Radio frequency identification devices(RFID) technology is a non-contact automatic identification technology. It consist of the Tag/Transponder, Reader/Interrogator and Middle-Ware part, which is a short distance wireless communication system. The rfid tag is the combination of rfid tag chip and tag antenna. Tag, according to the different work mode, can be divided into active tags and passive tags. Active label itself batteries provide the energy for the Reader/Interrogator communications: passive tags using inductive coupling or backscattering working mode, namely Reader/Interrogator electromagnetic field and electromagnetic wave available energy to activate the chip through the tag antenna, and it adjust the rfid tag chip and tag antenna matching degree, the information stored in the tag chip, which will feedback to the Reader. So. Rfid tag antenna impedance must and the tag chip input impedance of conjugate matching, then the label chip can maximize access rfid read-write device of electromagnetic energy. In addition, the tag antenna design must also take into account the electronic label application occasions, such as using in the metal tag antenna and in ordinary objects surface, the antenna's structure, its material selection has very big difference. Suitable for a variety of chips, low cost, multi-purpose tag antenna RFID is one of the key technology widely spread all over the world.
Radio frequency identification system and antenna classification
For using passive tags radio frequency identification system, depending on the working frequency band has two kinds of working mode. One a kind of inductive coupling T model, this model is also known as the near field work mode, it is mainly used for low frequency and high frequency RFID system, the other is the Backscattering 32 model, this model is also known as T far field pattern, which mainly is suitable for the uhf and microwave RFID system.
Inductive coupling mode is mainly refers to Reader antenna and the tag antenna using the form of coil. When Reader read labels, it will send modulation signals. the antenna near-field electronic tag antenna receives the signal, it will activate the tag chip, according to the internal storage of global unique identification number (ID) to control the current size. The current size further increase or decrease the magnetic field from the reader antenna. At this time, Reader near field component showed by modulation characteristics, Reader inside electric can get the label information.
In backscattering T mode, the Reader and electronic tags using electromagnetic waves for information transmission. When Reader read labels to identify, it will issued by modulation of electromagnetic waves, at this time, the far field of electronic tag antenna receive electromagnetic wave signal and the output voltage is induced in the antenna, electronic circuit inside will use induction voltage rectifier and amplifier to activate the tag chip. After the tag chip activated, its global unique identification number on the tag chip impedance changes, when the rfid chip impedance and the between impedance matching tag chip is better, then it basic not reflected signal, and the impedance matching is bad, it will almost reflected all the signal. So the reflection signal will have changes, this situation is similar to the reflection signal amplitude modulation. the Reader through received through the reflex of the modulation signal to determine the electronic tag identification number for identification. This kind of antenna mainly include microstrip antenna, plane dipole antenna and loop antenna.
Radio frequency identification system and antenna classification
For using passive tags radio frequency identification system, depending on the working frequency band has two kinds of working mode. One a kind of inductive coupling T model, this model is also known as the near field work mode, it is mainly used for low frequency and high frequency RFID system, the other is the Backscattering 32 model, this model is also known as T far field pattern, which mainly is suitable for the uhf and microwave RFID system.
Inductive coupling mode is mainly refers to Reader antenna and the tag antenna using the form of coil. When Reader read labels, it will send modulation signals. the antenna near-field electronic tag antenna receives the signal, it will activate the tag chip, according to the internal storage of global unique identification number (ID) to control the current size. The current size further increase or decrease the magnetic field from the reader antenna. At this time, Reader near field component showed by modulation characteristics, Reader inside electric can get the label information.
In backscattering T mode, the Reader and electronic tags using electromagnetic waves for information transmission. When Reader read labels to identify, it will issued by modulation of electromagnetic waves, at this time, the far field of electronic tag antenna receive electromagnetic wave signal and the output voltage is induced in the antenna, electronic circuit inside will use induction voltage rectifier and amplifier to activate the tag chip. After the tag chip activated, its global unique identification number on the tag chip impedance changes, when the rfid chip impedance and the between impedance matching tag chip is better, then it basic not reflected signal, and the impedance matching is bad, it will almost reflected all the signal. So the reflection signal will have changes, this situation is similar to the reflection signal amplitude modulation. the Reader through received through the reflex of the modulation signal to determine the electronic tag identification number for identification. This kind of antenna mainly include microstrip antenna, plane dipole antenna and loop antenna.
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