What is RFID
RFID (Radio Frequency Identification, the abbreviation RFID), radio frequency identification technology is a kind of automatic identification technology in the 1990 of the 20th century began, radio frequency identification technology is using radio waves through-space coupling (alternating magnetic field or electromagnetic field) free contact and the transmission of information to achieve identification technology. From the basic principles of information transmission, radio frequency identification technology in low frequency band based on transformer-coupled model (energy and signal transmission between primary and secondary), in the high frequency spatial coupling model based on radar target (radar electromagnetic signal with the target after the targeted information back to the radar receiver). 1948 halisituokeman published "the communication by means of reflected power" lays the theoretical foundation of radio frequency identification radio frequency identification technology.   
Edit this paragraph the development of radio frequency identification technology
1940-1950 years: improvement and application of radar led to the radio frequency identification technology in 1948, lays the theoretical foundation of radio frequency identification technology.   1950-1960: early stage of radio frequency identification technology, mainly in laboratory experiments.   1960-1970: the theory of radio frequency identification technology has been developed, starting some application. 1970-1980: radio frequency identification technology and product development in a period of great development, testing of radio frequency identification technology to speed up.   There were some of the earliest radio frequency identification applications.   1980-1990: radio frequency identification technology and products into commercial applications, and applications of all sizes began to appear.   1990-2000: RFID standardization is increasingly important, RFID products have been widely used, RFID product has become part of people's lives.   After 2000: standardization and more attention, radio frequency identification products more varied, active RFID, passive RFID tags and semi passive electronic tags have been developed, tag costs are reduced and applications to expand the scale. So far, radio frequency identification technology is enriched and perfected. Single-chip RFID tags, RFID tag reading, wireless read-write distance, passive electronic labels to identify, adapt to the fast-moving objects RFID technology and products is becoming a reality and to apply.   
Edit this paragraph RFID frequency guidelines and typical
different band RFID products have different characteristics, the following details of passive sensors in different frequency characteristics and main applications. Currently defines the operating frequency RFID products have low frequency, VHF and UHF frequency ranges meet different standards for different products and different band RFID products have different characteristics.   Which sensors are passive and active in two ways, the following details of passive sensors in different frequency characteristics and main applications. And low frequencies (from 125KHz to 134KHz) in fact first in low frequency RFID technology has been widely used and promoted. This work is mainly carried out by means of inductively coupled, where reader coil there is a transformer and inductor coil coupling. Reader alternating field effects through induction voltage is rectified in the sensor antenna, can be used as supply voltage.   Magnetic fields can be well defined, but field declines too quickly. Characteristics: 1. Working in low-frequency sensors frequency and from 120KHz to 134KHz, TI's work at 134.2KHz.   This band of wavelengths around 2500m.   2. in addition to metal material impact, generally low frequencies can pass through any material without reducing the reading distance.   3. work in low frequency reader/writer in the world without any special license restrictions. 4. low-frequency product has different packages.   Well the package is too expensive, but have more than 10 years service life.   5. Although the frequency of the magnetic field region soon, but have a relatively uniform area of reading and writing.   6. the RFID product relative to the other bands, the band data transfer rate is slower.   7. sensors the price expensive compared with other bands. Main applications: 1. Livestock management system 2. Car alarm keyless entry system and application 3. Application of Marathon systems 4. Automatic parking and vehicle management systems 5. Application of the automatic refueling system 6. Hotel door lock system 7. Access control and security management systems in line with international standards: a) ISO 11784 RFID application of animal husbandry structure b-coding) ISO-11785 RFID animal husbandry technology c) ISO 14223-1 RFID livestock applications of d-air interface) application-protocol-defined ISO 14223-2 RFID animal husbandry e) ISO 18000-2 defined low frequency physical layer, anti-collision and protocols f) DIN 30745 Main is the application-defined European waste management standards II, high frequency (frequency of 13.56MHz) in the frequency of the sensor is no longer requires winding coil, corrosion the printing of ways that you can make an antenna. Sensors generally work by way of load modulation. Through sensors the load resistance of connect and disconnect the reader antenna voltage changes, using remote sensors of the antenna voltage is amplitude modulation.   