What are RFID tags? What are the applications of this technology?

Radio frequency identification (RFID) technology uses electromagnetic fields to automatically identify and track tags attached to objects. Near field communication (NFC) is a standard based on short-range RFID high-frequency technology that supports a frequency of 13.56 MHz.

NFC technology is widely used in today's products, the most common of which is electronic payment systems, such as contactless card payments and e-wallets. The EMV™ contactless payment standard provides a fast and secure transaction method close to NFC payment devices.

RFID Technology Overview

RFID technology is an automatic identification technology that does not require direct contact with the target. It is also called a contactless IC card or ID tag. It can detect and identify specific targets. RFID technology was first used in the 1980s and was initially limited to maritime transportation, traffic information systems and other special applications. Over time, RFID technology has gradually become miniaturized and widely used. At present, some standards have emerged to define RFID frequencies, communication methods and purposes.

What is RFID technology?

RFID is the abbreviation of Radio Frequency Identification, which is the specific application and development of automatic identification technology in radio technology. The basic idea of this technology is to automatically identify the target object and obtain relevant data by using radio frequency signals, without human 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.

Simplified RFID system

The RFID system model is shown in the figure above. The loop antenna in the RFID Reader/recorder communicates with the loop antenna in the RFID tag through electromagnetic coupling. The RFID reader/recorder outputs the radio frequency signal, and the RFID tag receives the signal through the loop antenna. The detector circuit of the integrated circuit (IC chip) in the RFID tag detects the radio frequency signal and obtains energy to drive the IC chip to work.

Data communication between the RFID reader/recorder and the RFID tag generally uses 13.56 MHz ASK modulation.

Evaluating RFID tags

The manufacturing process of RFID tags

The figure above shows a typical card-type RFID tag manufacturing process.

First, a loop antenna is formed on the card by printing or other means, and then the IC chip and chip capacitor are placed on the same card. The capacitor can also be made by printing. Finally, the tag is packaged, tested and shipped.

Complete RFID Circuit Diagram

The figure above shows a complete RFID circuit diagram.

Typically, an RFID tag consists of an L-C-R parallel circuit, where "L" represents the loop antenna, "C" represents the chip capacitor, and "R" represents the IC chip. The resonant frequency f0 of the RFID tag can be calculated by the formula 1/(2π√LC). If the resonant frequency of the RFID tag is close to 13.56 MHz, it means that the tag can communicate well with the RFID reader/writer. It is very important to verify that the resonant frequency of the entire tag is 13.56 MHz. At the same time, verifying the characteristics of the L and C components also helps to improve the production efficiency of RFID tags.

Another factor to consider is the sharpness of the resonance curve (communication bandwidth), which depends on the R value of the IC chip or the parasitic resistance R value of the loop antenna.

When the modulation signal bandwidth is too wide, the sharpness of the resonance curve is too high, which will cause communication difficulties; when the sharpness of the resonance curve is too low, it will cause the communication distance characteristics to deteriorate. Therefore, the resonance characteristics of the entire tag must be measured comprehensively, and the resistance value must be measured step by step to help improve the communication performance of the RFID tag.

RFID technology application cases

1. Military logistics system RFID

The application of RFID technology in military logistics systems originated in the United States. As early as World War II, it was used for aircraft enemy identification. In recent years, in local wars, RFID technology has been successfully applied to the Logistics Management of US military logistics. Whether it is in the ordering of materials, transportation or storage in warehouses, through the RFID system, commanders at all levels can grasp all logistics information in real time. RFID receiving and sending devices are usually installed at key nodes such as transportation line checkpoints, warehouses, stations, docks, airports, etc. After receiving the RFID tag information, the receiving device transmits it to the logistics dispatch management center together with the location information of the receiving location, and Stores it in the center's information database.

