RFID is an acronym for Radio Frequency Identification. The principle of radio frequency identification technology is non-contact data communication between the reader and the tag to achieve the purpose of identifying the target. The application of radio frequency identification is very wide, typical applications are animal chip, car chip immobilizer, access control, parking lot control, production line automation, material management.
1. Overview of radio frequency identification technology
Radio frequency identification or radio frequency identification technology is a kind of automatic identification technology. It conducts non-contact two-way data communication through radio frequency, and uses radio frequency to read and write recording media (electronic tags or radio frequency cards), so as to achieve identification goals and data. The purpose of exchange, which is considered to be one of the most promising information technologies in the 21st century.
Radio frequency identification technology does not contact fast information exchange and storage technology through radio waves, combines data access technology through wireless communication, and then connects to the database system to achieve non-contact two-way communication, thereby achieving the purpose of identification, for data exchange, A very complex system is connected in series. In the identification system, the reading, writing and communication of electronic tags are realized through electromagnetic waves. According to the communication distance, it can be divided into near field and far field. For this reason, the data exchange method between the read/write device and the electronic tag is correspondingly divided into load modulation and backscatter modulation.
2. The development process of radio frequency identification technology
1940-1950: Due to the development and progress of radar technology, radio frequency identification technology was derived, and the theoretical basis of RFID was born in 1948.
1950-1960: People began to explore RFID technology, but it did not break away from laboratory research.
1960-1970: The relevant theory continues to develop, and the system begins to be used in practice.
1970-1980: RFID technology was continuously updated, product research was gradually deepened, and RFID testing began to be further accelerated. And realized the application to the related system.
1980-1990: RFID technology and related products were developed and applied in the market, and there were various fields of application.
1990-2000: People began to pay attention to the standardization of radio frequency identification, and radio frequency identification systems can be seen in many areas of life.
After 2000: people generally recognized the importance of standardization, the types of radio frequency identification products were further enriched and developed, whether active, passive or semi-active electronic tags began to develop, the related production costs were further reduced, and the application fields gradually increased .
In 2020, RF circuits are integrated circuits that are widely used in wireless communications, ranging from satellite communications to mobile phones, WiFi, and shared bicycles. RF circuits are everywhere. Design is the source of the RF industry chain. RF Electronic Design Automation (EDA) software is the enabler of RF circuit design and an important cornerstone of the RF industry.
The technical theory of RFID has been further enriched and developed. People have developed single-chip electronic tags, multi-electronic tag reading, wireless readable and writable radio frequency identification technology that adapts to high-speed moving objects, and related products have also entered our lives. , and began to be widely used.
3. working principle of radio frequency identification technology
The basic working principle of radio frequency identification technology is not complicated: after the tag enters the reader, it receives the radio frequency signal sent by the reader, and transmits the product information (Passive Tag, passive tag or passive tag) stored in the chip with the energy obtained by the induced current. ), or the tag actively sends a signal of a certain frequency (Active Tag, active tag or active tag), the reader reads and decodes the information, and sends it to the central information system for related data processing.
A complete set of RFID system is composed of three parts: reader and electronic tag, also known as transponder and application software system. Its working principle is that the reader (Reader) emits radio wave energy of a specific frequency for The drive circuit sends the internal data, and the Reader then receives and decodes the data in sequence and sends it to the application for corresponding processing.
In terms of the communication and energy sensing methods between the RFID card reader and the electronic tag, it can be roughly divided into two types: inductive coupling and backscattering coupling. Generally, low-frequency RFID mostly adopts the first method, while higher-frequency RFID mostly adopts the second method.
The reader can be a read or read/write device according to the structure and technology used, and is the information control and processing center of the radio frequency identification system. The reader usually consists of a coupling module, a transceiver module, a control module and an interface unit. Half-duplex communication is generally used to exchange information between the reader and the tag, and the reader provides energy and timing to passive tags through coupling. In practical applications, management functions such as collection, processing and remote transmission of object identification information can be further realized through Ethernet or WLAN.
