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RFID radio frequency identification is a non-contact automatic identification technology, which automatically recognizes the target object and obtains related data through radio frequency signals. The identification work does not require manual intervention and can work in various harsh environments. RFID technology can identify high-speed moving objects and can identify multiple tags at the same time, and the operation is quick and convenient.
Ferguson, the chief scientist of the Accenture Lab, believes that RFID is a breakthrough technology: “First, it can identify a single very specific object, instead of only identifying a type of object like a barcode; second, it uses radio frequency, which can be The data is read through external materials, and the barcode must be read by laser; third, multiple objects can be read at the same time, while the barcode can only be read one by one. In addition, the amount of stored information is also very large. ”
The most basic RFID system consists of three parts:
Tag: It is composed of coupling components and chips. Each tag has a unique electronic code and is attached to the object to identify the target object;
Reader: A device that reads (and sometimes writes) tag information, which can be designed as a handheld or fixed type;
Antenna: Transmit radio frequency signals between the tag and the reader.
A complete system also needs to have: a data transmission and processing system.
The basic working principle of RFID technology is not complicated: after the tag enters the magnetic field, it receives the radio frequency signal from the reader, and uses the energy obtained by the induced current to send out the product information stored in the chip (Passive Tag, passive tag or passive tag) , Or actively send a signal of a certain frequency (Active Tag, active tag or active tag); after the reader reads and decodes the information, it is sent to the central information system for relevant data processing.
RFID is one of the ten strategic technologies recommended for enterprises to consider introducing in 2005, and middleware can be said to be the hub of RFID operations because it can accelerate the advent of key applications.
The potential of the RFID industry is endless, with applications ranging from manufacturing, logistics, medical care, transportation, retail, national defense, and so on. Gartner Group believes that RFID is one of the ten strategic technologies that companies are recommended to consider introducing in 2005. However, the key to its success is the price of tags, antenna design, band standardization, and equipment certification. It is necessary to have key application software (Killer Application) in order to promote quickly. And the middleware (Middleware) can be called the hub of RFID operation, because it can accelerate the advent of key applications.
According to estimates by retail analysts at Sanford C and Bernstein, Wal-Mart can save US$8.3 to 500 million per year by adopting RFID, most of which are the labor costs saved by not having to manually check the barcodes of incoming goods. Although some other analysts believe that the figure of $8 billion is too optimistic, there is no doubt that RFID can help solve the two biggest problems in the retail industry: out of stock and wastage (products lost due to theft and disrupted supply chain) , And now for theft alone, Wal-Mart’s losses in a year are almost 2 billion U.S. dollars. If a legitimate company’s turnover can reach this number, it can be ranked 694th in the list of the 1,000 largest companies in the United States. . Research institutions estimate that this RFID technology can help reduce theft and inventory levels by 25%.
Automatic identification of railway car number is the most common application of radio frequency identification technology.
The highway automatic toll collection system is one of the most successful applications of radio frequency identification technology, which fully embodies the advantages of non-contact identification. The toll payment is completed while the vehicles pass through the toll station at high speed, which solves the bottleneck problem of traffic, increases the speed of vehicles, avoids congestion, and improves the efficiency of toll settlement.
Radio frequency identification technology provides fast, accurate and automated means for tracking, managing and monitoring goods. Automatic container identification with radio frequency identification technology as the core has become the world’s largest cargo tracking management application.
Radio frequency identification technology has many successful applications in logistics links such as warehousing and distribution. With the research and development of unified standards for radio frequency identification technology in the open logistics link, the logistics industry will become the industry that benefits most from radio frequency identification technology.
Radio frequency identification card is a major application of radio frequency identification technology. The function of the RFID card is equivalent to an electronic wallet, realizing non-cash settlement. The current main application is in transportation.
It is mainly used in the automated assembly line of large factories to realize automatic control and monitoring, improve production efficiency and save costs.
