RFID wireless identification electronic tag basic introduction

Radio frequency identification technology is a non-contact automatic identification technology. Its basic principle is to use the transmission characteristics of radio frequency signal and spatial coupling (inductive or electromagnetic coupling) or radar reflection to realize automatic identification of the identified object.

The RFID system contains at least two parts: electronic tags and readers. The electronic tag is the data carrier of the radio frequency identification system, and the electronic tag is composed of a tag antenna and a special chip for the tag. According to the different power supply methods of electronic tags, electronic tags can be divided into active electronic tags (Active tag), passive electronic tags (Passive tag) and semi-passive electronic tags (Semi-passive tag). Active electronic tags are equipped with batteries, passive radio frequency tags do not have internal batteries, and semi-passive tags (Semi-passive tags) partially rely on batteries to work.

Electronic tags can be divided into low-frequency electronic tags, high-frequency electronic tags, ultra-high-frequency electronic tags and microwave electronic tags according to different frequencies. According to the different packaging forms, it can be divided into credit card labels, linear labels, paper labels, glass tube labels, circular labels and special-purpose special-shaped labels.

The RFID Reader (reader) communicates wirelessly with the RFID electronic tag through the antenna, which can read or write the tag identification code and memory data. A typical reader consists of a high-frequency module (transmitter and receiver), a control unit and a reader antenna.

Among them, electronic tags are also called radio frequency tags, transponders, and data carriers; readers are also called reading devices, scanners, communicators, and readers (depending on whether electronic tags can rewrite data wirelessly). The space (contactless) coupling of the radio frequency signal is realized between the electronic tag and the reader through the coupling element. In the coupling channel, according to the timing relationship, the energy transmission and data exchange are realized.

There are two types of coupling of RF signals that occur between the reader and the RFID tag.

(1) Inductive coupling. Transformer model, which realizes coupling through high-frequency alternating magnetic field in space, based on electromagnetic induction law.

(2) Electromagnetic backscatter coupling: radar principle model, the emitted electromagnetic waves are reflected after hitting the target, and carry back target information at the same time, based on the spatial propagation law of electromagnetic waves.

The inductive coupling method is generally suitable for short-range RFID systems that work at medium and low frequencies. Typical operating frequencies are: 125kHz, 225kHz and 13.56MHz. The identification action distance is less than 1m, and the typical action distance is 10-20cra.

The electromagnetic backscattering coupling method is generally suitable for long-distance radio frequency identification systems operating at high frequencies and microwaves. Typical operating frequencies are: 433MHz, 915MHz, 2.45GHz, 5.8GHz. The identification action distance is greater than 1m, and the typical action distance is 3-l0m.