RFID技术外文文献翻译

1、外文文献Curre nt RFID Tech nologyThis sect ion describes out of which parts RFID tags con sist of, how they work in prin ciple, and what types of tags do exist. It focuses on how tags are powered and what freque ncy ran ges is used. The sect ion con cludes by coveri ng a few importa nt sta ndards.RFID t

2、ransponders (tags) consist in general of: Micro chip, Antenna, Case, Battery (for active tags only)The size of the chip depends mostly on the Antenna. Its size and form is depe ndent on the freque ncy the tag is using. The size of a tag also depe nds on its area of use. It can range from less than a

3、 millimeter for implants to the size of a book in container logistic. In addition to the micro chip, some tags also have rewritable memory attached where the tag can store updates betwee n read ing cycles or new data like serial nu mbers.A RFID tag is shown in figure 1. The antenna is clearly visibl

4、e. As said before the antenna has the largest impact of the size of the tag. The microchip is visible in the center of the tag, and since this is a passive tag it does not have an internal power sourceIn prin ciple an RFID tag works as follows: the readi ng unit gen erates an electro-mag netic field

5、 which in duces a curre nt into the tag's antenna. The curre nt is used to power the chip. In passive tags the curre nt also charges a conden serwhich assures uninterrupted power for the chip. In active tags a battery replaces the conden ser. The differe nee betwee n active and passive tags is e

6、xpla ined shortly. Once activated the tag receives comma nds from the read ing unit and replies by sending its serial nu mber or the requested in formatio n. In gen eral the tag does not have eno ugh en ergy to create its own electro-mag netic field, in stead it uses back scatteri ng to modulate (re

7、flect/absorb) the field sent by the reading unit. Because most fluids absorb electro-mag netic fields and most metal reflect those fields the read ing of tagsin prese nee of those materials is complicated.During a reading cycle, the reader has to continuously power the tag. The created field is call

8、ed continuous wave, and because the strength of the field decreases with the square of the distanee the readers have to use a rather large power. That field overpowers any resp on sea tag could give, so therefore tags reply on side-cha nn els which are located directly below and above the freque ncy

9、 of the continu ous wave.1. En ergy SourcesWe distinguish 3 types of RFID tags in relation to power or energy: Passive, Semi-passive, Active Passive tags do not have an internal power source, and they therefore rely on the power induced by the reader. This means that the reader has to keep up its fi

10、eld until the tran sact ion is completed. Because of the lack of a battery, these tags are the smallest and cheapest tags available; however it also restricts its reading range to a range between 2mm and a few meters. As an added ben efit those tags are also suitable to be produced by prin ti ng. Fu

11、rthermore their lifespa n is un limited since they do not depe nd on an internal power source.The sec ond type of tags is semi-passive tags. Those tags have an internal power source that keeps the micro chip powered at all times. There are many adva ntages: Because the chip is always powered it can

12、respond faster tore quests, therefore increasing the number of tags that can be queried per second which is important to some applications. Furthermore, since the antenna is not required for collecting power it can be optimized for back scattering and therefore increasing the reading range. And last

13、 but not least, since the tag does not use any energy from the field the back scattered signal is stronger, increasing the range even further. Because of the last two reas ons, a semi-active tag has usually a range larger tha n a passive tag.The third type of tags is active tags. Like semi-active ta

14、gs they contain an internal power source but they use the en ergy supplied for both, to power the micro chip and to gen erate a sig nal on the antenna. Active tags that send sig nals without being queried are called beacons. An active tag's range can be tens of meters, making it ideal for locati

15、ng objects or serving as Iandmark points. The lifetime is up to 5 years.2. Freque ncy BandsRFID tags fall in to three regi ons in respect to freque ncy: Low freque ncy (LF, 30500kHz), High frequency (HF.10-15MHz), Ultra high frequency (UHF, 850- 950MHz, 2.4-2.5GH z, 5.8GHz)Low freque ncy tags are ch

16、eaper tha n any of the higher freque ncy tags. They are fast eno ugh for most applicati ons, however for larger amounts of data the time a tag has to stay in a readers range will in crease. Ano ther adva ntage is that low freque ncy tags are least affected by the prese nee of fluids or metal. The di

17、sadva ntage of such tags is their short readi ng ran ge. The most com mon freque ncies used for low freque ncy tags are 125-134.2 kHz and 140-148.5 kHz.High freque ncy tags have higher tran smissi on rates and ran ges but also cost more tha n LF tags. Smart tags are the most com mon member of this g

18、roup and they work at 13.56MHz. UHF tags have the highest range of all tags. It ranges from 3-6 meters for passive tags and 30+ meters for active tags. In addition the transmission rate is also very high, which allows to read a single tag in a very short time. This feature is importa nt where tagged

19、 en tities are moving with a high speed and rema in only for a short time in a readers ran ge. UHF tags are also more expe nsive tha n any other tag and are severely affected by fluids and metal. Those properties make UHF mostly useful in automated toll collecti on systems. Typical freque ncies are

20、868MHz (Europe), 915MHz (USA), 950MHz (Japan), and 2.45GH z.F reque ncies for LF and HF tags are lice nse exempt and can be used worldwide; however freque ncies for UHF tags differ from country to country and require a permit.3. Stan dardsThe wide range of possible applications requires many differe

21、nt types of tags, often with conflicting goals (e.g. low cost vs. security). That is reflected in the number of standards. A short list of RFID standards follows: ISO11784, ISO11785, ISO14223, ISO10536, ISO14443, ISO15693, ISO18000. Note that this list is not exhaustive. Since the RFID tech no logy

