Application of absorbing materials in RFID——rfid absorber

After more than ten years of development in China’s rfid absorber industry, the technology is now relatively mature, especially in the past two years. Under the background of the country’s active encouragement and vigorous promotion of the healthy development of the industry, with the continuous advancement of various factors to the Internet of things, it has maintained a steady upward development trend.


The industry has also reached a consensus on the formulation of frequency standards for rfid absorbers. At present, the commonly used frequency in the world is 13.56MHz. Because of its stable performance and reasonable price, the high-frequency RFID technology of 13.56MHz has a reading distance range that matches the actual application distance range, so it has been widely used in bus cards and mobile payment. application.


RFID absorber electronic tags are often used in metal environments. When RFID absorber electronic tags are close to metal, due to the strong reflectivity of metal to electromagnetic waves, the signal will be weakened, and the reading distance will become closer, causing serious interference. Card reading will fail. The current common solution is to paste a layer of magnetic absorbing material on the back of the electronic label. RFID absorbers are widely used in various aspects such as noise reduction, wave absorption and EMC of electronic equipment.


The composition of the RFID system

The RFID system consists of an electronic tag or a non-contact smart card (such as a smart phone with a swipe card function) placed on an identified object and a device that issues instructions to the electronic tag and collects feedback information from the electronic tag. The device is also known as RFID card reader or reader is composed of two parts. In order to allow other devices to display or use these data, an interface with RS232 protocol can generally be installed on the reader, so that information can be transmitted with external devices.

rf shielding fabric rfid ferrite absorber sheet

Since it is a passive electronic tag, the energy required for the chip and memory in the electronic tag to work needs to be provided by the reader. The communication between the reader and the electronic tag is realized through the principle of electromagnetic coupling. The energy of the electronic tag It is generated by the electromagnetic coupling of the reader coil antenna.


The high-frequency electromagnetic field is generated by the reader’s antenna coil, and then the magnetic field passes through the coil cross-section and the space around the coil. According to the use frequency of the tag 13.56MHz, its wavelength is 22.1m, which is much larger than the distance between the reader and the electronic tag, so the electromagnetic field between the reader and the antenna can be treated as a simple alternating magnetic field.


By adjusting the antenna coil and capacitor of the electronic tag to form a resonant circuit, it is tuned to the transmission frequency 13.56MHz specified by the reader, so that according to the resonance of the circuit, the voltage generated by the coil inductance in the tag reaches the maximum value. The power transmission efficiency between the antenna coil of the reader and the electronic tag is proportional to the number of turns of the coil in the tag, the area enclosed by the coil, the relative angle of the placement of the two, and the distance between them. The reason why the RFID absorber tag reading distance has a certain limit.


For RFID absorber electronic tags used at 13.56MHz, its maximum read and write distance is usually about 10 cm. Because as the frequency increases, the required inductance of the coil of the electronic tag shows a decrease in the number of turns of the coil, usually at this frequency, the typical number of turns is 3 to 10 turns.


The reading distance of RFID absorber tags is not only related to itself, but also has a great relationship with its environment. When using an inductively coupled RFID system, it is often required that the antenna of the reader or electronic tag be mounted directly on the metal surface. However, it is not possible to mount a magnetic antenna directly on a metal surface.

rf shielding fabric rfid ferrite absorber sheet

Because the magnetic flux of the antenna passes through the metal surface, an induced eddy current will be generated. According to Lenz’s law, the eddy current will react to the antenna and rapidly attenuate the magnetic field on the metal surface, so that the data between the reader and the electronic tag can be read. The distance will be severely affected, and there may even be misreads or read failures. The result is the same regardless of the magnetic field generated by the coil mounted on the metal surface itself, or the field approaching the metal plate from the outside (the electronic tag is on the metal surface).


The rfid absorber materials mentioned in this article are mainly aimed at the magnetic conductors used to provide a path for the magnetic field in civil electronic equipment. It has the characteristics of low-pass filter and so on. However, due to its advantages of flexibility and convenient installation, it has been favored by more and more R&D engineers.


As the international standards for electromagnetic interference control become more and more strict, my country is also in line with international standards, and has accelerated the management of electromagnetic noise, especially electronic products. So how to realize electronic products to meet these requirements will be an important course. After years of development, rfid absorber materials have made great progress. However, as the requirements for electronics are getting higher and higher, absorbing materials will also develop in terms of thin thickness, high performance and light weight under the premise of higher and higher frequency of use, which is also the driving force for material advancement.


Since its establishment, Penghui has been focusing on the research of electromagnetic absorber, Wireless charging ferrite, flexible absorbent material and other products. We are a professional emc absorber material manufacturer. Our products have the characteristics of absorbing electromagnetic waves, increasing magnetic flux, resisting metal interference, and isolating magnetic fields. Widely used in wireless charging, RFID, NFC, EMC and other fields of electronic products. Please contact PH Functional Materials if required.

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