymer thick film ink antennas on two different fabric substrates and tested the effects of different types of washing cycles on two key properties of wearable passive UHF RFID tags: threshold power and theoretical read range. Despite the detrimental impact of the washing cycles and detergents, the RFID tags remained wirelessly readable at the distances of beyond 1.3 m, which is satisfactory for many field applications.     

Performance of Printed Polymer-Based RFID Antenna on Curvilinear Surface

The performance of flexible printed RFID tags affixed onto cylindrical containers is dependent on the inductive behavior of the bent antenna on the tag. Conductive polymeric coil antennas were screen printed onto flexible substrates, and the coil resistances, the inductances, and the S-parameters of the antenna coils were measured and analyzed. The RFID dies were mounted onto the antenna coils and the read ranges were characterized as a function of curvature. The results show that the coil inductance decreased slowly with increasing curvature, and the maximum read range of the tags was markedly reduced with the curvature. The decrease in the coil inductance and the maximum read range were hypothesized to vary with the projected bent coil area instead of the geometric coil area. Experimental results confirmed that the maximum read range of an RFID tag affixed on a curvilinear surface can be predicted by the classical inductive coupling model with the bent projected coil area. On the basis of the experimental and analytical results, a reading reliability factor of two is proposed as a design parameter for flexible RFID tags.     

低成本射频识别标签模拟前端分析与设计

提出一种新的低成本射频识别标签模拟前端,同时兼容ISO 14443A和ISO 14443B协议.相比于传统模拟前端,本设计采用面积更小的单线圈天线代替传统大面积多圈天线,使得标签的封装成本大幅度降低.考虑到单线圈天线的性能降低,设计了一个新的具有高效率低启动电压的电荷泵整流电路.整体电路采用SMIC 0.18μm EEPROM工艺实现,测试结果显示电荷泵驱动120kΩ等效负载时,整流效率达到36%,输入交流幅度仅0.5V时,输出电压达到电路工作电压1V.标签的阅读距离可以达到22cm.     

Design of a RFID System for Real-Time Tracking of Laboratory Animals

In this paper, a real-time RFID system capable of tracking laboratory animals is designed and implemented. Four passive RFID tags based on low frequency are designed and implemented. The tags can be read by any RFID reader that operates on the low frequency range 125–134 kHz. The tags are designed through the investigation of various antenna, encoding, modulation, and energy harvesting techniques. The tag receives the electromagnetic signal via the antenna, and converts it to a DC signal that the microcontroller can use to manipulate the electromagnetic signal with the data such that the reader can decode the unique tag identifier. RFID sensors are designed and implemented to collect data from various monitored areas of a semi natural environment. The data is sent to a central data coordinator for pre-processing and middleware for data error checking, display and storage. The RFID system can successfully detect and store movement data in real time. A read range of 14.5 cm is achieved.     

Analysis and design of power efficient semi-passive RFID tag

The analysis and design of a semi-passive radio frequency identification(RFID) tag is presented.By studying the power transmission link of the backscatter RFID system and exploiting a power conversion efficiency model for a multi-stage AC-DC charge pump,the calculation method for semi-passive tag's read range is proposed.According to different read range limitation factors,an intuitive way to define the specifications of tag's power budget and backscatter modulation index is given.A test chip is implemen...     

Applicability of Metallic Nanoparticle Inks in RFID Applications

Radio frequency identification (RFID) antennas for HF and UHF frequencies are ink-jet printed using commercially available silver nanoparticle ink. Quality factors of 5.3 and 9.4 are obtained for coil antennas targeted for 13.56 MHz when the printing and sintering process is repeated two and three times, respectively. The measured maximum effective aperture of the printed UHF antenna is only some decibels lower than that of an equivalent etched copper antenna and the maximum reading distance with 0.5 W (ERP) transmitted power is 3 m for continuous reading. These results suggest that obtaining a low enough series resistance for printed coils is challenging while printed RFID antennas for UHF do not set as strict requirements on conductivity. With a perfectly optimized structure, a UHF tag antenna printed in just one layer of ink can be practically equal in performance with the traditional etched copper and aluminum tags.      

An Ultra-Low-Power Long Range Battery/Passive RFID Tag for UHF and Microwave Bands With a Current Consumption of 700 nA at 1.5 V

We present for the first time, a fully integrated battery powered RFID integrated circuit (IC) for operation at ultrahigh frequency (UHF) and microwave bands. The battery powered RFID IC can also work as a passive RFID tag without a battery or when the battery has died (i.e., voltage has dropped below 1.3 V); this novel dual passive and battery operation allays one of the major drawbacks of currently available active tags, namely that the tag cannot be used once the battery has died. When powered by a battery, the current consumption is 700 nA at 1.5 V (400 nA if internal signals are not brought out on test pads). This ultra-low-power consumption permits the use of a very small capacity battery of 100 mA-hr for lifetimes exceeding ten years; as a result a battery tag that is very close to a passive tag both in form factor and cost is made possible. The chip is built on a 1-mum digital CMOS process with dual poly layers, EEPROM and Schottky diodes. The RF threshold power at 2.45 GHz is -19 dBm which is the lowest ever reported threshold power for RFID tags and has a range exceeding 3.5 m under FCC unlicensed operation at the 2.4-GHz microwave band. The low threshold is achieved with architectural choices and low-power circuit design techniques. At 915 MHz, based on the experimentally measured tag impedance (92-j837) and the threshold spec of the tag (200 mV), the theoretical minimum range is 24 m. The tag initially is in a "low-power" mode to conserve power and when issued the appropriate command, it operates in "full-power" mode. The chip has on-chip voltage regulators, clock and data recovery circuits, EEPROM and a digital state machine that implements the ISO 18000-4 B protocol in the "full-power" mode. We provide detailed explanation of the clock recovery circuits and the implementation of the binary sort algorithm, which includes a pseudorandom number generator. Other than the antenna board and a battery, no external components are used.     

