RFID Tag Antenna
RFID system antenna can be divided into RFID tags antenna and read-write antenna two categories, these two types of antenna according to the direction can also be subdivided into omnidirectional antenna and directional antenna, etc., according to the shape difference can also be divided into line antenna and surface antenna, etc. RFID read-write antenna need to have wide band, circular polarization characteristics. In the low frequency and high frequency band, the rfid tag and the read-write basically are all uses the coil antenna, generally uses the copper wire. However, due to the high frequency use of high frequency, the antenna winding circle number will be much less than the low frequency, which makes the high frequency RFID antenna production more simple, the price is also lower some. In the UHF band, more etching processes are used, including copper etched antennas and aluminium etched antennas, and the process is more mature. In the microwave band, the antenna form is more diverse, including symmetrical oscillator antenna, microstrip antenna, array antenna, broadband antenna and so on.
Different frequency bands, different applications for rfid tag antenna structure form requirements also vary. In general, antenna design tends to follow the following objectives.
(1) the antenna volume as small as possible;
(2) The antenna provides as large a signal as possible to the chip;
(3) The directionality of the antenna coverage is as large as possible;
(4) The polarization of the antenna can match the interrogation signal of the reader;
(5) antenna price as low as possible and so on.
The three main processes of RFID antenna manufacturing
In order to meet the different requirements of RFID performance parameters for different application scenarios, various RFID antenna manufacturing processes have emerged. At present, the most commonly used RFID antenna manufacturing process mainly has coil winding method, etching method and printing method three.
(1) Coil winding method
With the coil winding method to produce RFID tag antenna, to wind the tag coil on a winding tool and fixed, the number of turns of the antenna coil is required, the coil can be both circular ring, can also be a rectangular ring. This method is generally used for RFID tags in the frequency range of 125 to 134 KHz. The disadvantages of using this processing method to produce antennas are obvious, mainly can be summarized as high cost, low production efficiency, the consistency of the processed product is not good enough, etc.
(2) Etching method
Etching method commonly used copper or aluminium to produce antennas, this method in the production process and flexible printed circuit board etching process is close to. Etching method can be used in the manufacture of a large number of 13.56MHz, UHF band width of the rfid tag, it has a fine line, low resistivity, good weather resistance, signal stability and other advantages. However, the disadvantages of this method are also obvious, such as cumbersome production procedures, low capacity, etc.
(3) Printing method
Printed antenna is directly with conductive ink in the insulating substrate (or film) printed on the conductive lines, the formation of the antenna circuit. The main printing methods have been extended from screen printing only to offset printing, flexographic printing, gravure printing and other production methods. The printing method is suitable for mass production of RFID tags in the 13.56MHz and RFID UHF bands. It is characterised by fast production speed, but due to the high resistance of the circuit formed by the conductive ink, it is somewhat limited in its application. Due to the advancement of printed antenna technology, the cost of RFID tags has been effectively reduced, promoting the popularity of RFID applications.
RFID antenna future development trend
(1) Size miniaturization
With the development of intelligent demand and process technology, the size of RFID antenna is still 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 constrained by the size of the antenna. From the perspective of market demand, the miniaturisation of RFID tags also facilitates their entry into more application scenarios.
(2) High volume production
Compared with traditional processes, conductive ink printing antennas have a cheaper cost, more efficient production, mainly reflected in the conductive ink used in the material price is very low, screen printing process used in the printing equipment is also cheaper than the etching equipment. Plus this printing process is simple and quick to operate, the whole process is also relatively simple, more suitable for mass production.
(3) Green process
In addition, the chemical erosion reaction in the etching process will produce waste, which can easily cause pollution to the environment, compared to the conductive ink printing technology is much more environmentally friendly.
(4) Lower cost
The cost of RFID needs to be further reduced in order to achieve larger scale adoption. Because many times people are not out of consideration for RFID technology, but difficult to accept the high cost of electronic tags behind the pressure. 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 even closer in the future.
With the development of conductive ink and printing technology, RFID printed antenna technology will become further popular. This will help to reduce the cost of RFID tags, thus reducing the application threshold of RFID, promoting RFID technology in all walks of life, so that the Internet of things connected to the early arrival of the world of things.