4. Components of radio frequency identification technology
A complete radio frequency identification system consists of three parts: reader, tag and data management system.
4.1 About the reader
The reader is a device that reads out the information in the tag, or writes the information that the tag needs to store into the tag. Depending on the structure and technology used, the reader can be a read/write device, an radio frequency identification system information control and processing center. When the radio frequency identification system works, the reader transmits radio frequency energy in an area to form an electromagnetic field, and the size of the area depends on the transmission power. The tags in the coverage area of ??the reader are triggered, send the data stored in it, or modify the data stored in it according to the instruction of the reader, and can communicate with the computer network through the interface. The basic composition of the reader usually includes: transceiver antenna, frequency generator, phase-locked loop, modulation circuit, microprocessor, memory, demodulation circuit and peripheral interface.
(1) Transceiver antenna: Send radio frequency signals to the tag, and receive the response signal and tag information returned by the tag.
(2) Frequency generator: generate the operating frequency of the system.
(3) Phase-locked loop: generate the required carrier signal.
(4) Modulation circuit: The signal sent to the tag is loaded into the carrier wave and sent out by the radio frequency circuit.
(5) Microprocessor: generates the signal to be sent to the tag, decodes the signal returned by the tag, and returns the decoded data to the application program. If it is an encrypted system, a decryption operation is required.
(6) Memory: store user programs and data.
(7) Demodulation circuit: demodulate the signal returned by the tag and hand it over to the microprocessor for processing.
(8) Peripheral interface: communicate with the computer.
4.2 About electronic labels
Electronic tags are composed of transceiver antenna, AC/DC circuit, demodulation circuit, logic control circuit, memory and modulation circuit.
(1) Transceiver antenna: Receive the signal from the reader and send the required data back to the reader.
(2) AC/DC circuit: The electromagnetic field energy emitted by the reader is used to provide stable power for other circuits through the output of the voltage stabilizer circuit.
(3) Demodulation circuit: remove the carrier from the received signal and demodulate the original signal.
(4) Logic control circuit: decode the signal from the reader, and send back the signal according to the requirements of the reader.
(5) Memory: a location where the system operates and stores identification data.
(6) Modulation circuit: The data sent by the logic control circuit is loaded into the antenna and sent to the reader after the modulation circuit.
5. Classification of radio frequency identification technology
Radio frequency identification technology can be divided into three categories according to the power supply method of its tags, namely passive RFID, active RFID, and semi-active RFID.
5.1 Passive radio frequency identification
Among the three types of RFID products, passive RFID is the earliest, the most mature, and the most widely used. In passive RFID, the electronic tag completes the information exchange by receiving the microwave signal transmitted by the RFID reader and obtaining energy through the electromagnetic induction coil to supply power to itself for a short time. Because the power supply system is omitted, the volume of passive radio frequency identification products can reach the order of centimeters or even smaller, and its own structure is simple, low cost, low failure rate, and long service life. But as a price, the effective identification distance of passive RFID is usually short, and it is generally used for close contact identification. Passive RFID mainly works in the lower frequency band 125KHz, 13.56MKHz, etc. Its typical applications include: bus cards, second-generation ID cards, canteen meal cards, etc.
5.2 Active radio frequency identification
The rise of active RFID is not long, but it has played an indispensable role in various fields, especially in the electronic non-stop toll collection system of highways. Active RFID is powered by an external power supply and actively sends signals to the RFID reader. Its volume is relatively large. But it also has a longer transmission distance and higher transmission speed. A typical active radio frequency identification tag can establish contact with an RFID reader at a distance of 100 meters, and the read rate can reach 1,700read/sec. Active RFID mainly works in higher frequency bands such as 900MHz, 2.45GHz, and 5.8GHz, and has the function of identifying multiple tags at the same time. The long-distance and high-efficiency of active RFID makes it indispensable in some RFID applications that require high performance and large range.