Design of an electronic label for logistics temperature monitoring with low power consumption

There are many problems when traditional temperature sensing radio frequency identification (RFID) tags are applied to logistics temperature monitoring, such as inconvenient data reading, large power consumption, and low bandwidth. Therefore, a low-dissipation electronic tag is designed in this paper to solve the above problems. The electronic tag and the portable temperature recorder were placed in the same position in the same refrigeration unit, and the temperature of the same space was recorded at the same time. The data measured by the designed electronic tag was used as the measured value, and the data measured by the portable temperature recorder was used as the standard value. The correlation coefficient between the two was calculated to be 0.866 9, the root mean square error (RMSE) was 0.796 7 °C, and the average relative deviation (ARD) was 16.21%. Therefore, the electronic tag designed in this study can meet the requirements of users for temperature monitoring and recording. The temperature control switch designed in this study can disconnect the power supply to single chip microcomputer (SCM) and other modules when the temperature is in the range of normal threshold, so that the power consumption is further reduced and the cost is reduced. The results of this study laid a foundation for the development of low-cost and easy-to-use temperature monitoring technology in the logistics process.     

Flexible RFID Tag Metal Antenna on Paper‐Based Substrate by Inkjet Printing Technology

A reliable and low‐cost solution‐processing procedure to synthesize a highly adhesive flexible metal antenna with low resistivity for radio‐frequency identification device (RFID) tags on paper substrates via inkjet printing combined with surface modification and electroless deposition (ELD) is demonstrated in this paper. Through the surface modification of colloidal solution of hydrolyzed stannous chloride and chitosan solution, the paper‐based substrate is able to reduce the penetration rate of ink and further increase the adsorption amount of silver ions, which could create a catalytic activating layer to catalyze the subsequent ELD of a conductive deposited metal antenna. The resulting metal antenna for RFID tags presents good adhesive strength and low resistivity of 2.58 × 10^?8 Ω·m after 40 min of ELD, and maintains a reliable reading range of RFID tags even after over 1000 times of bending and mechanical stress. Consequently, the developed technology proposed allows for cheap, efficient, and massive production of metal antenna for paper‐based RFID tags with excellent mechanical and electrical properties. Furthermore, this process is especially advantageous for the fabrication of next‐generation flexible electronic devices based on paper substrates.     

A study on the performance and reliability of magnetostatic actuated RF MEMS switches

The magnetostatic radio frequency micro-electro-mechanical system switch is a special latching type of switch that possesses substantially high performance due to low loss, high linearity, and broad bandwidth. This new technology targets applications where high electrical performance and reliability are required in a harsh environment. A study on switch performance and reliability under different environmental conditions is crucial to its applications. In order to assess the reliability under desired environmental and operational conditions, comprehensive humidity and temperature reliability tests were conducted. The humidity test was conducted under high relative humidity and temperature cycling conditions. The thermal aging test was conducted at different temperature levels, which was used to study the fitness of lifetime distribution and validate the suitability of Arrhenius model that can be used for the lifetime prediction at normal operation temperature.     

标签分布疏密状态变化情形下超高频天线设计方法研究

针对标签分布疏密程度的变化会导致其天线与负载的阻抗匹配关系改变进而影响系统性能的问题。该文结合电磁波传播理论和射频识别(RFID)工作原理,导出了标签分别处于稀疏和密集分布状态下的RFID系统通信链路模型;结合变压器模型和二端口网络分析方法,推导了标签密集分布状态时标签天线的互阻抗表达式;利用功率传输系数和反向散射调制因子,分析了标签分布疏密程度对RFID系统性能的影响;基于加载条匹配原理,提出一种适用于分布疏密状态变化情形的标签天线优化设计方法。仿真实验和实际测量结果表明,标签密集分布时,改进标签的性能较原型标签提升16%;标签稀疏分布时,改进标签的性能达到原型标签的96%。     

High efficiency, high power 808nm laser array and stacked arrays optimized for elevated temperature operation

