What is an RFID Tag? Introduction to Working Principles and Application Scenarios

Basic Concepts and Development History of RFID Tags

RFID (Radio Frequency Identification) is a non-contact automatic identification technology. It exchanges data between readers and tags through radio frequency signals without physical contact or visual alignment. A typical RFID system consists of three components: tags, readers, and back-end data processing systems.

The origin of RFID technology can be traced back to World War II. The British military used Identification Friend or Foe (IFF) systems to distinguish friendly aircraft from enemy aircraft. This principle laid the foundation for radio frequency identification. In the 1970s, RFID technology began commercial applications. From animal identification to access control management, and today's supply chain automation, RFID has undergone decades of technological iteration. Since the 21st century, advances in chip manufacturing and printed antenna technology have continuously reduced the cost of RFID tags. Large-scale deployment of UHF RFID in logistics and retail has become a reality.

Today, radio frequency identification technology covers multiple industries. Fashion retail giant Uniqlo has achieved full-store RFID coverage. The premium liquor industry uses RFID for anti-counterfeiting and traceability. Behind every electronic tag lies a complete data acquisition system.

How RFID Works: Electromagnetic Coupling and Data Communication

RFID operation depends on the radio frequency signals emitted by the reader. Passive tags do not have built-in batteries. They receive electromagnetic energy from the reader through the antenna and use induced current to activate the chip. After activation, the chip modulates stored data and reflects it back to the reader. This process is called backscatter.

The reader is responsible for transmitting RF signals, receiving data returned by tags, and exchanging information with back-end systems. The back-end system performs further processing and business logic judgment on the data. The three components work together to complete a contactless data read. The entire identification process is typically completed within tens of milliseconds without human intervention.

A reader can identify hundreds of tags simultaneously within a beam range. This is the most essential difference between RFID and barcode scanning. Barcodes require individual alignment and scanning, while RFID supports batch reading.

Internal Structure of RFID Tags

A typical RFID adhesive label consists of three core components: chip, antenna, and substrate.

The chip is the brain of the tag, responsible for storing and processing data. Common RFID chip suppliers include NXP, Impinj, and Alien. The chip contains memory units and control logic. It determines the tag's protocol standard, storage capacity, and operating frequency.

The antenna serves as the energy entry point and signal channel for the tag. The antenna of a passive tag is responsible for both receiving RF energy from the reader and backscattering data. The shape and size of the antenna directly affect reading distance and performance. UHF RFID antennas are typically dipole or meander structures, printed on the substrate.

The substrate is the physical support layer that carries the chip and antenna. Common materials include PET film, paper, or PVC. The substrate is ultimately processed into adhesive labels and attached to products or packaging surfaces.

Frequency Classification of RFID

RFID tags are divided into three major categories by operating frequency. Frequency determines reading distance, transmission speed, and environmental adaptability.

Low Frequency (LF, 125-134kHz)

LF RFID was the earliest commercialized frequency band. Reading distance ranges from 0.1 meters to 1 meter. It has strong penetration and is less affected by metal and liquids. Mainly used for animal implantation chips, vehicle access control, and tool tracking. LF technology is mature, but data transmission speed is slow and not suitable for fast identification logistics scenarios.

High Frequency (HF, 13.56MHz) and NFC

HF RFID has a reading distance of approximately 0.1 meters to 1 meter. Transmission speed is higher than LF. The HF standard ISO 15693 is used for library management and access control. The 13.56MHz frequency band also carries NFC (Near Field Communication) technology. NFC is a subset of HF RFID. It operates at 13.56MHz with a reading distance of about 4-10 centimeters. Applications cover mobile payments, electronic ticketing, and product anti-counterfeiting verification.

The advantage of NFC is that smartphones have fully integrated it. Consumers can bring their phone close to a tag to read information. This makes NFC an ideal entry point for brand-consumer interaction.

Ultra-High Frequency (UHF, 860-960MHz)

UHF RFID is currently the most widely used category. Reading distance can reach 2 meters to 12 meters, with some active tags reaching tens of meters. UHF RFID signals use the UHF frequency band. Frequency regulations vary slightly by country. China uses 920-925MHz. Europe uses 865-868MHz. North America uses 902-928MHz. UHF RFID supports high-speed batch reading and is suitable for warehouse logistics, retail checkout, and asset inventory.

