What is the purpose of Xiaomi Motorola's vying to launch the air charging technology?

We know that the current mass-produced mobile phones have two charging methods: wireless and wired, but they are all limited by distance. Needless to say wired charging, the mobile phone must be connected to the charging cable and charging head when charging, so we inevitably need to consider the length of the charging cable when charging the mobile phone. I believe that many of my friends have been embarrassed by the fact that the charging cable is not long enough when they are lying on the bed while playing with their mobile phones.

In addition to the above-mentioned pain points of wired charging, wireless charging also has some inconveniences. Although wireless charging solves the problem of interface and connection, in the scene of charging and playing, wireless charging is not even as convenient as wired charging. Therefore, many mobile phone manufacturers have been studying better charging solutions. Recently, with the successive releases of Motorola and Xiaomi, a technology called air charging has received widespread attention.

小米隔空充电
Mi Air Charge

Motorola and Xiaomi vying to release the “black technology”

On the morning of January 29th, the general manager of Lenovo’s mobile phone business department in China, @ Magical Jinge, introduced Motorola’s air charging technology through a video. In the video, when two mobile phones are placed 1 meter away from the Motorola charging transmitter, the mobile phones show that they are not charging. But when the phone is placed at a distance of 1 meter from the transmitter, the phone starts charging. Then when the other phone was placed 80 cm away from the transmitter, the second phone also started charging. We can see from the video that Motorola’s air-to-air charging technology supports simultaneous air-charging of multiple mobile phones.

摩托罗拉展示隔空充电技术
Motorola showcases air-to-air charging technology

Soon after Lenovo released the Motorola mobile phone charging video, Zeng Xuezhong, vice president of Xiaomi Group and president of the mobile phone department, also officially released its “black technology” for charging. Zeng Xuezhong introduced that air charging is realized through Xiaomi’s self-developed air charging pile, which has 5 built-in phase interference antennas, which can position the mobile phone in millisecond space and accurately detect the position of the mobile phone. A phase control array composed of 144 antennas is used through beam The forming will transmit the millimeter wave to the mobile phone directionally, and the mobile phone can receive it through the micro beacon antenna, which can realize 5 watts long-distance charging within a few meters. Xiaomi owns 17 technical patents for the entire self-developed system.

What is the mystery of air charging

Space charging, we already know the general working condition of this technology from the literal understanding, that is, no charging cable or even charging base is needed. As long as there are charging facilities within a certain distance, the mobile phone can be charged invisibly. Does it sound special? Cool? However, this technology sounds easy, but it is not easy to implement.

隔空充电
Air charge

In fact, air charging is also a type of wireless charging. Wireless charging technology is mainly divided into three categories, electromagnetic induction technology, electromagnetic resonance technology and radio frequency technology. At present, the most common wireless charging technology is electromagnetic induction technology, which mainly uses electromagnetic coils for energy conversion and transmission. For example, all kinds of wireless charging boards and wireless charging bases all use this technology, and the Qi standard we are familiar with is based on this technology. One of the biggest features of electromagnetic induction technology is its high charging efficiency, and the conversion rate is usually around 80%. However, its drawbacks are also obvious, that is, the mobile phone must be close to the charging board, it is difficult to play while charging.

隔空充电可边充边玩
You can play while charging

Electromagnetic resonance technology is slightly further than electromagnetic induction in the charging distance, which can allow wireless charging of about 10cm, but the charging efficiency is relatively low, and the conversion rate is about 70%. At present, there are some charging boards on the market that allow users to be fixed on the bottom of the desk, and the mobile phone can be charged when placed on the desk, which uses electromagnetic resonance technology. Motorola and Xiaomi’s recently released space charging technology is the third wireless radio frequency technology. The principle of this type of technology is to use the space electric field as the medium of energy transmission, so that there can be a significant breakthrough in the charging distance. It can also become more flexible.

Take Xiaomi’s air charging as an example. The core of this technology lies in space positioning and air energy transmission. Its self-developed air charging pile has built-in 5 phase interference antennas, which can position mobile phones in millisecond space and accurately detect mobile phones. Position, a phase control array composed of 144 antennas, through beamforming to directionally transmit millimeter waves to the mobile phone. On the mobile phone side, Xiaomi has also self-developed the miniaturization design of the antenna array. The built-in beacon antenna and receiving antenna array can convert millimeter wave signals into electrical energy, and finally realize air-space charging.

毫米波转换电能
Millimeter wave conversion electric energy

At present, Xiaomi’s air charging can achieve 5W long-distance charging for a single device within a radius of several meters, and multiple devices can also be charged, even if foreign objects are blocked without reducing the charging efficiency. Soon, Xiaomi’s air-to-air charging technology can also charge smart watches, Bands and other wearable devices. In the future, small smart home products such as speakers and desk lamps can be wirelessly powered, and the living room will truly enter the wireless era.

In Motorola’s air charging solution, the transmitter is more compact, about the same size as a common wireless charging base, and can charge multiple devices at the same time. However, Motorola has not announced the specific power of its air charging solution.

小米自研隔空充电技术
Xiaomi self-developed space charging technology

Large-scale commercial use will take time

The concentrated appearance of the two mobile phone manufacturers’ air charging technology is actually a result of a long accumulation of technology. The real large-scale commercialization of this technology will take time. We can see that there are still many challenges in the large-scale commercial use of space charging in the consumer field. From the demonstration video of Xiaomi, it can be seen that the “air charging pile”, that is, the transmitting terminal device for air charging, is currently relatively large, and the process is relatively complicated, and the radio frequency materials used are also relatively expensive.

How to reduce the cost of charging facilities while taking into account the transmission power, frequency and conversion rate, so that consumers can accept it, is still an urgent problem to be solved. In addition, at the technical level, air charging still needs to be further improved and improved, and the search and positioning of the device must be more accurate, because the actual application situation is very complicated, which further increases the requirements for positioning accuracy.

小米隔空充电技术
Mi Air Charging Technology

In addition to technical problems, there are also health issues that consumers have been paying attention to. At present, many people believe that the radio waves in wireless charging have an impact on human health, but in fact these radio waves are almost harmless to the human body. For example, millimeter wave is different from α, γ and β rays. It does not produce a chemical reaction to the irradiated object, and thus does not cause any DNA changes in the object. And there is currently no experimental data that shows that millimeter wave radiation will have a negative impact on human health.

If the space charging technology is to be commercialized on a large scale, it is also necessary to solve the cost problem, improve the technical accuracy and further popularize the essence of the technology to the public.