5.3 Semi-active radio frequency identification
Passive RFID does not supply power by itself, but the effective identification distance is too short. Active RFID has a long enough identification distance, but requires an external power supply and is bulky. And semi-active RFID is a compromise product for this contradiction. Semi-active RFID is also called low frequency activation trigger technology. Under normal circumstances, semi-active radio frequency identification products are in a dormant state and only supply power to the part of the tag that holds the data, so the power consumption is small and can be maintained for a long time. When the tag enters the identification range of the RFID reader, the reader first accurately activates the tag in a small range with a 125KHz low-frequency signal to make it work, and then transmits information to it through 2.4GHz microwave. That is to say, first use low-frequency signals for precise positioning, and then use high-frequency signals to quickly transmit data. Its usual application scenario is: in a large range that a high-frequency signal can cover, multiple low-frequency readers are placed in different positions to activate semi-active RFID products. This not only completes the positioning, but also realizes the collection and transmission of information.
6. Characteristics of radio frequency identification technology
Generally speaking, radio frequency identification technology has the following characteristics:
6.1 Applicability: radio frequency identification technology relies on electromagnetic waves and does not require physical contact between the two parties. This allows it to establish connections regardless of dust, fog, plastic, paper, wood, and various obstacles, and communicate directly.
6.2 Efficiency: The reading and writing speed of the radio frequency identification system is extremely fast, and a typical radio frequency identification transmission process is usually less than 100 milliseconds. High-frequency RFID readers can even identify and read the content of multiple tags at the same time, which greatly improves the efficiency of information transmission.
6.3 Uniqueness: Each RFID tag is unique. Through the one-to-one correspondence between RFID tags and products, the subsequent circulation of each product can be clearly tracked.
6.4 Simplicity: RFID tags have simple structure, high recognition rate and simple reading equipment. Especially as NFC technology is gradually popularized on smartphones, each user's mobile phone will become the simplest RFID reader.
7. Advantages and disadvantages of radio frequency identification technology
7.1 Advantages
Radio frequency identification technology can be widely used in many industries and fields, and it must have its "excellence".
In terms of its external form, the carrier of radio frequency identification technology generally has the characteristics of waterproof, anti-magnetic, high temperature resistance, etc., to ensure the stability of radio frequency identification technology in application. As far as its use is concerned, radio frequency identification has advantages in real-time updating of data, amount of stored information, service life, work efficiency, and security. Radio frequency identification can more conveniently update existing data under the premise of reducing human, material and financial resources, making work more convenient; radio frequency identification technology stores information based on computers, up to several megabytes, and can store a large amount of information , to ensure the smooth progress of the work; the radio frequency identification technology has a long service life, as long as the staff pays attention to protection when using it, it can be reused; the radio frequency identification technology has changed the inconvenience of information processing in the past, and realized the simultaneous use of multiple targets. The identification greatly improves the work efficiency; and the radio frequency identification is also protected by a password, which is not easy to be forged and has high security. The technology similar to the radio frequency identification technology is the traditional bar code technology. The traditional bar code technology is inferior to the radio frequency identification technology in terms of updating data, storing information, service life, work efficiency, security, etc., and cannot be well adapted to our country. The needs of current social development are also difficult to meet the needs of industries and related fields.
7.2 Disadvantages
(1) The technical maturity is not enough. radio frequency identification technology has been around for a short time and is not very mature in technology. Due to the retro-reflective characteristics of UHF radio frequency identification electronic tags, it is difficult to apply them in metals, liquids and other commodities.
(2) High cost. Compared with ordinary barcode labels, the price of radio frequency identification electronic labels is higher than that of ordinary barcode labels.
(3) The security is not strong enough. The security problems faced by radio frequency identification technology are mainly manifested in the illegal reading and malicious tampering of radio frequency identification electronic tag information.
(4) The technical standards are not uniform.