Operation of 808-nm laser diode pumping at elevated temperature is crucial to many applications. Reliable operation at high power is limited by high thermal load and low catastrophic optical mirror damage (COMD) threshold at elevated temperature range. We demonstrated high efficiency and high power operation at elevated temperature with high COMD power. These results were achieved through device design optimization such as growth conditions, doping profile, and materials composition of the quantum-well and other layers. Electrical-to-optical efficiency as high as 62% was obtained through lowered threshold current, lowered series resistance and increased slope efficiency. The performance of single broad-area laser diodes scales to that of high power single bars on water-cooled copper micro-channel heatsinks or eonductively-cooled CS heatsinks. No reduction in bar performance or significant spectral broadening is seen when these micro-channel coolers are assembled into 6-bar and 18-bar CW stacks for the h     

纸基柔性RFID标签金属天线制备

纸张基材具备的多孔特性使其表面的液体材料产生了渗透、扩散等现象,因此在纸基的表面利用化学镀形成RFID标签金属天线极为困难。针对这个问题,文中采用氯化亚锡胶体溶液对纸张表面进行处理以避免转印油墨渗透。为进一步提高RFID标签天线金属层的导电性和附着力,采用壳聚糖溶液处理纸张基板表面以引入对催化离子具有吸附性的功能基团。SEM、XRD、EDS和附着力测试证明,文中所制备RFID标签天线的金属层表面具有致密、结晶度高、附着力良好、电阻率低(2.58×10 ^-8 Ω·cm)且机械性能良好(1 000次弯曲)等优点。     

改进型帧时隙ALOHA防碰撞算法研究

为进一步提高RFID系统中电子标签防碰撞算法的识别效率,对帧时隙ALOHA防碰撞算法的性能进行分析,提出一种结合精确标签估计和二进制搜索的改进型帧时隙ALOHA算法.将识别过程分为标签估计和标签识别两个阶段,在标签估计算法中引入碰撞概率上、下限参数,并精确估计标签数量对初始帧时隙大小进行优化;在标签识别阶段,利用二进制搜索算法对时隙内的碰撞标签进行快速识别.通过对识别过程进行仿真结果表明:改进的算法改善了防碰撞性能,提高了RFID系统的标签识别效率.     

Ink formulation and low‐temperature incorporation of sodium to yield 12% efficient Cu(In,Ga)(S,Se)2 solar cells from sulfide nanocrystal inks

Solution phase deposition methods offer great potential for low‐cost photovoltaic device fabrication. We have previously developed a method for copper indium gallium disulfoselenide (CIGSSe) device fabrication based on drop‐casting copper indium gallium disulfide (CIGS) nanocrystals in a toluene or hexane‐based ink followed by chalcogen exchange in elemental selenium vapor at 500 °C. By starting with the chalcopyrite or sphaelerite phase of CIGS nanocrystals with controlled stoichiometry, superior composition uniformity can be achieved inherently. Here, we present a dramatic improvement in ink formulation using alkanethiol as the solvent, which enables the ability to create uniform nanocrystal coatings over large areas using a simple knife coating technique. In addition, we show a major improvement in device performance by a simple and low‐temperature method of incorporating sodium into the CIGSSe film based on soaking the films in aqueous NaCl solution. The addition of sodium plays an important role in improving the structural properties of the resulting CIGSSe films, where large and densely packed grain can be obtained. The improved film morphology significantly reduces recombination losses in the resulting device leading to a dramatically enhanced device performance. With the use of standard glass/Mo/CIGSSe/CdS/i‐ZnO/ITO device structure, photovoltaic devices yield total area power conversion efficiency as high as 12.0% under AM1.5 illumination without an anti‐reflection coating. Copyright © 2012 John Wiley & Sons, Ltd.     

Photoactivation of the processes of formation of nanostructures by local anodic oxidation of a titanium film

Experimental results on the conditions of activation of probe nanolithography of a thin titanium film by means of local anodic oxidation are reported. It is established that ultraviolet stimulation reduces the geometric dimensions of nanometric oxide structures. The stimulation is accompanied by an increase in the amplitude and duration of the threshold voltage pulse, correspondingly, from 6 to 7 V and from 50 to 100 ms at the relative humidity 50%. The experimental data on the effect of the cantilever coating material and substrate temperature on the geometric dimensions of nanometric oxide structures are reported.     

Printed Transistors on Paper: Towards Smart Consumer Product Packaging

The integration of fully printed transistors on low cost paper substrates compatible with roll‐to‐roll processes is demonstrated here. Printed electronics promises to enable a range of technologies on paper including printed sensors, RF tags, and displays. However, progress has been slow due to the paper roughness and ink absorption. This is solved here by employing gravure printing to print local smoothing pads that also act as an absorption barrier. This innovative local smoothing process retains desirable paper properties such as foldability, breathability, and biodegradability outside of electronically active areas. Atomic force microscopy measurements show significant improvements in roughness. The polymer ink and printing parameters are optimized to minimize ink absorption and printing artifacts when printing the smoothing layer. Organic thin film transistors (OTFT) are fabricated on top of this locally smoothed paper. OTFTs exhibit performance on par with previously reported printed transistors on plastic utilizing the same materials system (pBTTT semiconductor, poly‐4‐vinylphenol dielectric). OTFTs deliver saturation mobility approaching 0.1 cm²V^–1s^–1 and on‐off‐ratio of 3.2 × 10⁴. This attests to the quality of the local smoothing, and points to a promising path for realizing electronics on paper.