Radio Frequency IdenTIficaTIon (RFID) is a non-contact automatic identification technology that automatically recognizes target objects and acquires relevant data through radio frequency signals. The identification work can be performed in various harsh environments without manual intervention. UHF RFID technology can be used to identify high-speed moving objects and to identify multiple tags at the same time.
UHF RFID tag standard
1. ISO/IEC 18000-6 defines the UHF physical layer and communication protocol; the air interface defines Type A and Type B; supports read and write operations.
2. EPCglobal defines the structure of the electronic article code and the UHF air interface and communication protocols, such as class0, Class1Gen1, ClassGen2.
3. UbiquitousID, a Japanese organization that defines the structure and communication management protocol for UID encoding.
First, the frequency standard of RFID
Frequency license
The operating frequency of the RF system is one of the most basic technical parameters of the RFID system. The choice of operating frequency largely determines the scope of application, technical feasibility and system cost of electronic tags.
The RFID system is, in the final analysis, a radio propagation system that must occupy a certain spatial communication channel. In the spatial communication channel, the intelligence of the radio frequency signal is expressed in the form of electromagnetic coupling or electromagnetic reflection. Therefore, the performance of the radio frequency identification system is inevitably affected by the spatial transmission characteristics of the electromagnetic wave.
In people's daily lives, electromagnetic waves are everywhere, such as aircraft navigation, radio broadcasting, military applications, and so on. China is managed by the National Radio Management Committee (referred to as the No. Committee). Therefore, the production and use of radio products must be approved by the state.
Second, the frequency division
Since many fields of application require the system to operate within a certain frequency range, the frequency needs to be segmented. In recent years, segmentation of the spectrum has been carried out several times, the most common of which is established by the Institute of Electrical and Electronics Engineers (IEEE), which states that radio frequency identification systems are part of the radio application and therefore their use cannot interfere with other For the normal operation of the system, the frequency range used by the ISM is usually the local radio communication band. Therefore, in general, the frequency band used by the radio frequency is the ISM band.
The most important operating frequency of the RFID system is 0-135k, the ISM frequency is 6.78MHZ\13.56MHZ\27.125MHZ\40.68MHZ\433.92MHZ\869.0MHZ\915MHZ\2.45GHZ\5.8GHZ and 24.125GHZ.
Below we mainly introduce the frequency bands 869MHZ and 915MHZ.
At present, the global UHF RFID system operates at frequencies between 860 and 960. This is because RFID systems will be used all over the world. However, there is no common frequency that can be applied to a radio frequency identification system in the world. The specific provisions of the aspects are also different. Therefore, frequency issues are an important issue for RFID systems. The frequency problem mainly includes the range of operating frequency, the size of the transmitting power, the frequency modulation technology, and the channel width.
The frequency band is 869MHz, allowing short-distance use, such as postal, conference, etc. The bands 888-889 and 902-928 are widely used by radio frequency identification systems. In addition, the frequency band in which the next adjacent frequency band is occupied by D-network telephones and cordless telephones is uniformly planned and allocated by the International Telecommunication Union (ITU). The ITU divides the world into three regions, which are respectively Region 1 (Europe and Africa), Region 2 (Americas), Region 3 (Oceania and Asia).
The characteristics of UHF RFID tags are as follows:
1. Ultra-high frequency electronic tags transmit energy through an electric field. The energy of the electric field drops not very fast, but the area read is not well defined. The reading distance of this band is relatively long, and the passive can reach about 10m, mainly through capacitive coupling for energy exchange and data transmission.
2. The electric wave in the ultra-high frequency band cannot pass many materials, especially suspended particles such as water, dust and fog.
3. The antenna of the electronic tag is generally strip and label. The antenna is available in both linear and circular polarization to meet the needs of the application.
4. This band has a good read range, but it is difficult to define the read area.
5. It has a high transmission rate and can read a large number of electronic tags in a short time.
Third, UHF RFID electronic tag composition
The electronic tag can be divided into two parts, namely the chip of the electronic tag and the antenna of the tag. The antenna function is the electromagnetic wave emitted by the mobile phone reader into the space and the energy emitted by the chip itself is emitted by electromagnetic waves; the function of the chip is to adjust and decode the signals received by the tag, and the electronic tag needs to be returned. The signals are encoded, modulated, and the like.
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