RFID Technology Principles and Detailed Explanation of RFID Tag Antennas

　　RFID Technology Principles and Detailed Explanation of RFID Tag Antennas

　　1. RFID Antenna Technology Principles

　　After the tag enters the reader to transmit the RF field, the induced current obtained by the RFID tag antenna is used as the power supply of the chip after passing through the boost circuit. At the same time, the induced current with information is converted into a digital signal through the RF front-end circuit and sent to the logic control circuit for processing. The information that needs 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 through the antenna.

　　2. RFID tag antenna in RFID system

　　From the perspective of RFID technology principles, the key to RFID tag performance lies in the characteristics and performance of RFID tag antennas. The antenna plays a key role in the data communication process between the tag and the reader. On the one hand, the chip startup circuit of the tag starts working, and 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 method between the tag and the reader. Therefore, the research on antennas, especially the antenna inside the tag, has become the focus.

　　3. Design requirements for RFID tag antennas

　　The design requirements for RFID tag antennas mainly include: the physical size of the antenna is small enough to meet the needs of miniaturization of tags; it has omnidirectional or hemispherical coverage; it has high gain and can provide the maximum signal to the tag chip; the impedance matching is good, no matter what direction the tag is in, the polarization of the tag antenna can match the signal of the reader; it has robustness and low cost. When selecting an antenna, the main considerations are: the type of antenna, the impedance of the antenna, the RF performance applied to the item, and the RF performance when there are other items around the tagged item.

　　4. Categories of rfid tag antennas

　　According to the power supply method of the RFID tag chip, RFID tag antennas can be divided into two categories: active antennas and passive antennas. The performance requirements of active antennas are lower than those of passive antennas, but their performance is greatly affected by battery life: passive antennas can overcome the shortcomings of active antennas limited by batteries, but the performance requirements of antennas are very high.

　　It is mainly divided into 3 categories: coil type, dipole type, and slot type. A coil antenna is a metal wire coiled into a plane or wrapped around a magnetic core; a dipole antenna is composed of two straight conductors of the same thickness and length arranged in a straight line, and the signal is fed from the two middle endpoints. The length of the antenna determines the frequency range; a slot antenna is composed of a groove cut out of the metal surface, and a microstrip patch antenna is composed of a circuit board with a rectangle at the end, and the length and width of the rectangle determine the frequency range.