How much do you know about RFID antennas

The Internet of Things is regarded as the third wave of the information industry after computers and the Internet. In the process of its realization, it requires the joint efforts of many high-tech technologies such as communication, sensors, RFID, and positioning. The combination of RFID and Internet, communication and other technologies can realize the tracking and information sharing of global items, so it is considered to be an important cornerstone of the realization of the Internet of Things, and is listed as one of the top ten important technologies in the 21st century.

In the process of realizing wireless communication, antenna is an essential component. RFID uses radio waves to transmit information, and the generation and reception of radio waves need to be completed through antennas. When the electronic tag enters the working area of the reader antenna, the electronic tag antenna will generate enough induced current to obtain energy and be activated. For RFID systems, the antenna is a crucial part, which is closely related to the performance of the system.

For example, in a warehouse management project, the cost of RFID Antennas accounts for less than 1% of the overall cost. However, if you choose an RFID antenna with poor performance in order to reduce costs blindly or for other reasons, and choose an RFID antenna with poor performance, problems such as unstable reading, missed reading, cross-reading, and reading failure will easily occur during the layout of the RFID antenna. In this case, not only will the cost not be reduced, but it will increase several times. Therefore, when the RFID system is deployed, it is necessary to pay attention to the RFID antenna.

What types of RFID antennas are there?

The antennas of the RFID system can be roughly divided into two categories: electronic tag antennas and reader antennas. These two types of antennas can also be subdivided into omnidirectional antennas and directional antennas according to the directionality. According to the difference in shape, they can also be divided into linear antennas. and planar antennas, etc. The RFID Reader antenna needs to have the characteristics of broadband and circular polarization. In the low-frequency and high-frequency bands, electronic tags and readers basically use coil antennas, generally using copper wires. However, due to the high frequency used by high frequency, the number of turns of the antenna will be much less than that of low frequency, which makes the production of high frequency RFID antenna simpler and lower in price. In the ultra-high frequency band, more etching processes are used, including copper etching antennas and aluminum etching antennas, and the processes are relatively mature. In the microwave frequency band, the form of antenna is more diverse, including symmetrical dipole antenna, microstrip antenna, array antenna, broadband antenna and so on.

Different frequency bands and different application fields have different requirements for the structure of the electronic tag antenna. In general, antenna design tends to follow the following goals:

(1) The volume of the antenna should be miniaturized as much as possible;

(2) The antenna provides as large a signal as possible to the chip;

(3) The directivity of the antenna coverage is as large as possible;

(4) The polarization of the antenna matches the interrogation signal of the reader;

(5) The price of the antenna should be as low as possible and so on.

Three main processes of RFID antenna manufacturing

In order to meet the different requirements of RFID performance parameters in different application scenarios, various RFID antenna manufacturing processes have emerged. At present, the most commonly used RFID antenna manufacturing processes mainly include coil winding method, etching method and printing method.

(1) Coil winding method

When using the coil winding method to make an RFID tag antenna, it is necessary to wind the tag coil on a winding Tool and fix it, which requires a large number of turns of the antenna coil, and the coil can be either a circular ring or a rectangular ring. . This method is generally used for RFID tags in the frequency range of 125 to 134KHz. The disadvantages of using this processing method to make antennas are obvious, which can be summarized as high cost, low production efficiency, and insufficient consistency of processed products.

(2) Etching method

Copper or aluminum is often used to make antennas by etching, which is close to the etching process of flexible printed circuit boards in terms of production process. Etching method can be applied to the mass production of 13.56MHz, UHF bandwidth electronic tags, which have the advantages of fine lines, low resistivity, good weather resistance, and stable signals. However, the shortcomings of this method are also obvious, such as cumbersome production procedures and low production capacity.

(3) printing method

The printed antenna is a circuit that directly prints conductive lines on an insulating substrate (or film) with conductive ink to form an antenna. The main printing methods have been extended from only screen printing to offset printing, flexographic printing, gravure printing and other production methods. The printing method is suitable for mass production of electronic tags in the 13.56MHz and RFID UHF frequency bands. It is characterized by fast production speed, but due to the high resistance of the circuit formed by conductive ink, its application range is limited to a certain extent. Due to the advancement of printed antenna technology, the cost of RFID tags has been effectively reduced, which has promoted the popularization of RFID applications.

The future development trend of RFID antenna

(1) Size miniaturization

With the development of intelligent requirements and process technology, the size of RFID antennas is still developing in the direction of miniaturization. In low-frequency and high-frequency electronic tags, the size of the antenna is often much larger than the chip. Therefore, the size of the tag is often restricted by the size of the antenna. From the perspective of market demand, the miniaturization of RFID tags is also conducive to its entry into more application scenarios.

(2) Mass production

Compared with the traditional process, conductive ink printing antenna has lower cost and more efficient production, which is mainly reflected in the low price of materials used in conductive ink, and the printing equipment used in the screen printing process is also cheaper than etching equipment. In addition, this printing process is simple and quick to operate, and the entire process is relatively simple, which is more suitable for mass production.

(3) The process is green and environmentally friendly

In addition, the chemical attack reaction in the etching process will produce waste, which is easy to cause pollution to the environment. In contrast, the conductive ink printing technology is much more environmentally friendly.

(4) Lower cost

If RFID wants to achieve larger-scale applications, the cost needs to be further reduced. Because many times people are not out of consideration for RFID technology, but it is difficult to accept the high cost pressure behind the electronic tag. Now conductive ink technology can make RFID applications out of the cost dilemma, greatly reducing the production cost of RFID antennas. It is foreseeable that the combination of RFID antenna production and advanced printing technology will be closer in the future.

With the development of conductive ink and printing technology, RFID printing antenna technology will be further popularized. This will help reduce the cost of RFID tags, thereby lowering the application threshold of RFID, promoting the implementation of RFID technology in all walks of life, and bringing the Internet of Things world with everything connected to it as soon as possible.