1. Brief Introduction of Radio Frequency Identification Technology

Radio Frequency Identification (RFID) is a kind of automatic identification technology. It uses wireless radio frequency to conduct non-contact two-way data communication, and uses wireless radio frequency to read and write recording media (electronic tags or radio frequency cards) to achieve identification objectives and data exchange. It is considered to be one of the most promising information technologies in the 21st century. Radio frequency identification (RFID) technology achieves the purpose of identification by using wireless wave non-contact rapid information exchange and storage technology, combining wireless communication with data access technology, and then connecting to a database system to achieve non-contact two-way communication. It is used for data exchange and concatenates an extremely complex system. In recognition systems, electronic tags are read, written, and communicated through electromagnetic waves. According to the communication distance, it can be divided into near field and far field. Therefore, the data exchange method between read/write devices and electronic tags is also correspondingly divided into load modulation and backscatter modulation.

2. Working principle of RFID technology

The basic working principle of RFID technology is not complex: After a tag enters a reader, it receives the RF signal emitted by the reader, and uses the energy obtained by the induced current to transmit product information stored in the chip (Passive Tag, Passive Tag, or Passive Tag), or the tag actively sends a signal of a certain frequency (Active Tag, Active Tag, or Active Tag). After the reader reads the information and decodes it, Send to the central information system for relevant data processing. A complete RFID system consists of a reader, an electronic tag, or so-called transponder, and an application software system. Its working principle is that the reader emits radio wave energy at a specific frequency, which is used to drive the circuit to send out internal data. At this time, the reader sequentially receives and interprets the data and sends it to the application for corresponding processing. The communication and energy sensing methods between RFID card readers and electronic tags can be roughly divided into two types: inductive coupling and backscatter coupling. Generally, low-frequency RFID mostly uses the first method, while high-frequency RFID mostly uses the second method. The reader can be a read or read/write device depending on the structure and technology used, and it is the information control and processing center of the RFID system. A reader usually consists of a coupling module, a transceiver module, a control module, and an interface unit. Generally, half duplex communication is used between readers and tags for information exchange, while readers provide energy and timing to passive tags through coupling. In practical applications, management functions such as collection, processing, and remote transmission of object recognition information can be further implemented through Ethernet or WLAN.

3. Composition of RFID technology

A complete RFID system consists of three parts: a reader, an electronic tag, and a data management system. (1) About the reader (identification acquisition terminal) The reader is a device that reads out the information in the label or writes the information required to be stored in the label into the label. Depending on the structure and technology used, the reader can be a read/write device, which is the information control and processing center of the RFID system. During the operation of an RFID system, the reader transmits radio frequency energy in an area that forms an electromagnetic field. The size of the area depends on the transmission power. Labels within the reader's coverage area are triggered to send data stored therein, or modify the data stored therein according to the reader's instructions, and can communicate with the computer network through an interface. The basic structure of a reader usually includes a transceiver antenna, frequency generator, phase locked loop, modulation circuit, microprocessor, memory, demodulation circuit, and peripheral interface. A. Transceiver antenna: sends RF signals to the tag and receives the response signal and tag information returned by the tag. B. Frequency Generator: Generates the operating frequency of the system. C. Phase locked loop: generates the required carrier signal. D. Modulation circuit: Load the signal sent to the tag onto the carrier wave and send it out by the RF circuit. E. Microprocessor: Generates the signal to be sent to the tag, decodes the signal returned by the tag, and transmits the decoded data back to the application program. If the system is encrypted, decryption operations are also required. F. Memory: Stores user programs and data. G. Demodulation circuit: Demodulate the signal returned by the tag and submit it to the microprocessor for processing. H. Peripheral interface: communicate with the computer. (2) The electronic tag is composed of a transceiver antenna, an AC/DC circuit, a demodulation circuit, a logic control circuit, a memory, and a modulation circuit. Transceiver antenna: Receives signals from the reader and sends the required data back to the reader. B. AC/DC circuit: Use the electromagnetic field energy emitted by the reader to provide stable power for other circuits through the output of the voltage stabilizing circuit. Demodulation circuit: Remove the carrier wave from the received signal and demodulate the original signal. D. Logic control circuit: Decode the signal from the reader and send back the signal according to the requirements of the reader. E. Memory: The location where the system operates and stores identification data. F. Modulation circuit: The data sent by the logic control circuit is loaded into the antenna and sent to the reader through the modulation circuit.

