Radio Frequency Identification System

- May 18, 2018-

RFID system RFID system

An automatic identification system consisting of radio frequency tags, readers, and computer networks. Generally, the reader emits energy in an area to form an electromagnetic field. When the radio frequency tag detects the signal of the reader when passing through this area, it sends the stored data. The reader receives the signal sent by the radio frequency tag and decodes and verifies the accuracy of the data. To achieve the purpose of identification.

Technical editing

Initially in the technical field, transponders are electronic modules that can transmit information to reply information. In recent years, due to the rapid development of radio frequency technology, transponders have new ideas and meanings, and are also called smart labels or tags. The reader (reader) of the RFID electronic elevator certificate wirelessly communicates with the RFID electronic tag through the antenna, and can read or write the tag identification code and memory data. A typical reader includes a high-frequency module (transmitter and receiver), a control unit, and a reader antenna.

RFID radio frequency identification is a non-contact automatic identification technology. It automatically identifies target objects and obtains relevant data through radio frequency signals. The identification work can be performed in various harsh environments without manual intervention. RFID technology can identify high-speed moving objects and can identify multiple labels at the same time. The operation is quick and easy.

Tag: Composed of a coupling element and a chip, each tag has a unique electronic code and is attached to the object to identify the target object.

Reader: A device that reads (sometimes writes) tag information and can be designed as a handheld rfid reader (eg C5000W) or a stationary reader.

Antenna: Passes RF signals between tags and readers.

How it works

After the tag enters the magnetic field, it receives the RF signal from the reader, sends the product information (Passive Tag, passive tag or passive tag) stored in the chip by the energy obtained by the induced current, or actively sends a certain frequency by the tag. Signal (Active Tag, active tag or active tag). The reader reads the information and decodes it, and sends it to the central information system for data processing.

A complete RFID system consists of three parts: a reader and a tag (TAG), a so-called transponder, and an application software system. The working principle is that Reader emits a specific frequency. The radio wave energy is given to the Transponder to drive the Transponder circuit to send the internal data. At this point, the Reader receives the decoded data in sequence and sends it to the application program for processing.

The communication between the RFID card reader and the electronic tag and the energy sensing method can be roughly divided into two types: Inductive Coupling and Backscatter Coupling. Most low-frequency RFIDs use the first type, and higher frequencies use the second method.

The reader can be a read or read/write device depending on the structure and technology used, and is an RFID system information control and processing center. The reader is usually composed of a coupling module, a transceiver module, a control module, and an interface unit. Half-duplex communication is generally used for information exchange between the reader and the transponder, and the reader is coupled to the passive transponder to provide energy and timing. In practical applications, management functions such as collection, processing, and remote transmission of object identification information may be further implemented through Ethernet or WLAN. The transponder is the information carrier of the RFID system. At present, transponders are mostly composed of coupled originals (coils, microstrip antennas, etc.) and microchips constituting a passive unit.

Working mode edit

The basic working methods of radio frequency identification systems are divided into Full Duplex and Half Duplex systems and Sequence (SEQ) systems. Full duplex means that the RFID tag and reader can transmit information to each other at the same time. Half-duplex indicates that the RF tag and the reader can transmit information in both directions, but can only transmit information in one direction at the same time.


In full-duplex and half-duplex systems, the RF tag's response is transmitted in the presence of electromagnetic fields or electromagnetic waves emitted by the reader. Since the signal of the radio frequency tag is weak at the receiving antenna compared to the signal of the reader itself, an appropriate transmission method must be used in order to distinguish the signal of the radio frequency tag from the signal of the reader. In practice, data transmission from RFID tags to readers typically uses load reflection modulation techniques to load RF tag data onto the reflected echo (especially for passive RF tag systems).

In contrast to the timing method, the radiated electromagnetic field from the reader is periodically switched off. These intervals are identified by the RF tag and used for data transmission from the RF tag to the reader. In fact, this is a typical way of working with radar. The disadvantage of the time sequence method is that the energy supply of the radio frequency tag is interrupted when the reader sends a pause, which must be compensated by loading a sufficiently large auxiliary capacitor or an auxiliary battery.

Working frequency editing

The frequency that is usually used when the reader transmits is referred to as the operating frequency of the RFID system. The common operating frequencies are low frequency 125kHz, 134.2kHz and 13.56MHz. Low-frequency system generally refers to its operating frequency is less than 30MHz, the typical operating frequency: 125KHz, 225KHz, 13.56M, etc., these frequency applications of radio frequency identification systems generally have the corresponding international standards to support. Its basic characteristics are the low cost of electronic tags, the small amount of data stored in the tags, the short reading distance, the variety of electronic tags (cassettes, loops, buttons, and pens), and the lack of read antenna orientation. Wait.

The high frequency system generally refers to its operating frequency is greater than 400MHz, the typical working frequency band is: 915MHz, 2.45GHz, 5.8GHz and so on. High frequency systems are also supported by numerous international standards in these frequency bands. The basic characteristics of the high-frequency system are the high cost of electronic tags and readers, the large amount of data stored in the tags, and the longer reading distance (up to a few meters to ten meters). It is suitable for high-speed motion performance of objects, and its appearance is usually a card. The shape of the reading antenna and the electronic tag antenna have strong directionality.

System advantage editing

RFID is a flexible application technology that is easy to operate, simple and practical, and particularly suitable for automatic control. The identification work requires no manual intervention. It can support both read-only and read-write work modes without contact or aiming. Freedom to work in all kinds of harsh environments: Short-range RF products are not afraid of bad environment such as oil stains and dust pollution. They can replace bar codes, such as tracking objects on the factory's assembly line; long-range RF products are mostly used for traffic, and the distance can be identified. Up to tens of meters, such as automatic charging or identification of vehicle identities. The radio frequency identification system mainly has the following system advantages:

Reading is quick and easy: The reading of the data does not require a light source, and can even be performed through the outer packaging. The effective identification distance is larger. When the active label with its own battery is used, the effective identification distance can reach more than 30 meters;

Fast recognition speed: When the tag enters the magnetic field, the reader can instantly read the information, and can process multiple tags at the same time to realize batch identification;

Large data capacity: The two-dimensional barcode (PDF417) with the largest data capacity can only store up to 2725 digits; if it contains letters, the amount of storage will be less; RFID tags can be expanded to dozens of K according to the needs of users;

Long service life and wide range of applications: Its radio communication means can be used in dusty, oily and other highly polluted and radioactive environments, and its closed packaging greatly extends the life span of printed barcodes;

Tag data can be changed dynamically: The programmer can write data to the reader, giving the RFID tag the power of an interactive portable data file, and it can write less time than a printed bar code.

Better security: not only can be embedded or attached to different shapes and types of products, but also can set password protection for reading and writing of tag data, thus having higher security;

Dynamic real-time communication: The tag communicates with the reader at a frequency of 50 to 100 times per second. Therefore, as long as the RFID tag is attached to an object within the effective recognition range of the reader, it can dynamically track and monitor its position. .