As an automatic identification system, RFID technology can automatically identify targets and collect data through non-contact radio frequency signals. It can identify high-speed moving targets and multiple targets at the same time without human intervention. It is quick and convenient to operate and can adapt to various harsh environments. Regardless of the procurement, transportation, storage, use or maintenance of military supplies, commanders at all levels can grasp their information and status in real time. RFID can collect and exchange data between RFID readers and RFID electronic tags at a very fast speed. It has the ability of intelligent reading and writing and encrypted communication, the world's unique password, and strong information confidentiality, which provides an accurate, fast, safe and controllable technical approach for military logistics systems. Therefore, it is very urgent and necessary to vigorously promote the application of RFID technology in military logistics systems.

2. Access Control security

The future access control security system will widely use radio frequency card technology. A radio frequency card can have multiple functions, such as work permits, access permits, parking cards, hotel accommodation cards and even travel pasSports. Its purpose is to identify personnel identities, conduct security management and charge fees. The application of radio frequency cards can simplify entry and exit procedures, improve work efficiency and provide security protection. As long as the personnel wear the radio frequency card packaged in the size of an ID Card and install the RFID reader at the entrance and exit, the system can automatically identify the personnel and alarm for illegal intrusion. In places with high security requirements, fingerprints, palm prints or facial features can be stored in the radio frequency card in combination with other identification methods.

In addition, companies can also use radio frequency cards to protect and track property, and attach radio frequency cards to items such as computers, fax machines, documents, copiers or other laboratory supplies. By using radio frequency cards, companies can automatically track and manage these valuable properties, track the departure of items from a certain place, or restrict items from leaving a certain area through an alarm system. In addition, combined with the GPS system, radio frequency cards can also be used to effectively track container trucks, cargo holds, etc.

The application of radio frequency cards in access control security systems can simplify procedures, improve work efficiency, and provide security protection. In addition, radio frequency cards can also be used to protect and track property, provide automatic management and tracking functions, and improve property security.

3. Car anti-theft

In car anti-theft systems, RFID technology is a relatively new application. Now, small enough radio frequency cards have been developed that can be encapsulated into car keys and have specific code words. RFID readers are installed in cars. When the key is inserted into the ignition, the RFID reader can identify the key. If the RFID reader cannot receive the specific signal sent by the radio frequency card, the car engine will not start. Through this electronic verification method, the car's central computer can effectively prevent short-circuit ignition and other situations.

Another car anti-theft system is that the driver carries a radio frequency card with a transmission range limited to 45~55cm from the driver's seat, and the RFID reader is installed on the back of the seat. When the RFID reader reads a valid ID number, the system will emit three beeps before the car engine can be started. This anti-theft system also has another powerful function: if the driver leaves the car with the door open and the engine is not turned off, the RFID reader needs to read another valid ID number; if the driver takes the radio frequency card away from the car, the RFID reader cannot read the valid ID number, the engine will automatically shut down and trigger the alarm device.

4. Electronic Article Monitoring System

The electronic article monitoring system is designed to prevent the theft of goods. The system consists of a radio frequency card and an RFID reader at the store exit. The radio frequency card is activated when installed. Once the radio frequency card is in an activated state and close to the scanner, the system will detect and trigger an alarm. When the goods are purchased, the salesperson will use a special Tool to remove the radio frequency card (more common in clothing stores), or disable the radio frequency card through a magnetic field, or directly destroy the electrical characteristics of the radio frequency card.

The electronic article monitoring system effectively prevents the theft of goods through the cooperation of radio frequency cards and RFID readers. Once the radio frequency card is activated and leaves the store without checking out, the system will sound an alarm to alert the clerk and security personnel. This system is widely used in the Retail Industry to protect the safety of goods and improve the safety of stores.

