Long-distance range recognition
The long-distance range recognition is opposite in the traditional strip code, magnetism card and the IC card says proposes, has the recognition to be away from far, the non- contact, the reading speed quick, does not have the attrition, the environmental effect, the life is not been long, is advantageous for the use characteristic and has guards against the conflict function, can simultaneous working many cards. In overseas, the long-distance range recognition technology has been widely applied in the industrial automation, the commercial automation, the transportation control management and so on the multitudinous domain.
The long-distance range recognition system is composed by three parts:
1. Label (Tag, namely long-distance range radio frequency card): Are composed by the matching plug and the chip in, the label includes sets at the antenna, uses in carrying on the correspondence with the radio frequency antenna between.
2. The long-distance range reads the card: Reading (also may read in the label information equipment in read-write card).
3. Antenna: Transmits the radio-frequency signal in between the label and reader
Some systems also (on position machine host system) connect through microreader RS232 or the RS485 connection with exterior computer, carry on the data exchange.
The system basic work flow is: Microreader through transmitting antenna transmission certain frequency radio-frequency signal, when the radio frequency card enters the transmitting antenna working space produces the induced current, the radio frequency card obtains the energy to activate; The radio frequency card information and so on own code sets at through the card in transmits the antenna to transmit; The system receiving antenna receives to the intelligence signal which transmits from the radio frequency card, transmits after the antenna regulator to the microreader, the microreader carries on the demodulation and the decoding to the receive signal then delivers the backstage host system to carry on correlation processing; The main system judges this card according to the logic operation the validity, makes corresponding processing and the control in view of the different hypothesis, sends out the command signal control implementing agency movement.
In coupling way (inductance - electromagnetism), correspondence flow (FDX, HDX, SEQ), from radio frequency card to microreader data transmission method (load modulation, backscattering, higher harmonic) as well as aspect and so on frequency range, the different non- contact transmission method has the basic difference, but all microreaders in the function principle, as well as very are all similar from this in the decision design structure, all microreaders may the Jian Huawei high frequency connection and the control unit two basic modules. The high frequency connection contains the transmitter and the receiver, its function includes: Has the high frequency emissive power by to start the radio frequency card and to provide the energy; Carries on the modulation to the transmitting message, uses in the data transfer for the radio frequency card; The receive and the demodulation comes from the radio frequency card high frequency signal. The different radio frequency recognition system high frequency connection design has some differences, inductive coupling system high frequency connection schematic diagram like chart 1 shows.
The microreader control unit function includes: Carries on the correspondence with the application system software, and the execution application system software sends in order; Control and radio frequency card course of communications (host - from principle); The signal arranges the decoding. Also has to some special systems carries out the counter- collision algorithm, must transmit the data to between the radio frequency card and the microreader to carry on the encryption and the decipher, as well as carries on radio frequency between the card and microreader attachment function and so on identification authentication.
The long-distance range recognition system read-write distance is a very essential parameter. At present, long-distance range radio frequency recognition system price also very expensive, therefore seeks enhances its read-write distance the method to be very important. The influence radio frequency card read-write distance factor including the antenna operating frequency, the microreader RF output, the microreader receiving sensitivity, the radio frequency card power loss, the antenna and the acceptor Q value, the antenna direction, the microreader and the radio frequency card coupling degree, the energy and the transmission information energy which as well as radio frequency card itself obtains and so on. The majority system reading is away from and reads in the distance is different, reads in is away from probably is reading the distance 40% ~ 80%.
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