With the promotion and application of RFID technology in various fields, the requirements for electronic tags and readers are gradually refined. From the requirements for reading and writing distance of electronic tags, they can be roughly divided into two categories:
The first type is a close range automatic identification system. After years of development of RFID technology, the proximity RFID technology with a frequency of up to several tens of centimeters and a frequency of 13.56 MHz or less has been relatively mature. Generally, people hold electronic tags (cards) or readers, so that the two are directly close to each other for reading and writing. At present, it is used in a large amount, such as China's second-generation smart ID card, IC card electronic ticket for bus and subway, and access control system for office workers.
The second type is a long-distance automatic identification system, which reads and writes electronic tags at distances ranging from a few meters to more than ten meters. If you want to close the moving or moving objects such as moving vehicles, baggage on the conveyor belt, workpieces on the assembly line, you must stop them, which will not only reduce efficiency, but even impossible for some applications. Long-distance RFID technology is an essential means for automatic data collection in logistics, production automation, supply chain management and traffic management industries, and the establishment of a networked management information platform. The application of long-distance RFID products has become an unstoppable trend.
The long-range RFID system uses three operating frequency bands: the 840MHz to 960MHz UHF band (UHF), the 2.45GHz band, and the 5.8GHz band. In the early days, due to the limitation of the level of RFID technology, the circuit of the electronic tag must be powered by the battery. This brings problems such as expensive electronic tags, inconvenient use and maintenance, and limited life, which limits the application and promotion of RFID systems. In the late 1990s, semiconductor integrated circuits reached a very high level of integration and power consumption, and monolithic integrated circuits for passive electronic tags were fabricated in the UHF and 2.45 GHz bands. The electromagnetic wave energy radiated from the reader antenna can be used to drive the tag circuit to work. Passive electronic tags in the 2.45 GHz band have a very close recognition distance, while the UHF band has a recognition distance of more than 10 meters, which has become the mainstream of long-distance passive identification systems. Due to the relatively complicated technology, it is difficult to manufacture passive and long-distance electronic tags. The price of electronic tags is dozens of times that of passive tags. The system of highway tolls in China and Europe and Japan still The active 5.8 GHz system is used.
UHF RFID system is entering high-speed growth mode. UHF long-distance automatic identification technology has the ability to read multiple tags at one time, has strong penetrability, can be read and written multiple times, and has large memory capacity. The cost of passive electronic tags is low and the volume is small. It is easy to use, reliable and has a long life. It can work under the condition of high-speed movement of vehicles or other marked objects, and withstand the harsh outdoor environment. It has received the attention of all countries in the world. In recent years, due to the promotion of the US Department of Defense and large European and American companies, the establishment of automatic identification international standards, coupled with the decline in the price of UHF electronic tags, has greatly reduced the application threshold of RFID technology. The application field of UHF long-distance automatic identification technology has gradually changed from vehicle-related applications to various fields of national economy such as modern logistics, e-commerce, traffic management, e-government and military management. UHF long-distance automatic identification has begun to enter the high-speed growth period. .
Driven by the rapid economic development and the use of information technology to improve efficiency and quality in the whole society, in 2006, 15 ministries and commissions including the Ministry of Science and Technology jointly published a white paper on China's radio frequency identification (RFID) technology policy, which is the future development of RFID technology and industry. A systematic guide is provided. After more than a decade of development, China's automatic identification industry has begun to take shape, and the RFID industry chain has basically taken shape. In the mid-1990s, Shenzhen Yuanwanggu Technology Co., Ltd. and other units developed the automatic identification system for railway vehicles. Represented by Xinyuan Modern in Sichuan Province, the “Automatic Vehicle Identification Management System†was established in Shenzhen Customs since 1997 to manage transit vehicles. And since 2001, the original active card system has been changed to an ultra-high frequency passive card system.