Uniqlo is a typical case of large-scale UHF RFID application. All store merchandise is embedded with RFID tags, achieving automatic inbound and outbound inventory, smart fitting room recommendations, and automatic checkout. The cost of each tag has dropped to just a few cents in RMB, making large-scale application economically feasible.

Differences Between Active RFID and Passive RFID

Passive RFID tags contain no built-in battery and rely on the reader's RF field for power. They have simple structure, low cost, and long lifespan. Currently about 90% of RFID applications use passive tags. The reading distance of passive UHF tags is typically 2 to 6 meters, with prices ranging from a few cents to a few RMB.

Active RFID tags come with battery power. They actively transmit RF signals and do not rely on reader power. Reading distance can reach tens of meters or even over a hundred meters. The disadvantages of active tags are high cost, large size, and limited battery life. They are suitable for container tracking, vehicle management, and large asset monitoring scenarios. There is also a type of semi-passive tag (BAP), where the battery only maintains chip data, while communication still relies on reader signals.

Core Application Scenarios

Warehouse logistics is the most mature implementation area for RFID. After pallets and turnover boxes are affixed with RFID tags, goods entering and leaving warehouses do not require manual scanning. As forklifts pass through reading tunnels, the system automatically completes batch inventory. Error rates drop from one in a thousand with manual operations to below one in one hundred thousand.

Anti-counterfeiting and traceability are widely used in the premium liquor, luxury goods, and pharmaceutical industries. Each RFID tag has a globally unique TID (Tag Identifier) that cannot be tampered with. Consumers verify authenticity through NFC phones or dedicated devices. Compared with QR code anti-counterfeiting, RFID is more difficult to replicate.

Asset management covers IT equipment, instruments, and books. Libraries use HF RFID tags for self-service borrowing, returning, and inventory. A single tunnel reader can simultaneously read tag information from dozens of books.

The retail industry is accelerating RFID deployment. Brands such as Zara, Uniqlo, and Nike have fully implemented RFID systems. Tags are attached to hangtags or packaging, running through the entire circulation chain from factory to store. Store staff can complete full-store inventory by scanning a shelf once with a handheld device.

Comparison of RFID with Traditional Barcodes/QR Codes

Barcodes and QR codes are read optically, requiring alignment with the scanner and can only scan one at a time. RFID reads through RF signals without alignment, simultaneously identifying hundreds of tags in batches. It has obvious advantages in efficiency and automation.

Once a traditional barcode label is printed, the information cannot be changed. RFID tags support multiple writes and locks, allowing data to be appended as tags pass through various supply chain stages. This is critical for reverse logistics and full-chain traceability.

In terms of durability, barcodes cannot be read once obscured or damaged. RFID tags' chips have a certain level of protection after packaging and can resist dirt and humid environments. Metal and liquid environments cause significant interference with RFID signals, which is a current technical shortcoming of RFID.

Cost is the natural advantage of barcodes. The cost of an adhesive barcode label is measured in fractions of a cent. The cost of passive RFID tags ranges from a few cents to a few RMB, approximately tens of times that of barcodes. Whether to implement RFID depends on whether the value of reading efficiency and data management can cover the tag cost.

Future Trends and Considerations

RFID tag prices are still on a declining track. UHF tag costs have approached the 1 RMB threshold, and are expected to enter the sub-yuan era in the coming years. Continued cost reduction will drive RFID penetration into more small and medium-scale scenarios.

Advances in printed antenna technology are an important driving force. The application of digital printing technology in RFID antenna manufacturing is becoming increasingly mature. Flexible tags can directly use conductive ink to print antennas, reducing packaging costs.

RFID tags are not a universal solution for all scenarios. Metal and liquids cause reflection and absorption of RF signals, leading to tag reading failures. During selection, it is essential to choose anti-metal tags or specialized packaging methods based on the material characteristics of the items being tagged. At the same time, data security and privacy protection are also key industry concerns. RFID chips with encryption functions and tag destruction mechanisms are becoming standard configurations.

Lexiang Packaging supports custom RFID adhesive labels. Providing digital printing · fast proofing · variable data services. Can be integrated with NFC anti-counterfeiting solutions and UHF logistics tag projects.