4. Common types of RFID technology

RFID technology can be divided into three categories based on the power supply method of its tags, namely, passive RFID, active RFID, and semi active RFID. (1) Among the three types of RFID products, passive RFID has the earliest appearance, the most mature, and the most widely used. In passive RFID, electronic tags temporarily power themselves by receiving microwave signals transmitted by RFID readers and obtaining energy through electromagnetic induction coils, thereby completing this information exchange. Because the power supply system is omitted, passive RFID products can have a volume of centimeters or even smaller, and have simple structure, low cost, low failure rate, and long service life. However, as a cost, the effective identification distance of passive RFID is usually shorter, and it is generally used for close contact identification. Passive RFID mainly works in the lower frequency band of 125KHz, 13.56MKHz, and other typical applications include: bus cards, second-generation ID cards, cafeteria meal cards, and so on. (2) Active RFID Active RFID has not emerged for a long time, but it has played an indispensable role in various fields, especially in the electronic toll collection system for highways. Active RFID is powered by an external power source and actively sends signals to the RFID reader. Its volume is relatively large. However, it also has a longer transmission distance and higher transmission speed. A typical active RFID tag can establish contact with a RFID reader from a distance of 100 meters, with a reading rate of 1700 read/sec. Active RFID mainly operates in higher frequency bands such as 900 MHz, 2.45 GHz, and 5.8 GHz, and has the function of identifying multiple tags at the same time. The long-range and efficient nature of active RFID makes it indispensable in some RF identification applications that require high performance and a wide range. (3) Semiactive RFID Passive RFID does not provide power by itself, but the effective identification distance is too short. The active RFID identification distance is long enough, but it requires external power supply and has a large volume. And semi active RFID is the product of compromise for this contradiction. Semiactive RFID is also known as low-frequency activation trigger technology. Under normal circumstances, semi active RFID products are in a dormant state and only supply power to the portion of the tag that holds data. Therefore, they consume less power and can be maintained for a longer time. After 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 into a working state, and then transmits information to it through a 2.4GHz microwave. That is, first use low-frequency signals to accurately locate, and then use high-frequency signals to quickly transmit data. Its typical application scenario is to place multiple low-frequency readers at different locations in a large range that can be covered by a high-frequency signal to activate a semi-active RFID product. This not only completes the positioning, but also realizes the collection and transmission of information.

5. Application field of RFID technology

(1) Intelligent logistics application Logistics warehousing is one of the most potential applications of RFID. International logistics giants such as UPS, DHL, and Fedex are actively experimenting with RFID technology, with a view to large-scale application in the future to improve their logistics capabilities. The applicable processes include: cargo tracking in the logistics process, automatic information collection, warehouse management applications, port applications, postal parcels, express delivery, etc. (2) There have been many successful cases of intelligent transportation applications such as taxi management, bus hub management, and railway locomotive identification. (3) RFID technology is widely used in personal identification documents due to its fast reading and difficulty in counterfeiting. Such as the electronic passport project, China's second generation identity cards, student cards, and other electronic documents. (4) The anti-counterfeiting identification application RFID has the characteristics of being difficult to forge, but how to apply it to anti-counterfeiting still requires the active promotion of the government and enterprises. The fields that can be applied include the anti-counterfeiting of valuables (cigarettes, alcohol, drugs) and the anti-counterfeiting of tickets. (5) Asset management applications can be applied to the management of various types of assets, including valuables, large quantities of highly similar items, or dangerous goods. With the decrease in tag prices, RFID can manage almost all items. (6) Food management applications can be applied to the management of fruits, vegetables, fresh food, food, etc. Application in this field requires innovation in the design and application mode of labels. (7) With the application of RFID technology, information statistics has become a simple and fast task. The query software of the archives information management platform sends out statistical inventory signals, and the reader quickly reads the data information and relevant storage location information of the archives in the library, and intelligently returns the obtained information and the information in the central information database for proofreading. For example, for files that cannot be matched, the manager uses a reader to conduct on-site verification, adjust system information and on-site information, and then complete information statistics. (8) When querying file information, the file manager uses the query management platform to find the file number. The system reads the data from the central information base according to the file number, and after verification, sends out a file outbound signal. The intelligent file identification function module of the storage location management platform will identify the specific location where the file is stored based on the file number corresponding to the relevant storage location number. After the manager sends out the file outbound signal, the indicator light on the storage site immediately lights up. When the data is warehoused, the RFID reader will feed back the obtained information to the management platform, and the manager will verify it again. After verifying that the warehoused file and the checked file are the same, the data will be warehoused. Moreover, the system will record the time when the information was sent out of the warehouse. If the feedback file and the query file do not match, the alert module within the security management platform will transmit an exception alert. (9) Security Control Application The security control system can achieve functions such as timely monitoring and abnormal alarm of archives to avoid destruction and theft of archives. When files are borrowed and returned, especially physical files, they are often used for exhibition, evaluation, and inspection. Managers carefully inspect the returned files and verify with the information before the files were lent, so as to promptly detect whether the files are damaged or missing.

