The most basic RFID system consists of three parts:
1. Tag (RF card): consists of a coupling component and a chip. The tag contains a built-in antenna for communication with the RF antenna.
2. Reader: A device that reads (and can also write in the card) the tag information.
3. Antenna: Pass RF signals between the tag and the reader.
Some systems also connect to an external computer (host computer system) through the RS232 or RS485 interface of the reader for data exchange.
The basic working process of the system is: the reader transmits a certain frequency of the radio frequency signal through the transmitting antenna, and when the radio frequency card enters the working area of ​​the transmitting antenna, an induced current is generated, and the energy obtained by the radio frequency card is activated; the radio frequency card transmits the information such as its own code through the card. The antenna is sent out; the receiving antenna of the system receives the carrier signal sent from the RF card, and transmits it to the reader through the antenna adjuster, and the reader demodulates and decodes the received signal and sends it to the background main system for related processing; the main system According to the logic operation, the legality of the card is judged, corresponding processing and control are performed for different settings, and a command signal is issued to control the action of the actuator.
Different in coupling mode (inductor-electromagnetic), communication flow (FDX, HDX, SEQ), data transmission method from RF card to reader (load modulation, backscatter, higher harmonics) and frequency range The contactless transmission method is fundamentally different, but all readers are similar in terms of functional principle and thus the design and construction. All readers can be simplified into two basic modules: high frequency interface and control unit. The high frequency interface includes a transmitter and a receiver, the functions of which include: generating high frequency transmit power to activate the radio frequency card and providing energy; modulating the transmit signal for transmitting data to the radio frequency card; receiving and demodulating the radio frequency card from the radio frequency card High frequency signal.
The functions of the reader's control unit include: communicating with the application system software and executing commands sent by the application system software; controlling the communication process with the RF card (master-slave principle); encoding and decoding of the signals. For some special systems, there are also anti-collision algorithms, encryption and decryption of data to be transmitted between the RF card and the reader, and additional functions such as authentication between the RF card and the reader.
The read/write distance of the RFID system is a key parameter. Currently, long-distance radio frequency identification systems are expensive, so it is important to find ways to increase their read and write distances. Factors affecting the reading and writing distance of the RF card include the antenna operating frequency, the reader's RF output power, the reader's receiving sensitivity, the power consumption of the RF card, the Q value of the antenna and the resonant circuit, the antenna direction, and the coupling of the reader and the RF card. Degree, as well as the energy obtained by the RF card itself and the energy of the transmitted information. The reading distance and writing distance of most systems are different, and the writing distance is about 40% to 80% of the reading distance.
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