Detailed explanation of RFID technology principle and RFID tag antenna
Time：2021-09-28 15:48:40 Author：Suzhou Cowin Antenna Electronics Click：
1、 Principle of RFID antenna technology
After the tag enters the RF field of the reader / writer, the induced current obtained by the RFID tag antenna is used as the power supply of the chip through the boost circuit. At the same time, the induced current with information is transformed into a digital signal through the RF front-end circuit and sent to the logic control circuit for processing. The information to be replied is sent from the tag memory, sent back to the RF front-end circuit through the logic control circuit, and finally sent back to the reader / writer through the antenna.
2、 RFID tag antenna in RFID system
From the principle of RFID technology, the key to the performance of RFID tag lies in the characteristics and performance of RFID tag antenna. Antenna plays a key role in the data communication between tag and reader. On the one hand, when the chip start-up circuit of the tag starts to work, it needs to obtain enough energy in the electromagnetic field generated by the reader through the antenna; On the other hand, the antenna determines the communication channel and communication mode between the tag and the reader. Therefore, the research of antenna, especially the antenna inside the tag, has become the focus.
3、 Design requirements of RFID tag antenna
The design requirements of RFID tag antenna mainly include: the physical size of the antenna is small enough to meet the needs of tag miniaturization; Having omnidirectional or hemispherical coverage directionality; A chip with high gain that can provide the largest signal to the label; Good impedance matching. No matter what direction the tag is in, the polarization of the tag antenna can match the signal of the reader / writer; It has robustness and low cost. When selecting the antenna, we mainly consider: the type of antenna, the impedance of the antenna, the RF performance applied to the item, and the RF performance when other items surround the labeled item.
4、 Category of RFID tag antenna
According to the power supply mode of RFID tag chip, RFID tag antenna can be divided into active antenna and passive antenna. The performance requirements of active antenna are lower than those of passive antenna, but its performance is greatly affected by the battery life: passive antenna can overcome the limitation of active antenna by battery, but it has high requirements for the performance of antenna.
It is mainly divided into three categories: coil type, dipole type and slot type. Coil antenna is to coil the metal wire into a plane or wind the metal wire on the magnetic core; The dipole antenna consists of two straight wires of the same thickness and equal length arranged in a straight line. The signal is fed from the two ends in the middle, and the length of the antenna determines the frequency range; The slot antenna is composed of grooves cut out from the metal surface. The microstrip patch antenna is composed of a circuit board with a rectangle at the end. The length and width of the rectangle determine the frequency range.
After the tag enters the RF field of the reader / writer, the induced current obtained by the RFID tag antenna is used as the power supply of the chip through the boost circuit. At the same time, the induced current with information is transformed into a digital signal through the RF front-end circuit and sent to the logic control circuit for processing. The information to be replied is sent from the tag memory, sent back to the RF front-end circuit through the logic control circuit, and finally sent back to the reader / writer through the antenna.
2、 RFID tag antenna in RFID system
From the principle of RFID technology, the key to the performance of RFID tag lies in the characteristics and performance of RFID tag antenna. Antenna plays a key role in the data communication between tag and reader. On the one hand, when the chip start-up circuit of the tag starts to work, it needs to obtain enough energy in the electromagnetic field generated by the reader through the antenna; On the other hand, the antenna determines the communication channel and communication mode between the tag and the reader. Therefore, the research of antenna, especially the antenna inside the tag, has become the focus.
3、 Design requirements of RFID tag antenna
The design requirements of RFID tag antenna mainly include: the physical size of the antenna is small enough to meet the needs of tag miniaturization; Having omnidirectional or hemispherical coverage directionality; A chip with high gain that can provide the largest signal to the label; Good impedance matching. No matter what direction the tag is in, the polarization of the tag antenna can match the signal of the reader / writer; It has robustness and low cost. When selecting the antenna, we mainly consider: the type of antenna, the impedance of the antenna, the RF performance applied to the item, and the RF performance when other items surround the labeled item.
4、 Category of RFID tag antenna
According to the power supply mode of RFID tag chip, RFID tag antenna can be divided into active antenna and passive antenna. The performance requirements of active antenna are lower than those of passive antenna, but its performance is greatly affected by the battery life: passive antenna can overcome the limitation of active antenna by battery, but it has high requirements for the performance of antenna.
It is mainly divided into three categories: coil type, dipole type and slot type. Coil antenna is to coil the metal wire into a plane or wind the metal wire on the magnetic core; The dipole antenna consists of two straight wires of the same thickness and equal length arranged in a straight line. The signal is fed from the two ends in the middle, and the length of the antenna determines the frequency range; The slot antenna is composed of grooves cut out from the metal surface. The microstrip patch antenna is composed of a circuit board with a rectangle at the end. The length and width of the rectangle determine the frequency range.