Radio frequency identification technology can be used for animal tracking. In large-scale breeding plants, the use of radio frequency identification technology to establish breeding files, vaccination files, etc., can achieve the purpose of efficient and automated management of livestock, and at the same time provide a guarantee for food safety. Radio frequency identification technology can also be used for pigeon racing, horse racing identification, etc., to accurately determine the time of arrival.
The passive RFID tag itself does not have a battery, and relies on the electromagnetic energy sent by the reader to work. Because of its simple structure, economical and practical, it has been widely used. Passive RFID tags are composed of RFID IC, resonant capacitor C and antenna L. The antenna and capacitor form a resonant circuit, and the carrier frequency of the card reader is tuned to obtain the best performance.
Manufacturers mostly follow the specifications of the International Telecommunication Union. There are 6 kinds of frequencies used by RFID, namely 135KHz, 13, 56MHz, 43, 3-92MHz, 860-930MHz (ie UHF), 2, 45GHz and 5, 8GHz. Passive RFID mainly uses the first two frequencies.
There are two types of RFID tag antennas: (1) wire-wound inductive antenna; (2) embossed or printed coiled antenna on a dielectric substrate. The antenna form is determined by factors such as carrier frequency, label packaging form, performance and assembly cost. For example, when the frequency is less than 400KHz, mH-level inductance is required. This type of antenna can only be made with wire-wound inductors; when the frequency is 4~30MHz, only a few loops and a few turns of wire-wound inductors are sufficient, or use a dielectric substrate Carved antenna.
After selecting the antenna, the next step is how to attach the silicon IC to the antenna. There are also two basic methods for IC attachment: (1) Using a chip-on-board (COB); (2) directly attaching the bare chip to the antenna. The former is often used for wire-wound antennas; the latter is used for engraving antennas. CIB encapsulates the resonant capacitor and RFID IC together in the same case, and the antenna is connected to the two external terminals of the COB by soldering iron or welding process. Since most COBs are used for ISO cards, a card that meets the ISO standard thickness (0, 76) specifications, the typical thickness of COB is about 0, 4mm. Two common forms of COB packaging are IOA2 (MOA2) adopted by IST and WorldⅡ adopted by HEI in the United States.
Direct bonding of bare chips reduces intermediate steps and is widely used in low-cost and high-volume applications. There are also two methods for direct bonding, (1) wire bonding; (2) flip-chip technology. When using the flip-chip process, special solder balls need to be made on the chip pads, the material is gold, and the height is about 25 μm, and then the solder balls are flip-mounted on the printed traces of the antenna. The wire bonding process is relatively simple, the bare chip is directly soldered on the antenna with the wire, and the bonding area is sealed with black epoxy resin. For small batch production, the cost of this process is lower; for mass production, it is better to adopt the flip-chip process.
The performance of a wireless RFID tag is greatly affected by the size of the tag, modulation form, circuit Q value, device power consumption and modulation depth. Here is a brief introduction to its working principle.
There is a 154-bit memory inside the RFID IC to store tag data. There is also a modulation gate control tube (CMOS) with extremely low on-resistance inside the IC, which works at a certain frequency. When the card reader emits electromagnetic waves to make the inductive voltage of the tag antenna reach VPP, the device works and sends the data back in Manchester format.
Data transmission is accomplished by tuning and de-tuning the external resonance circuit. The specific process is as follows: When the data is at a logic high level, the gate control tube is turned off, and the tuning circuit is tuned to the cut-off frequency of the card reader. This is the tuning state, and the induced voltage reaches the maximum value. In this way, tuning and de-tuning generate an amplitude modulation signal on the tag coil, and the card reader detects the voltage waveform envelope to reconstruct the data signal from the tag.
The switching frequency of the gate control tube is 70KHz, and it takes about 2, 2ms to complete all 154 bits of data. After sending all the data, the device enters a 100 ms sleep mode. When a tag enters sleep mode, the card reader can read the data of other tags without any data conflict. Of course, this function is affected by the following factors: the distance from the tag to the reader, the orientation of the two, the movement of the tag, and the spatial distribution of the tag.
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