Compared with the traditional magnetic card and IC card technology, the radio frequency identification (RFID) technology has the characteristics of non-contact, fast reading speed, and non-wearing. It has developed rapidly in recent years. In order to strengthen Chinese engineers' understanding of the technology, this article introduces the working principle, classification, standards and related applications of RFID technology in detail.
RFID technology uses wireless radio frequency to carry out non-contact two-way data transmission between the reader and the radio frequency card to achieve the purpose of target identification and data exchange. Compared with the traditional barcode, magnetic card and IC card, the radio frequency card has the characteristics of non-contact, fast reading speed, no wear, no environmental influence, long life, easy to use and anti-collision function, which can handle multiple cards at the same time. card. In foreign countries, radio frequency identification technology has been widely used in many fields such as industrial automation, commercial automation, and transportation control management.
System composition and working principle
The most basic RFID system consists of three parts:
1. Tag (Tag, RF card): It is composed of coupling elements and chips. The tag contains a built-in antenna for communication with the RF antenna.
2. Reader: a device that reads (can also write in the card reader) tag information.
3. Antenna: transmit radio frequency signal between tag and reader.
Some systems are also connected to an external computer (host computer system) through the RS232 or RS485 interface of the reader for data exchange.
The basic working process of the system is: the reader sends a certain frequency radio frequency signal through the transmitting antenna. When the radio frequency card enters the working area of the transmitting antenna, an induced current is generated, and the radio frequency card gains energy and is activated; the radio frequency card sends its own encoding and other information through the built-in card The antenna is sent out; the system receiving antenna receives the carrier signal sent from the radio frequency card, and transmits it to the reader through the antenna adjuster. The reader demodulates and decodes the received signal and then sends it to the background main system for related processing; the main system Judging the validity of the card according to logic operations, making corresponding processing and control for different settings, and issuing command signals to control the actions of the actuators.
In terms of coupling method (inductance-electromagnetic), communication process (FDX, HDX, SEQ), data transmission method from radio frequency card to reader (load modulation, backscatter, high-order harmonics), and frequency range, there are different There are fundamental differences in non-contact transmission methods, but all readers are very similar in functional principles and the design and construction determined thereby. All readers can be simplified into two basic modules, high-frequency interface and control unit. The high-frequency interface includes a transmitter and a receiver. Its functions include: generating high-frequency transmission power to activate the radio frequency card and provide energy; modulating the transmitted signal to transmit data to the radio frequency card; receiving and demodulating the data from the radio frequency card High frequency signal. The high-frequency interface design of different radio frequency identification systems has some differences. The schematic diagram of the high-frequency interface of the inductive coupling system is shown in Figure 1.
The functions of the control unit of the reader include: communicating with the application system software and executing commands sent by the application system software; controlling the communication process with the radio frequency card (master-slave principle); signal encoding and decoding. For some special systems, there are additional functions such as implementing anti-collision algorithms, encrypting and decrypting the data to be transmitted between the radio frequency card and the reader, and performing identity verification between the radio frequency card and the reader.
The read-write distance of the radio frequency identification system is a very critical parameter. At present, the price of long-distance radio frequency identification system is still very expensive, so it is very important to find a way to increase its reading and writing distance. The factors that affect the reading and writing distance of the RF card include the operating frequency of the antenna, the RF output power of the reader, the receiving sensitivity of the reader, the power consumption of the RF card, the Q value of the antenna and the resonant circuit, the antenna direction, and the coupling of the reader and the RF card Degree, as well as the energy obtained by the radio frequency card itself and the energy for sending information. The reading distance and writing distance of most systems are different, and the writing distance is about 40% to 80% of the reading distance.
Standards and classifications of radio frequency cards
At present, many companies that produce RFID products adopt their own standards, and there is no uniform standard in the world. Currently, several standards available for radio frequency cards are ISO10536, ISO14443, ISO15693 and ISO18OOO. The most widely used are ISO14443 and ISO15693, both of which are composed of four parts: physical characteristics, radio frequency power and signal interface, initialization and anti-collision, and transmission protocol.
According to different methods, radio frequency cards are classified into the following categories:
1. According to the power supply mode, it is divided into active cards and passive cards. Active means that there is a battery in the card to provide power, which has a long operating distance, but has a limited lifespan, large size, high cost, and is not suitable for working in harsh environments; there is no battery in the passive card, and it uses beam power technology to The received radio frequency energy is converted into a DC power supply to supply power to the circuit in the card. Its operating distance is shorter than that of an active card, but it has a long life and does not require high working environment.
2. According to the carrier frequency, it is divided into low frequency radio frequency card, intermediate frequency radio frequency card and high frequency radio frequency card. There are mainly 125kHz and 134.2kHz low-frequency radio frequency cards, the main frequency of the intermediate frequency radio frequency card is 13.56MHz, and the main high-frequency radio frequency card is 433MHz, 915MHz, 2.45GHz, 5.8GHz, etc. Low-frequency systems are mainly used in short-distance, low-cost applications, such as most access control, campus cards, animal supervision, cargo tracking, etc. The intermediate frequency system is used for access control and application systems that need to transmit a large amount of data; the high frequency system is used in occasions that require a long read and write distance and high read and write speed, and its antenna beam direction is narrow and the price is higher. Application in highway toll collection and other systems.