8. Application fields of radio frequency identification technology
8.1 Logistics
Logistics and warehousing is one of the most potential application areas of radio frequency identification. International logistics giants such as UPS, DHL, and Fedex are actively experimenting with radio frequency identification technology, with a view to applying it on a large scale to improve their logistics capabilities in the future. The applicable processes include: cargo tracking in the logistics process, automatic information collection, warehouse management applications, port applications, postal parcels, express delivery, etc.
8.2 Transportation
There have been many successful cases in taxi management, bus hub management, and railway locomotive identification.
8.3 Identification
RFID technology is widely used in personal identification documents because of its fast reading and difficult forgery. Such as the e-passport project, my country's second-generation ID card, student ID and other electronic documents.
8.4 Anti-counterfeiting
RFID has the characteristics of being difficult to counterfeit, but how to apply it to anti-counterfeiting still needs the active promotion of the government and enterprises. The fields of application include the anti-counterfeiting of valuables (tobacco, alcohol, medicine) and the anti-counterfeiting of tickets.
8.5 Asset Management
It can be applied to the management of various assets, including valuables, items with large quantities and high similarity, or dangerous goods. RFID can manage almost all items as tag prices drop.
8.6 Food
It can be applied to the management of fruits, vegetables, fresh food, and food. The application in this field needs to be innovative in the design and application mode of the label.
8.7 Information Statistics
With the use of radio frequency identification technology, information statistics has become a simple and fast job. The query software of the archives information management platform sends out a statistical inventory signal, and the reader quickly reads the data information and related storage location information of the archives, and intelligently returns the acquired information and the information in the central information database for proofreading. For example, for the files that cannot be matched, the administrator will use the reader to carry out on-site verification, adjust the system information and on-site information, and then complete the information statistics work.
8.8 Review the application
When querying the file information, the file manager finds out the file number with the help of the query management platform. The system reads the data in the central information database according to the file number. After verification, the file outbound signal is sent out, and the file is intelligently recognized by the storage location management platform. The function module will combine the file number corresponding to the relevant storage position number to find out the specific part of the file saved. After the administrator transmits the file outbound signal, the indicator light on the storage location lights up immediately. When the data is out of the library, the radio frequency identification reader will feed back the obtained information to the management platform, and the manager will verify it again, and the out-of-the-warehouse file and the checked file will be checked out after checking the same. Moreover, the system will record the information out-of-warehouse time. If the feedback file and the query file do not match, the alarm module in the security management platform will transmit an abnormal warning.
8.9 Security Controls
The security control system can realize the functions of timely monitoring and abnormal alarming of the archives, so as to avoid the destruction and theft of archives. When the archives are borrowed and returned, especially the physical archives, they are often used for exhibition, evaluation and inspection, etc. The manager carefully checks the returned archives and verifies the information before the archives are lent, so as to find out whether the archives are damaged or missing in time.
9. Development trend of radio frequency identification technology
9.1 RFID Tag Trend
With the formulation of standards, the wide range of application fields, the increase in the number of applications, the continuous improvement of technology, and the rapid progress of technology (for example, in the case of books, conductive ink is used to directly print RFID antennas on the cover or copyright pages). The cost will be lower; secondly, the identification distance will be longer, even passive RFID tags can reach tens of meters; the volume will also be smaller.
9.2 High frequency
Compared with the low-frequency system, the UHF radio frequency identification system has the advantages of long identification distance, faster data exchange speed, higher forgery difficulty, stronger anti-interference ability to the outside world, small size, and with the reduction of manufacturing cost and high frequency. With the further improvement of technology, the application of UHF system will be more extensive.
9.3 Networking
In some applications, the data collected by different systems (or multiple readers) need to be processed uniformly and then provided to users. System network management, to achieve remote control and management of the system.
9.4 Pluripotency
With the continuous improvement and popularization of mobile computing technology, the development trend of RFID reader design and manufacture is to develop towards multi-function, multi-interface, multi-standard, and towards modularization, miniaturization, portable and embedded; at the same time, Multi-reader coordination and networking technology will become one of the future development directions.