In the fall of 2001, Shenzhen Renyi Investment Development Co., Ltd. took the lead in developing the reader/writer and system in accordance with ISO/IEC18000-6B, and successfully used it in Shenzhen Customs electronic transit channel management and other projects. Since then, Nanjing Sanbao Group Ruifu Technology Co., Ltd. and Shenzhen Xianshi Technology Co., Ltd. have all invested in the development of long-distance identification electronic tags and reader systems with independent intellectual property rights, forming a preliminary industrial scale, not only It has provided a large number of electronic tags and readers for the country, and has also been exported to many countries in the United States, Canada, Mexico, Brazil and the Middle East, becoming an important member of the international long-distance passive identification system family.
The long-distance automatic identification technology of passive electronic tags is relatively complicated. At present, the production scale of each company is small and the production cost is high. Among the many RFID companies in the country, various agencies or foreign enterprise branches and system integration and application system development enterprises account for nearly 90%, truly engaged in the development of RFID core technology, less than 10% of enterprises with independent intellectual property rights, is China The weakest link in the RFID industry. In response to the current status of this technology and industrialization, China's Ministry of Science and Technology has listed "Radio Frequency Identification (RFID) Technology and Applications" as a major project of the National High Technology Research and Development Program (863 Program), and organized a group of RFID common foundations and forward-looking. Key technologies for industrialization and application of key technologies, establish China's RFID technology independent innovation system, public application service system and RFID standard system, build an industrial chain with independent intellectual property rights technology, reduce the production cost of key equipment such as electronic tags and readers Accelerate the development of application software, increase the intensity of promotion and use, and meet the urgent needs of logistics, transportation, production management and national security. Under the premise of accelerating the development of long-distance automatic identification technology at home and abroad, there are the following development trends worthy of attention:
I. ISO/IEC18000-6C may become the de facto UHF RFID space interface standard With the beginning of the large-scale application of RFID in the global logistics industry, the unification of RFID standards has been widely recognized by the industry. EPC Global is jointly established by UCC Product Coding Organization of North America and European EAN Product Standards Organization. It has hundreds of members around the world and is supported by retail giant Wal-Mart, manufacturing giant Johnson & Johnson, Procter & Gamble and other multinational companies. European manufacturers have the opposite strength. In 2006, EPC Gen2 was incorporated into the ISO/IEC18000-6 standard jointly by the International Organization for Standardization (ISO) and the International Electrotechnical Organization (IEC), called ISO/IEC18000-6C. In the ultra-high frequency (UHF) frequency band, the spatial communication interface standard ISO/IEC18000-6, A, B and C, for historical reasons, most of the B class is used in the transportation field, while the C class is mainly used for logistics and production management. And the field of supply chain management. However, the speed of the C-type label is higher than that of the B-class, the price is low, the number of production and sales far exceeds the B-class, and there is a tendency to gradually replace the B-class completely, which may become the de facto UHF long-distance passive automatic identification system. The only international standard, not only in the field of logistics, production management and supply chain management, but also in the field of traffic management.
The electronic tag chips conforming to ISO/IEC18000-6, A, B and C have been mass-produced in many integrated circuit companies such as Philips and TI. Fudan Microelectronics of China has also announced the successful development. The following table lists the specifications of several UHF band electronic tag IC products from Philips (now NXP):
Second, the industry needs to develop a variety of electronic tags In an RFID system, electronic tags generally account for 60% to 70% of the total investment. The investment in readers and computer systems is one-off, but the number of electronic tags and their expansion over time will increase year by year. According to a research report by an authoritative consultancy, by 2008, the world will use 20 billion RFID tags per year. In 2010, the global RFID market will reach 300 billion US dollars. The most popular market for RFID tags in the next few years is the packaging/supply chain market. By 2008, there will be approximately 15.3 billion containers and pallet labels, and 6.8 billion RFID tags for drugs, luggage, animals, books and bills.
In order for UHF's automatic identification system to recognize a long distance, it is necessary to improve the performance of electronic tags and readers at the same time, and electronic tags are a key link. The electronic tag consists of a housing or a surface layer, an antenna, a substrate on which the antenna is located, an integrated circuit, an integrated circuit, and an antenna connection circuit. The performance depends on the antenna of the electronic tag, the integrated circuit of the electronic tag, and their package. The most difficult point of UHF electronic tags is that the electronic tags are embedded or attached to different shapes and types of products. The surface of the objects attached to the tags is also part of the electronic tag antenna, which affects the electrical parameters of the tag antenna. The diversity and uncertainty of the environment in which the label is used, combined with the shape and size of the label, are limited by the requirements of the application, making the design of the tag antenna particularly difficult, and can only be determined experimentally in many cases.