If people connect and disconnect data controlled load voltage, then these data can be transmitted from the sensors to the reader. Characteristics: 1.   Operating frequency is 13.56MHz, the frequency wavelength is about 22m. 2. in addition to metal, but the frequency wavelengths can pass through most materials, but tends to reduce the read range.   Sensor away from metal for a distance.   3. the band has been recognized in the world and there are no special restrictions.   4. sensors in the form of tags.   5. Although the frequency of the magnetic field region soon, but have a relatively uniform area of reading and writing.   6. this system has the anti-collision feature, you can read multiple tags simultaneously.   7. can write some data information label.   8. data transmission rates faster than low frequency, the price is not expensive. Main applications: 1. Application of book management system 2. Management application of the gas cylinder 3. Apparel production management and logistics systems and applications 4. Three-meter prepaid system 5. Hotel management and application of lock 6. Conferences lane system 7. Fixed assets management system 8. Medical logistics systems management and application 9.   Intelligent shelf management in line with international standards: a) ISO/IEC 14443 IC card coupled, maximum reading distance is 10cm.   B) ISO/IEC 15693 drain coupling IC card, maximum reading distance is 1M.   C) ISO/IEC 18000-3 standard defines the physical layer of the 13.56MHz system, anti-collision algorithms and protocols.   D) 13.56MHz ISM Band Class 1 defines the 13.56MHz defined by the EPC-compliant interface. C, UHF (frequency is between 860MHz to 960MHz) UHF system uses electric fields to transmit energy. Farm energy decline is not fast, but the reading area is not very well defined. The band read the far distance, passive up to about 10m.   Mainly through capacitive coupling approach to implementation. Characteristics: 1. In the band, the global definition is not quite the same-Europe and parts of Asia-defined frequency 868MHz, defines the frequency band between 902 to 905MHz in North America, Japan proposed frequency band between 950 to 956.   This band of wavelengths around 30cm. 2. at present, the definition of band power output at present (United States definition is 4W, defined as 500mW in Europe).   May limit will go up to 2W EIRP in Europe. 3. the UHF band radio wave through many materials, especially water, dust, fog suspended particulate material.   Relative to the high-frequency RFID tag, tag does not need the band and metal ones. 4. RFID tag antennas are generally long and label-shaped.   Antennas are linear and circular polarization of the two designs to meet different application requirements.   5. this band have a good read, but reading is difficult to define.   6. has a high data transfer rate, in a very short time can read electronic tags. Main applications: 1. Supply chain management and application 2. Product line management and application 3. Management and application of air parcel 4. Management and application of container 5. Management and application of railway parcel 6.   Application of logistics management system in line with international standards: a) ISO/IEC 18000-6 defines the physical layer and Protocol of UHF air interface Type a and Type b are defined in two parts; support for read and write operations. B) EPCglobal defined electronic goods coding structure and VHF air interfaces and communications protocols.   For example: Class 0 and Class 1, UHF Gen2.   C) Ubiquitous ID Japan organization, defines the UID code structure and communication protocol. In the future, the UHF RFID products will get a lot of applications.   For example, WalMart, Tesco, United States Department of Defense and the Metro supermarket in their supply chain applications of RFID technology. Active RFID technology (2.45GHz, 5.8G), active RFID with low transmitter power, long distance, data volume, characteristics of high reliability and compatibility, compared with passive RFID, the technological advantage is obvious.   Widely used in applications such as highway tolls, cargo management.   As a new automatic identification technology, RFID, has huge development potential in China. Radio frequency identification technology (RFID,Radio Frequency Identification) are actually automatic identification technology (AEI,Automatic Equipment Identification) in the field of radio technology application and development. The basic idea of this technique is that by using some advanced technology, people on all kinds of objects or devices (people, objects) in different States (mobile, stationary or harsh environments), automatic identification and management.

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