22、is not directly Internet related it is not surpris ing that there are no RFCs available. There cent hype around RFID tech no logy has resulted in an explosi on in pate nts. Curre ntly there are over 1800 RFID related pate nts issued (from 1976 to 2001) and over 5700 patents describing RFID systems o

23、r applications are backlogged.4. RFID SystemsA RFID reader and a few tags are in general of little use. The retrieval of a serial number does not provide much information to the user nor does it help to keep track of items in a product ion cha in. The real power of RFID comes in comb in ati on with

24、a backend that stores additional information such as descriptions for products and where and whe n a certa in tag was sca nn ed. In gen eral a RFID system has a structure as depicted in figure 2. RFID readers scan tags, and then forward the information to the backend. The backend in general consists

25、 of a database and a well defined applicati on in terface. Whe n the backe nd receives new in formatio n, it adds it to the database and if needed performs some computation on related fields. The application retrieves data from the backend. In many cases, the application is collocated with the reade

26、r itself. An example is the checkout point in a supermarket (Note that the given example uses barcodes in stead of RFID tags since they are more com mon; however, the system would behave in exactly the same way if tags were used). When the reader scans the barcode, the application uses the derived i

27、dentifier to look up the current price. In addition, the backend also provides discount information for qualifying products. The backe nd also decreases the nu mber of available products of that kind and notifies the manager if the amount falls below a certain threshold.This sect ion describes how R

28、FID tags work in gen eral, what types of tags exist and how they differ. The three freque ncy ran ges that RFID tags typically use are LF, HF, and UHF. Also the differe nee betwee n passive, semi-passive, and active tags was explained and their advantages and disadvantages were compared. The section

29、 concluded by looking at different standards and showed the great interest of the in dustry by coun ti ng the nu mber of issued and backlogged pate nts US Pate nt Office.翻译:当前的RFID技术该节描述的是RFID标签由哪些部分组成、工作原理和确实存在的标签类型， 关注标签的供电方式和使用频率范围。这部分也总结了一些重要的标准。RFID应答器的一般组成：微芯片、天线、线圈和电池（仅适用于有源标签）。芯片的大小主要取决于天线，它

30、的规模和形式的取决于标签的使用频率，也取决于它的使用面积。它的大小范围可从不到一毫米的植入体大到一本关于集装 箱物流的书。除了微型芯片，有些标签也附有可重写内存，这样标签就可储存更 新阅读周期之间的或新的数据，如序号。如图1所示的RFID标签。天线清晰可见。正如前面所说的，天线对标签大 小的影响最大。在标签的中心可看见的是芯片。因为这是一个无源标签所以无内 部的能源。RFID标签工作原理是如下：阅读单元产生电磁场引导电流流进标签的天线。 该电流用以给芯片提供能源。在无源标签中该电流还为冷凝器充电， 以保证芯片 的不间断供电。在有源标签中电池取代了冷凝器。 有源和无源标签的区别是短期 内的信息阐

31、释。一旦被激活的标签收到阅读的命令它就可以发送序列号或所要求 的信息。总的来说,标签没有足够的能量来创造自己的电磁场，相反它可以采用 反向散射调制（反映/吸收）来产生由阅读单元发射的电磁场。由于大多数流体 吸收电磁场和大多数金属反射这些场，故可使用的标签阅读材料是复杂的在一次循环解读中，阅读器不得不持续给标签供电。它所建立的场将产生连 续波,因为磁场的强度随距离的平方而减少，故阅读器必须有一个相当大的能源。 该场迅速响应标签给的任何指示，因此标签位于正下方的侧渠道可以响应上述 连续波的频率。1. 能源我们辨别三种不同的RFID电子标签的能量或能源：被动、半被动和主动。被动式标签没有内部电源，因

32、此它们的能量来源于阅读器。这意味着阅读器 必须保持磁场直到转换完成。由于没有电池，故这些都是可用的最小和最便宜的 标签。但它的阅读范围可从2毫米和几米。这些标签的另一个好处是适用于印刷生产。此外，因为它不依赖于内部电源，所以它们的寿命是无限的。第二种类型是半被动式标签。这些标签都有内部电源可在任何时候都给微芯片供电。它有许多优点：由于芯片在持续带电的情况下反应迅速，因此可以增加每 秒查询的标签数量，这是非常重要的应用。此外 ，由于天线不需要收集能量，故 可以优化用以反向散射和回归来增加阅读范围。 最后但并非不重要，因为标签不 使用任何磁场能量所以反向散射的信号越强，阅读范围更广。由于最后两个原

33、因， 半被动标签通常比被动标签应用范围更广泛。第三种类型是主动式标签。类似于半主动标签，它的内部也有能源但它的能 源用于两个方面：给微芯片供电和使天线产生信号。主动式标签发送信号而不被 质疑,这被称为信标。主动标签可查询的范围是几十公尺，从而使其适宜于定位对 象或理想标志点。寿命长达 5年的。2. 频带RFID电子标签按照频率分为三个部分：低频（LF,30-500千赫）、高频（HF、 10-15兆赫）、超高频（UHF）, （850-950兆赫,242.5 兆赫,5.8兆赫）。低频标签比任何高频率的标签都便宜。对于大多数应用程序来讲，它们的响应速度很快。但是，留在阅读器的大量标记数据的时间范围将增加。另一个优点是低频标签由于流体的存在或金属的存在而受到的影响最小。这类标签的缺点是它们识别范围很短。最常见的低频标签频率是125-134.2 千赫和 140-148.5十土