3. According to different modulation methods, it can be divided into active and passive. The active radio frequency card uses its own radio frequency energy to actively send data to the reader; the passive radio frequency card uses the modulated scattering method to transmit data, and it must use the carrier of the reader to modulate its own signal. This type of technology is suitable for access control or In transportation applications, because the reader can ensure that only radio frequency cards within a certain range are activated. In the case of obstacles, using the modulated scattering method, the energy of the reader must come and go through the obstacle twice. The signal transmitted by the active radio frequency card passes through the obstacle only once, so the active radio frequency card is mainly used in applications with obstacles and has a longer distance (up to 30 meters).
4. According to the working distance, it can be divided into close coupling card (working distance less than 1 cm), close coupling card (working distance less than 15 cm), loose coupling card (working distance about 1 meter) and long-distance card (working distance from 1 meter) To 10 meters or even farther).
5. According to the chip, it is divided into read-only card, read-write card and CPU card.
Radio frequency technology
Compared with traditional magnetic card and IC card technology, radio frequency technology (RFID) has the characteristics of non-contact, fast reading speed, and non-wearing. It has developed rapidly in recent years. In order to strengthen Chinese engineers' understanding of this technology, this article introduces the working principle, classification, standards and related applications of radio frequency technology in detail.
Radio frequency technology uses wireless radio frequency to carry out non-contact two-way data transmission between the reader and the radio frequency card to achieve the purpose of target identification and data exchange. Compared with the traditional barcode, magnetic card and IC card, the radio frequency card has the characteristics of non-contact, fast reading speed, no wear, no environmental influence, long life, easy to use and anti-collision function, which can handle multiple cards at the same time. card. In foreign countries, radio frequency identification technology has been widely used in many fields such as industrial automation, commercial automation, and transportation control management.
The basic working process of the radio frequency technology system is: the reader sends a radio frequency signal of a certain frequency through the transmitting antenna, and when the radio frequency card enters the working area of the transmitting antenna, an induced current is generated, and the radio frequency card gains energy and is activated; the radio frequency card passes its own encoding and other information through the card The built-in transmitting antenna sends it out; the system receiving antenna receives the carrier signal sent from the radio frequency card, and transmits it to the reader via the antenna adjuster. The reader demodulates and decodes the received signal and then sends it to the background main system for related processing; The main system judges the legitimacy of the card according to the logic operation, makes corresponding processing and control for different settings, and sends out instruction signals to control the action of the actuator.
In terms of coupling method (inductance-electromagnetic), communication process (FDX, HDX, SEQ), data transmission method from radio frequency card to reader (load modulation, backscatter, high-order harmonics), and frequency range, there are different There are fundamental differences in non-contact transmission methods, but all readers are very similar in functional principles and the design and construction determined thereby. All readers can be simplified into two basic modules, high-frequency interface and control unit. The high-frequency interface includes a transmitter and a receiver. Its functions include: generating high-frequency transmission power to activate the radio frequency card and provide energy; modulating the transmitted signal to transmit data to the radio frequency card; receiving and demodulating the data from the radio frequency card High frequency signal. There are some differences in the high-frequency interface design of different RFID systems.
The functions of the control unit of the reader include: communicating with the application system software and executing commands sent by the application system software; controlling the communication process with the radio frequency card (master-slave principle); signal encoding and decoding. For some special systems, there are additional functions such as implementing anti-collision algorithms, encrypting and decrypting the data to be transmitted between the radio frequency card and the reader, and performing identity verification between the radio frequency card and the reader.
The read-write distance of the radio frequency technology identification system is a very critical parameter. At present, the price of long-distance radio frequency identification system is still very expensive, so it is very important to find a way to increase its reading and writing distance. The factors that affect the reading and writing distance of the radio frequency card include the working frequency of the antenna, the RF output power of the reader, the receiving sensitivity of the reader, the power consumption of the radio frequency card, the Q value of the antenna and the resonant circuit, the antenna direction, the coupling of the reader and the radio frequency card Degree, as well as the energy obtained by the radio frequency card itself and the energy for sending information. The reading distance and writing distance of most systems are different, and the writing distance is about 40% to 80% of the reading distance.
Since the 1990s, radio frequency identification technology has developed rapidly all over the world. The global total sales are growing rapidly at an average annual rate of more than 25%. After more than ten years of development, radio frequency identification technology has been widely used in all walks of life, especially in the electronic information industry.
The application of radio frequency identification technology in my country should still be in its infancy. The gap is first manifested in technology. Although there is a certain foundation in the application of low-frequency and intermediate-frequency products, there are basically no large-scale mature application cases in the high-frequency field; secondly, in the application environment, electronic tags are a kind of Tools to improve the efficiency and accuracy of recognition. The higher the degree of marketization, the more competitive and the stronger the organization's requirements for efficiency. In this case, electronic tags will have the possibility of wide application. Taking the application of electronic tags in the supply chain as an example, it must be based on the mature and extensive use of the supply chain. However, the development of my country's supply chain has just had a good start. For most companies, this kind of advanced Management methods and technologies are still in their infancy.
