RFID electronic tag system
Electronic label system A non-contact automatic recognition technology
Concept
Electronic tag is a non-contact automatic identification technology. It uses RF signals to identify target objects and obtain relevant data. The identification work does not require manual intervention. As a wireless version of barcode, RFID technology has the advantages of waterproof, antimagnetic, high temperature resistant, long service life, large reading distance, data on the tag can be encrypted, larger storage capacity, and free change of storage information that are not available in barcode. The encoding, storage, reading and writing methods of electronic labels are different from those of traditional labels (such as barcode) or manual labels. The encoding of electronic labels is stored in read-only or read-write format on the integrated circuit; Especially for the read-write mode, the electronic tag is realized by wireless electronic transmission. The outstanding technical characteristics of RFID tags are: they can identify a single very specific object, unlike bar codes, which can only identify a class of objects; Multiple objects can be read at the same time, while the barcode can only be read one by one; The amount of information stored is large; With radio frequency, data can be read through external materials, while barcode must read information on the surface of material media by laser or infrared.
Component
(1) Tag. It is composed of coupling components and chips. Each tag has a unique electronic code. High capacity electronic tags have user writable storage space and are attached to objects to identify target objects.
(2) Reader. A hand-held or fixed device that reads (and sometimes writes) label information.
(3) Antenna. The RF signal is transmitted between the tag and the reader.
Classification
Electronic tags can be divided into three categories according to the different ways of information injection for internal storage: integrated circuit fixed mode, field wired rewriting mode and field wireless rewriting mode; According to the technical means of reading the data of electronic tags, they can be divided into three categories: broadcast transmission type, double frequency type and reflection modulation type; According to the different energy supply modes (battery power supply), RFID technology can be divided into active, passive and semi active. The popular classification method of RFID is that it can be divided into low frequency (LF), high frequency (HF), ultra-high frequency (UHF) and microwave frequency band (MW) according to different working frequencies (unit: Hz).
(1) The working frequency of low/high frequency system is generally less than 30MHz, and typical working frequencies are 125kHz, 225kHz, 13.56MHz (non-contact IC card - working frequency of RF card), etc. RFID systems based on these frequencies generally have corresponding international standards, and their basic characteristics are: low cost of electronic labels, less data stored in the labels, short reading distance (passive case, typical reading distance is 10cm), various shapes of electronic labels (card, ring, button, pen), and weak reading antenna directivity.
(2) The operating frequency of UHF/microwave system is generally>400MHz, and the typical operating frequency bands are 915MHz, 2450MHz, 5800MHz, etc. The system is also supported by numerous international standards in these frequency bands. The basic characteristics are: high cost of electronic tags and readers, large amount of data stored in tags, long reading distance (up to several meters to more than ten meters), good adaptability to high-speed movement of objects, generally card shaped appearance, and strong directionality of reading antennas and electronic tag antennas.
(3) The battery is installed in the active electronic tag, which generally has a long reading distance. The disadvantage is that the battery life is limited (3~10 years); There is no battery in the passive electronic tag. After receiving the microwave signal from the reader (readout device), it converts part of the microwave energy into DC power for its own work. Generally, it can be maintenance free. Compared with the active system, the passive system is slightly limited in the reading distance and the speed of the object movement.
(4) The information in the integrated solidified electronic tag is generally injected into the ROM process mode during the production of integrated circuit, and the information saved is unchanging; Field wired rewritable electronic labels generally write the information saved in the electronic labels into their internal E2 storage area. When rewriting, special programmers or writers are required, and they must be powered during the rewriting process; Field wireless rewritable electronic tags are generally applicable to active electronic tags with specific rewriting instructions. The information stored in the electronic tags is also located in the E2 storage area. Generally, the time required to rewrite the electronic tag data is much longer than the time required to read the electronic tag data. Generally, the time required for overwriting is seconds, and the reading time is milliseconds.
(5) Radio frequency identification system. The electronic tag must work in an active way and broadcast its stored identification information to the outside in real time. The reader is equivalent to a receiver that only receives but does not send. The disadvantage of this system is that the electronic tag needs to continuously transmit information, which not only consumes electricity, but also causes electromagnetic pollution to the environment, and the security of the system is poor. It is difficult to realize the double frequency RFID system. Generally, the reader sends out RF query signal, and the signal carrier frequency returned by the electronic tag is the multiple frequency of the RF sent by the reader. This working mode provides convenience for the reader to receive and process the echo signal. However, for passive electronic tags, the energy conversion efficiency of electronic tags is low when they convert the received RF energy of readers to the carrier frequency of frequency doubled echo. Improving the conversion efficiency requires higher microwave skills, which means higher electronic tag costs. At the same time, this system must occupy two working frequency points, and it is generally difficult to obtain the product application license from the Radio Frequency Regulatory Commission.
(6) The realization of reflection modulation RFID system is mainly to solve the problem of receiving and transmitting on the same frequency. When the system is working, the reader sends out a microwave query (energy) signal. The electronic tag (passive) rectifies part of the received microwave query energy signal into DC power for the circuit in the electronic tag to work. The other part of the microwave energy signal is reflected back to the reader after being modulated by the data information (ASK) stored in the electronic tag. After receiving the amplitude modulation signal reflected back, the reader will extract the identification data information stored in the electronic tag. In the working process of the system, the reader sends microwave signal and receives amplitude modulation signal reflected back at the same time. The reflected signal strength is much weaker than the transmitted signal, so the technical difficulty lies in the same frequency reception.