Due to the different applications of electronic tags, there are different requirements. For example, as an automobile logo, after the electronic tag is installed on the car, it becomes the electronic ID card of the car, and becomes an "electronic tag" in the management sense. It must not be dismantled and establish a unique correspondence with the car. Disposable electronic labels for logistics and baggage parcels are used in large quantities and require low cost. Electronic tags used in production process management often need to be able to be recycled. Some requirements can be applied to metal surfaces, and some require high temperature, low temperature, high humidity, mechanical shock and other harsh environments. The diversity of application requirements brings diversity in the form of electronic labels. The table below lists the common types of electronic tags that need to be developed to address a wide range of products to meet a variety of needs.
Third, long-distance passive identification readers are further integrated and modularized With the expansion of the application of long-distance passive identification systems, the global market for long-range passive readers is also growing rapidly. The global RFID reader market will continue to grow at an annual growth rate of around 30%. By 2008, the EPC reader market will reach US$1.14 billion, and the market for other close-range readers will reach US$750 million in the same year.
However, the price of long-distance passive identification system equipment in China is much higher than that of short-distance systems. The main reason is that the production scale is small. With the expansion of application, the development and production costs will be greatly reduced. Long-range passive systems involve microwave technology, making design, production, and commissioning tests difficult. With the deepening of applications, the requirements of readers can vary widely, such as antenna form, number of antennas, mechanical structure, data communication mode, status display, environmental conditions and power supply. If these different requirements are met, from the beginning of circuit design, the development of a variety of readers, and each production volume is not large, it will be very uneconomical, the cost will be difficult to reduce. In order to reduce the complexity of design, production and debugging, an important task is to improve the integration of the reader circuit and modularize the common components. The current trend is to modularize the core circuit of the reader and then combine the reader circuit modules into readers that meet various needs. For example, the US company Sirit has developed the INfinity 210 and SM9311 multi-protocol reading and writing modules. Recently, Shenzhen Xianshi Company has developed a 40 mm wide and 60 mm long reader module using the Intel R1000 EPC protocol ASIC.
Fourth, UHF RFID readers from the "car-related" application to the "related" applications as the main electronic tag price can only be reduced to less than 1% of the cost of the mark, it is possible to promote a large number. In the previous stage, due to the price of UHF electronic tags ranging from a few to several tens of dollars, the application mainly focused on the identification of high-value items such as automobiles and railway locomotives, and was applied to highway non-stop charging, parking lot management, agencies and community vehicles. Vehicle-related applications such as access control, bus scheduling, and vehicle transit supervision. Now the EPC electronic label has been reduced to about 20 cents. The one-time label can be used for pallets and cartoon boxes at the first level. The valuable items can be identified at the first level. Multiplexed labels can be used for item identification in production and distribution processes. This greatly expands the application range of the UHF long-distance automatic identification system, and enters a wide range of areas of the national economy such as logistics, transportation, production management, medical care and national security, and will be an avalanche-like growth trend. The technical requirements for UHF RFID readers for car-related applications are completely different from those of "related" applications. The requirements for reading and writing of the vehicle-related readers are far from being read and written, ensuring that they can be correctly identified under the conditions of high-speed driving of the vehicle, and that it is required to be directly connected to the road traffic control device and the computer. UHF RFID readers for "involvement" applications differ greatly from vehicle-related application readers due to different object objects, different label installation locations, and different control point settings for logistics.
The requirements for the application of UHF RFID readers are as follows:
1. In the process of handover, transmission and transportation, the position and orientation of the items can be changed during the process of handover, transmission and transportation. It is impossible to stick the electronic label on the window glass forever. Forward direction. Therefore, the logistics application UHF RFID reader must adapt to the randomness of the position and orientation of the electronic tag, and can be read from different directions. A better approach is to design a door-frame or tunnel multi-antenna reader. In order to avoid the electromagnetic waves emitted by different antennas from interfering with each other, these antennas should work in a time division system, which is equivalent to the electromagnetic wave beam scanning around a center of the ring, so that the labels attached to different faces can be read.