Working Principle of RFID

RFID system usually consists of three main components: RFID tag (also called transponder), RFID reader (also called transceiver) and RFID Antenna. RFID tag is used to provide tracking data of the target, RFID reader is used to collect RFID tag information and transmit it to the network for tracking, and antenna enables RFID reader to read RFID tag data. In the process of developing RFID system, there are also some challenges, including interoperability of components and technical issues related to the end-use environment, such as the proximity of the identification target to the RFID reader, the length of time the target needs to be tracked, the wireless regulations of the country or region, and environmental conditions that may affect the system, such as temperature and humidity.

1. Electronic tag (radio frequency card)

Usually composed of chip and coupling components, the chip is equipped with EEPROM for storing identification code or other data, and the tag contains a built-in antenna. Its main function is to communicate with the RFID reader. Compared with the same or early identification technologies such as barcode, magnetic card, IC card, etc., radio frequency card has the advantages of non-contact, long working distance, adaptability to harsh environment, and ability to identify moving targets.

According to the different energy supply methods, RFID tags can be divided into passive tags, semi-active tags and active tags. Among them, the chip energy in semi-active tags and active tags is provided by the battery attached to the RFID electronic tag, and the active tag can actively send out radio frequency signals. According to the different working frequencies, RFID tags can be divided into different types such as low frequency (LF), high frequency (HF), ultra-high frequency (UHF) and microwave. The working principles of RFID in different frequency bands are also different. RFID electronic tags in low frequency and high frequency bands usually adopt the principle of electromagnetic coupling, while RFID in UHF and microwave bands usually adopt the principle of electromagnetic emission.

2. RFID reader: A device that reads tag information

The main task of the RFID reader is to control the radio frequency module to transmit a read signal to the RFID tag and receive the tag's response. The RFID reader will decode the object identification information of the RFID tag and transmit the object identification information together with other relevant information on the tag to the host for processing.

In most RFID systems, the RFID reader will emit electromagnetic waves in an area (the size of the area depends on the working frequency and the size of the antenna). There is an LC series resonant circuit inside the radio frequency card, and its frequency is the same as the frequency emitted by the RFID reader. When the RFID Card passes through this area, the LC resonant circuit resonates under the excitation of electromagnetic waves, causing the capacitor to accumulate charge. At the other end of the capacitor, there is a unidirectional electronic pump that transfers the charge in the capacitor to another capacitor for storage. When the accumulated charge reaches 2V, the capacitor can be used as a power supply to provide working voltage for other circuits, send the data in the card or receive the data from the reader. After receiving the data from the card, the reader will decode and error check to determine the validity of the data, and then transmit the data to the computer network via RS232, RS422, RS485 or wirelessly. Simple RFID products can be regarded as a contactless IC card, while complex RFID products can be connected to external sensor interfaces to measure and record different parameters, and can even be connected to GPS systems to track objects.

3. Antenna

Antenna is a device that can receive or radiate the power of radio frequency signals from a radio transceiver, and it works in the form of electromagnetic waves. According to different working frequency bands, antennas can be divided into long wave, short wave, ultra short wave and microwave antennas, etc. According to different directivities, antennas can be divided into omnidirectional antennas, directional antennas, etc. According to different shapes, antennas can be divided into linear antennas, planar antennas, etc.

In RFID systems, antennas are divided into tag antennas and reader antennas. The current RFID system is mainly concentrated in LF, HF (13.56MHz), UHF and microwave bands. In LF and HF bands, since there is no electromagnetic wave propagation in the near field of the system, the design and working principle of the antenna are fundamentally different from those in UHF and microwave bands.

The reader sends a radio frequency signal of a specific frequency through the transmitting antenna. When the radio frequency card enters the working area of the transmitting antenna, an induced current is generated, thereby activating the radio frequency card. The radio frequency card sends its own encoding and other information through the built-in transmitting antenna. The system's receiving antenna receives the carrier signal sent by the radio frequency card and transmits it to the reader through the antenna regulator. The reader demodulates and decodes the received signal, and then sends it to the background main system for relevant processing. The main system determines the legitimacy of the card based on logical operations, and makes corresponding processing and control according to the settings, and sends out command signals to control the action of the actuator.