6. Development Trend of Radio Frequency Identification Technology

With the formulation of standards, the wide range of applications, the increase in the number of applications, the continuous improvement of processes, and the rapid progress of technology (for example, in books, using conductive ink directly on the cover or copyright page to print RFID antennas), the cost will be lower; Secondly, the recognition distance is further, even for passive RFID tags, it can reach tens of meters; The volume will also be smaller. (1) Compared with low-frequency systems, high-frequency UHF RFID systems have the advantages of long recognition distances, faster data exchange speed, higher forgery difficulty, stronger anti-interference ability to the outside world, and small size. Moreover, with the reduction of manufacturing costs and the further improvement of high-frequency technology, the application of UHF systems will be more widespread. (2) In some networked applications, it is necessary to uniformly process the data collected by different systems (or multiple readers) and provide them to users for use. For example, if we use a second-generation ID card to collect train tickets from an automatic ticket collector, this requires networked management of the RFID system to achieve remote control and management of the system. (3) With the continuous improvement and popularization of mobile computing technology, the development trend of RFID reader design and manufacturing will be towards multi-function, multiple interfaces, multiple formats, and towards modularization, miniaturization, portability, and embedded; At the same time, multi reader coordination and networking technology will become one of the future development directions.

7. NFC Near Range Communication Technology

The full Chinese name for NFC is Near Field Communication Technology. NFC is developed on the basis of non-contact radio frequency identification (RFID) technology combined with wireless interconnection technology. It provides a very safe and fast communication method for various electronic products that are increasingly popular in our daily life. "Near field" in the Chinese name of NFC refers to radio waves that are adjacent to electromagnetic fields. Because radio waves are actually electromagnetic waves, they follow the Maxwell equation. Electric and magnetic fields undergo alternating energy conversion during the process of propagating from the transmitting antenna to the receiving antenna, and enhance each other during the conversion. For example, the radio signals used in our mobile phones are propagated using this principle, which is called far field communication. Within 10 wavelengths of an electromagnetic wave, the electric field and magnetic field are independent of each other. At this time, the electric field has little significance, but magnetic fields can be used for short distance communication, which we call near-field communication. The near-field communication service combines near-field communication technology and mobile communication technology, achieving multiple functions such as electronic payment, identity authentication, ticketing, data exchange, anti-counterfeiting, advertising, and so on. It is a new type of service in the field of mobile communication. Near field communication services have enhanced the functionality of mobile phones, enabling users to gradually move towards electronic consumption behavior, and establishing a new type of user consumption and business model. The application of NFC technology has received widespread attention worldwide, with different roles such as telecom operators and mobile phone manufacturers at home and abroad launching application trials. Some international associations and organizations are also actively engaged in standardization development. According to the prediction of relevant institutions in the industry, mobile applications based on near-field communication technology will become the next killer application of mobile value-added services.

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