Electronic tags are usually linearly polarized. In order to ensure that tags of various polarization orientations can be read, the antenna of the stream reader should use a circularly polarized antenna.
2. Efficient multi-tag arbitration capability The physical size of the car is large. Within the effective coverage of the UHF RFID reader, there are not many opportunities for multiple tags, and even if there are, the number will not be much. However, in logistics applications, it is extremely common to have dozens of electronic tags in the field of view of UHF RFID readers. Therefore, logistics UHF RFID readers must have strong multi-tag arbitration capability with high speed and accuracy. . The ISO18000-6C electronic tag has a communication speed of up to 640Kbits/S, which creates conditions for high-speed arbitration. Therefore, it has obvious advantages for logistics applications ISO18000-6C electronic tags.
3. Working capacity in high reader density environment In logistics management and other applications, there may be multiple readers with the same frequency range in one area, and the microwave electromagnetic fields cover each other to form mutual interference. The method of the problem is mainly to make the scientific working segmentation of the reader's working time or working frequency range or antenna radiation range. For example, the reader's LBT function (Listen Before Talk), avoid each other. EPC Class1/Gen2 (ISO18000-6C) includes support for "dense-interrogator channelized signaling". Dense interrogator channelization signaling, sometimes referred to as "dense reader mode", reduces interference between EPC readers by reducing the likelihood that the reader signal "floods" the tag response signal.
4. The ability to work in the network environment The management of modern logistics realizes the intelligent “seamless†management of the entire process of logistics, which is realized in the network environment. The remote automatic identification system is a combination of information collection points in this network environment, and requires non-contact data collection and exchange for material tracking, vehicle and shelf identification. Combined with computer and communication technology, it can form a cross-regional and cross-industry management network to realize real-time monitoring of raw materials, semi-finished products, finished products, transportation, warehousing, distribution, shelves, final sales, and even return processing. The identification and tracking range of items can be From a small area to the whole country and even the whole world, the automation of the logistics process has been improved, and international circulation has been realized. For this purpose, the reader must have a network interface and the ability to connect directly to the network. The data format of data communication must comply with the requirements of international standards and middleware.
V. Mobile UHF RFID system has become a new hot spot for development. Mobile UHF RFID readers are an important category in RFID readers, and there is a large demand in logistics and supply chain management. Mobile UHF RFID systems include handheld readers, car readers, forklift readers, and cart readers.
Different application areas require mobile readers of different specifications, and such reader technology requirements need to be refined for industrial application needs. For a mobile UHF RFID system, four data are output: the ID of the tag, the DATA of the tag, the immediate location at the time of identification, and the time of identification. The location of the fixed reader is deterministic, but the position of the mobile device is variable and the positioning of the system is an important requirement. The mobile UHF RFID system can be used with common common technologies, such as GPS technology, which is suitable for in-vehicle mobile UHF RFID systems for transportation monitoring. However, the technology may not be suitable for the mobile UHF RFID system for indoor applications. For example, the GPS signal cannot be solved in the warehouse, and the accuracy of the positioning may not meet the management requirements of the accurate location. A better way to locate in the yard or warehouse is to use the ground and shelf positioning labels. This method is low in cost and accurate in location, and can be positioned by the original reader of the mobile device itself.
Secondly, the movable UHF RFID system is not an easy task for the antenna to meet the requirements of electrical characteristics, mechanical installation, structural strength, etc., such as a forklift reader, such as strict restrictions on position and high structural strength requirements. Equipment, many choose microstrip antennas with high strength, small thickness and easy to install.
The third problem with mobile UHF RFID systems is system power, especially handheld RFID readers, which require small size, light weight, easy portability and use, low battery power consumption, and long standby and long working hours. Pay special attention to reduce power consumption during standby, turn off all unnecessary circuits, and learn the power control and management technology of the mobile phone.
The fourth key requirement for a mobile UHF RFID system is data communication under mobile conditions. There are many off-the-shelf solutions in this area, and it is possible to combine mature communication modules into the reader.
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