RFID Antenna and Processing
The RFID system is mainly composed of a reader (target), a transponder (RFID tag) and a back-end computer. Among them, the reader implements reading and writing of the tag's data and storage. It consists of a control unit, a high-frequency communication module and an antenna. It is mainly composed of an integrated circuit chip and an external antenna. The circuit chip usually includes circuits such as a radio frequency front end, logic control, and memory. According to the principle of power supply, tags can be divided into active (acTIve) tags, semi-active (semiacTIve) tags, and passive tags. Passive tags are popular because of their low cost and small size.
The basic working principle of the RFID system is: After the tag enters the reader and transmits the RF field, the induction current obtained by the antenna is used as the power source of the chip after the boost circuit, and the induction current with information is converted into a digital signal by the RF front-end circuit. It enters the logic control circuit for processing, and the information that needs to be returned 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 via the antenna.
3 Antenna in RFID system
From the principle of RFID technology, the key to the performance of RFID tags lies in the characteristics and performance of RFID tag antennas. The key role in the data communication process between the tag and the reader is the antenna. On the one hand, the tag's chip start circuit starts to work, and the antenna needs to obtain sufficient energy in the electromagnetic field generated by the reader; 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 internal antennas of tags, has become the focus.
3.1 Types of RFID System Antennas
According to the power supply method of RFID tag chips, RFID tag antennas can be divided into active antennas and passive antennas. The performance requirements of active antennas are lower than passive antennas, but their performance is greatly affected by battery life: passive antennas can overcome the limitations of active antennas that are limited by batteries, but they have high requirements on the performance of the antennas. At present, the research focus of RFID antennas is passive antennas. Divided from the operating frequency band of the RFID system, in the LF and HF bands (such as 6.78 MHz and 13.56 MHz), the transmission of electromagnetic energy is completed in the induction field area (like a stable field), which is also called an inductive coupling system ; In the UHF section (such as 915MHz, 2400Mttz) Z system, the transmission of electromagnetic energy is completed in the far-field area (radiation field), also known as microwave radiation system. Due to the different energy generation and transmission methods of the two systems, the corresponding RFID tag antennas and front-end parts have their own particularities, so tag antennas are divided into near-field induction coil antennas and far-field radiation antennas. The inductive coupling system uses a near-field inductive coil antenna, which consists of a multi-turn inductive coil. The inductive coil and a capacitor connected in parallel form a parallel resonant loop to couple the maximum RF energy. The types of far-field radiating antennas used in microwave radiation systems are mainly They are dipole antennas and slot antennas. Far-field radiation antennas are usually resonant and generally take half wavelengths. The shape and size of the antenna determine the frequency range and other properties it can capture. The higher the frequency, the more sensitive the antenna and the less area it occupies. Higher operating frequencies can have smaller tag sizes, and far-field radiating antennas have higher radiation efficiency than near-field induction antennas.
RFID tag antenna
RFID tag antenna is a transponder antenna for RFID electronic tags, and it is a communication induction antenna. The RFID electronic tag transponder which is generally completed with a chip. RFID tag antennas are divided into metal-etched antennas, printed antennas, and copper-plated antennas due to their different materials and manufacturing processes.
In the past few years, printed antennas have been relatively popular. Later, due to the unreliable consistency of the electrical performance of the finished products, coupled with service life, etc., they were gradually eliminated from the market. Although printed antennas have the advantage of short production cycles. In recent years, with the development of nanotechnology, nano-silver paste antennas have appeared. However, due to reliability issues, the market has been delayed.
Etching method: circuit substrate (PET + aluminum foil) compounding → curing → circuit printing and UV curing → etching → ink removal and cleaning → circuit conduction processing → coil slitting → circuit characteristic inspection → inspection packaging;
Printing method: PET film → circuit printing and UV curing → coil slitting → circuit characteristic inspection → inspection packaging.
RFID antenna manufacturing technology mainly has three methods: etching, coil winding and printed antenna. Among them, RFID conductive ink printed antenna is a new technology developed. The above manufacturing methods of RFID tag antennas are respectively applicable to RFID electronic tag products with different frequencies. The low frequency LF RFID electronic tag antenna is basically made by winding. The high frequency HF RFID electronic tag antenna can be realized by the above three methods, but it is mainly an etched antenna. Its material is generally aluminum or copper. UHF UHF RFID electronic tag antennas are mainly printed antennas.