In recent years, various new applications based on NFC/RFID technology have ushered in an unprecedented high-speed growth period, especially the current extremely hot mobile payment market. Compared with the transaction value of US dollars, the growth rate reached 38%, and in the foreseeable future, the global mobile payment market will still maintain a compound growth rate of about 40% and continue to run fast. NFC flexible absorbent material plays an important role.
The potential of the market is undoubtedly huge, but it is also because of NFC/RFID, a technological industry driven by technology. It has to be said that there are still many insurmountable technical obstacles in today’s NFC/RFID, which is also an important reason for hindering the further expansion of the market.
Currently, one material used to solve the interference problem is a flexible absorbent material. Generally speaking, magnetic materials are divided into permanent magnetic materials (Hc>1000A/m) and soft magnetic materials (Hc<100A/m), while NFC/RFID designs use soft magnetic materials, that is, wave-absorbing materials. This article mainly introduces the absorbing material to overcome the NFC/RFID antenna interference problem.
What is the specific function of the so-called flexible absorbent material? When NFC/RFID is working, the magnetic field formed by the antenna is easily interfered by metal and other objects, resulting in unnecessary deviations in device identification, and the use of HFC flexible absorbent material can well eliminate this error. For example, the NFC/RFID antenna is generally placed between the back cover of the mobile phone and the battery, and the battery is likely to interfere with the magnetic field. At this time, we only need to put a layer of flexible absorbent material between the antenna and the battery to eliminate the adverse effects of this interference. Moreover, NFC ferrite and flexible absorbent material also have a large number of applications in wireless charging and EMI. These materials can well solve the interference problems of various applications such as RFID/NFC/wireless charging! It has promoted the continuous and rapid development of the Internet.
The magical use of flexible absorbent material in electromagnetic protection
With the development of electronic equipment in the direction of miniaturization and higher data rate, the spacing between components is getting smaller and shorter, and the wavelength is constantly shortening. This leads to an increase in the “antenna effect” of the noise when the wavelength is shortened to approach the physical size of the components and devices. Therefore, preventing noise coupling into these “antenna” structures that can radiate or generate coupled fields becomes even more important, as at higher frequencies it becomes more difficult to implement electromagnetic protection of products in a cost-effective manner。
Reduce edge scatter on printed circuit boards (PCBs)
The microwave flexible absorbent material is laid along the edge of the printed circuit board, which can reduce the edge radiation caused by the edge, and does not need to occupy an additional area of the circuit board. Absorbers also reduce the likelihood of board resonance problems by dissipating energy that is not reflected back into the board. The absorbing material can be fixed by opening a U-shaped groove on the edge of the circuit board.
Reduce trace radiation on PCB board
Placing the absorber directly above the microstrip line eliminates field radiation from above the trace. Applying pressure-sensitive adhesive (PSA) to the traces with absorbing material can reduce the field coupling to the chassis. The placement of the absorbing material in this way has little effect on the impedance of the traces, because the flexible absorbent material has high impedance characteristics (greater than 10Ω). The absorber can also be conveniently placed directly on top of the traces without any additional mounting or mechanical fastening measures. This method has been used on a switch box, and the radiated emission can be reduced by about 4~6dB when the frequency is 6GHz.
Reduce cavity resonance effect
By gradually absorbing energy and converting it to heat, absorbers reduce radiation or “shield” while reducing the Q factor in a cavity. It is more convenient to use flexible absorbent material, because it converts electromagnetic energy into heat energy without using “grounding” measures. As long as the absorbing material blocks the field or is placed in the field’s propagation path, it can reduce the electromagnetic energy of the field. An additional effect of adding absorbing material to the cavity is that it changes the effective dielectric constant of the cavity, depending on how much material is added. As the proportion of the material volume in the cavity increases, it will have a greater impact on the composite permittivity. By changing the effective permittivity, the position of the resonant frequency point can be shifted. This technique was used in the design of a switch box, resulting in an energy reduction of about 6dB at 8.5 GHz.
Radiator
Generally speaking, the physical and electrical dimensions of the heat sink are larger than the high-frequency chip device, and it is bonded to the high-frequency chip device, so it is a high-efficiency radiator. No matter how well the signal travels on the pc board, if the chip’s currents are parasitically coupled to the heat sink, radiated emissions will occur. Each heat sink of the radiator is equivalent to a monopole dipole antenna structure, and all heat sinks are equivalent to an antenna array. Depending on the overall shielding effectiveness or the resonant effects of the radiator, these emissions may or may not exceed the code limit. The most common way to control the radiated emissions of heatsinks is to connect the “ground” of the heatsink to the reference ground of PCBs.
Shenzhen PH Functional Materials is an absorber sheet manufacturer. With many years of production experience, we are one of the experts in this industry. Our products mainly include flexible whiteboard, wireless charging ferrite, RF absorber materials, etc. If you are interested in our products, please contact us.
