The radio frequency recognition technology is a kind of non-contact automatic diagnosis technology. It is by the electronic tag (Tag/Transponder), the read-write (Reader/Interrogator) and the middleware (Middle-Ware) ~ part composition kind of short-distance range wireless communication system. The tag in radio frequency identification is the combination of radio frequency identification tag chip and tag antenna. The tag according to its working mode is different and divided into active tag and passive tag.In addition, the tag antenna design must also consider the application of the electronic tag occasion, such as the application in the metal object surface tag antenna and the application in the ordinary object surface tag antenna in the antenna structure and the selection of materials there are great differences. Suitable for a variety of chips, low cost, multi-purpose tag antenna is one of the key technology of radio frequency recognition in our country to get wide popularity.

Radio frequency identification system and antenna classification

For the use of passive tag radio frequency identification system, according to the different working frequency band has two kinds of working mode. One is the inductive coupling (Induc.tiveCoupling) T work mode, this mode is also called near field work mode, it is mainly applied to low frequency and high frequency RFID system: The other is the backscattering (Backscattering) 32 work mode, this mode is also called far field T work mode, mainly applied to UHF and microwave RFID system.

The inductive coupling mode mainly refers to the reader antenna and the label antenna both adopt the coil form. When the read-write is reading the label, sends out the unmodulated signal. In the read-write antenna near field electronic label antenna receives the signal and activates the label chip after, by the label chip according to the internal storage the global unique identification number (ID) controls the label antenna in the current size. This current size further enhances or reduces the reader antenna sends out the magnetic field. At this time, read-write's near-field component exhibits the modulation characteristic, read-write internal circuit check barium 0 to this modulation quantity which produces because of the label and demodulate and get the label information.

In the backscatter T work mode, the read-write and the electronic label between uses the electromagnetic wave to carry on the information transmission. When the read-write carries on the reading recognition to the label, first sends out the electromagnetic wave without modulation, at this time is located in the far field electronic label antenna receives the electromagnetic wave signal and produces the induction voltage on the antenna, the electronic label internal circuit will this induction voltage carries on the rectification and amplifies for activates the label chip. When the tag chip activation, with its own global unique identification number on the tag chip impedance changes, when the impedance of the electronic tag chip and the tag chip between the impedance match is good when the basic does not reflect the signal, and the impedance match is not good will be almost all reflected signal. So that the reflected signal appears amplitude change, this situation is similar to the reflected signal for amplitude modulation processing. The reader judges the electronic label identification number and carries on the recognition by receiving the reflected signal after modulation. This kind of antenna mainly includes microstrip antenna, plane dipole antenna and ring antenna. Figure 2 is our development can work in many kinds of recognition environment UHF electron label antenna.