The localization of radio frequency technology is urgent. No matter from which aspect, if we only rely on imported products from abroad for a long time, it will hinder the promotion and large-scale use of radio frequency technology. On the road to the localization of radio frequency, the localization of the application system started first, and it has been relatively effective at present. With the gradual maturity of system application technology and the growth of the market, many excellent system integrators have emerged, especially in the application of medium and low frequency non-contact products.
The localization of electronic tags can be divided into three aspects: chip technology, module packaging and label processing. At present, a relatively mature IC card module package has been formed in China. Some domestic enterprises have made new attempts in the packaging of electronic tags, which has promoted the further reduction of the cost of electronic tags. The other is the localization of readers and peripherals. In fact, the localization of machinery and peripheral equipment is a key factor in the promotion of electronic labels. Only by truly digesting the existing foreign advanced technology can its products have real market competitiveness and long-term vitality.
In the long run, the market for electronic tags, especially high-frequency and long-distance electronic tags, will gradually mature in the next few years and become another market with broad market prospects and huge capacity in the IC card field after buses, mobile phones, and ID cards. It will be a major industry opportunity for the IC card industry, which is relatively familiar in China. In the face of this industry opportunity, domestic manufacturers should increase investment, take precautions, and achieve technological breakthroughs. In addition, in addition to the efforts of manufacturers, the competent government departments should also play a guiding and leading role, support domestic manufacturers, formulate industry standards according to domestic needs, start with standards, establish an entire system of independent intellectual property rights, and further shorten and The gap in the domestic advanced level has strengthened the development of the domestic smart card industry. Fudan Microelectronics will be committed to the development and promotion of non-contact electronic label technology for a long time. While providing customers with products that meet their needs, it will also provide other manufacturers of the entire product with all-round technical support related to the application of RFID radio frequency identification.
Since 2004, there has been an upsurge of radio frequency identification technology (RFID) worldwide. Commercial giants including Wal-Mart, Procter & Gamble, and Boeing have all actively promoted the application of RFID in manufacturing, logistics, retail, transportation and other industries. . RFID technology and its application are in a period of rapid rise. It is recognized by the industry as one of the most potential technologies of this century. Its development and application promotion will be a technological revolution in the automatic identification industry. The application of RFID in the transportation and logistics industry provides a new stage for communication technology and will become one of the potential profit growth points of the telecommunications industry in the future.
RFID technology can complete information input and processing without direct contact, without optical visibility, without manual intervention, and is convenient and quick to operate. It can be widely used in production, logistics, transportation, transportation, medical treatment, anti-counterfeiting, tracking, equipment and asset management, etc. Need to collect and process data
1. Principles of Radio Frequency Technology
The basic principle of radio frequency technology RF (Radio Frequency) is electromagnetic theory. The advantage of the radio frequency system is that it is not limited to the line of sight, and the recognition distance is farther than the optical system. The radio frequency identification card can read and write, can carry a large amount of data, is difficult to forge, and is intelligent.
In recent years, the application of portable data terminal (PDT) has increased. PDT can store or transfer the collected useful data to a management information system. A portable data terminal generally includes a scanner, a small but powerful computer with memory, a display, and a keyboard for manual input. A permanent memory operating system is installed in the read-only memory to control the collection and transmission of data.
The data in the PDT memory can be transmitted to the host computer through radio frequency communication technology at any time. Scan the location label during operation, and input the shelf number and product quantity into the PDT, and then transmit these data to the computer management system through RF technology. You can get the customer's product list, invoice, shipping label, product code and quantity stored in the place, etc. .
2. Applicability of radio frequency technology in logistics management
RF is suitable for occasions that require non-contact data collection and exchange, such as material tracking, vehicle and shelf identification. Due to the readable and writable ability of RF tags, it is especially suitable for occasions where data content needs to be changed frequently.
The application of RF in my country has also begun. Some expressway toll gates can use RF to charge without stopping. The trial of using RF to record freight car numbers in my country's railway system has been running for some time. Some logistics companies are also preparing to use RF for logistics. Under management.
3. Application of Radio Frequency Technology in Military Logistics
The United States and the North Atlantic Treaty Organization (NATO) in Bosnia’s "joint operations" not only built the most complex communications network in the history of war, but also perfected a new logistics system for identifying and tracking military supplies. This is what we learned." The lesson of repeated transportation caused by the inability to track a large number of materials during the Desert Storm military operation. Regardless of whether the materials are being ordered, transported, or stored in a warehouse, through this system, commanders at all levels can grasp all the information in real time . The function of the transportation part of the system is realized by the radio frequency identification tags attached to the containers and equipment. RF receiving and forwarding devices are usually installed at some checkpoints of transportation lines (such as gate posts, beside bridge piers, etc.), as well as key locations such as warehouses, stations, docks, and airports. After the receiving device receives the RF tag information, it connects to the location information of the receiving place, uploads it to the communication satellite, and then transmits it to the transportation dispatch center by the satellite, and sends it to the central information database.
Our other product:
