Home Featured Last updated:February 15, 2021Recently, on Jan 29, Xiaomi officially released its self-developed air-to-air charging technology. Putting it in simple words, Air charging in smartphones is that the receiving device does not need any charging cable or even a charging base to charge. Even if it is a few meters away from the transmitting device, it can realize automatic air charging. At the same time, Lenovo’s Motorola also released its own air charging technology. So what is the mystery of the air charging technology in Xiaomi and Motorola? Let’s find out! What's Inside Air Charging Technology in Smartphones – Everything we need to know!Understanding Xiaomi Air Charging TechnologyDifference Between Air Charging Vs Wireless ChargingAir Charging Explanation (Continued.)What’s Different in Xiaomi Air Charging Technology Then The Conventional Air Charging?Understanding Motorolla Air Charging TechnologyXiaomi Air Charging Vs Motorolla Air Charging Technology – What’s the Difference?How is Standard Air Charging Achieved?Q: Is Air Charging Safe for Health? Is Air Charging Dangerous for Humans?Wireless Charging Patent StatisticsAir Charging Phones ListFAQs Air Charging Technology in Smartphones – Everything we need to know! Understanding Xiaomi Air Charging Technology Geek Alert! According to Xiaomi’s official introduction, the core of Xiaomi’s air charging technology lies in space positioning and air energy transmission. Its self-developed aerial charging pile (transmitting end) has built-in 5 phase interference antennas, which can perform millisecond spatial positioning of the smartphone, accurately detect the position of the smartphone (receiving end), and then use a phase control array composed of 144 antennas to pass the beam and transmit millimeter waves to the smartphone in a directional path achieving air-to-air charging. Of course, like the previous wireless charging technology, the smartphone (receiving end) also needs to have built-in corresponding components in order to receive the energy from the transmitting end. Difference Between Air Charging Vs Wireless Charging The difference in air charging vs wireless charging is: Traditional wireless charging smartphone has a built-in coil that comes in contact with the charging base to charge Air charging smartphones have a built-in “beacon antenna” and “receiving antenna array” which receive power via air energy transmission from the receiver Air Charging Explanation (Continued.) Among them, the function of the beacon antenna is to broadcast position information in the space field through low power consumption, so that the transmitter can find the position of the receiver, and then the transmitter transmits millimeter-wave signals directionally through beamforming technology. At this time of writing, the receiving antenna array is composed of 14 antennas built in the smartphone that can convert the millimeter-wave signal from the transmitting end into electric energy through the rectifier circuit to realize the air charging experience. What’s Different in Xiaomi Air Charging Technology Then The Conventional Air Charging? According to reports, the current Xiaomi air charging technology has achieved that multiple devices can be charged at a distance within a radius of several meters at the same time, and the charging power of each device can reach 5 watts, even if it is blocked by foreign objects which can reduce charging efficiency. Only 5W? Although the charging power is only 5W, it has basically met the lower limit charging requirements of current smart and it is a non-inductive charging under the condition that the user’s normal use of the phone is completely unaffected, and the experience far exceeds traditional wireless charging. Of course, we can also see that Xiaomi’s current air charging transmitter is larger in size and the antenna array used internally has a higher specification, so the cost may also be a big challenge. Maybe we might be seeing this in premium flagships priced around $1000+. Understanding Motorolla Air Charging Technology While Xiaomi released its self-developed air charging technology, Motorola also demonstrated its wireless charging technology through video. According to the video, the two Motorola edge smartphones are placed 1 meter and 80 centimeters away from the transmitting end, and they can automatically charge in the air. According to Chen Jin, general manager of Lenovo’s Phones China, Motorola’s air-to-air charging distance is far greater than the current contact charging based on Qi technology, and it has achieved that multiple smartphones can be charged at the same time, similar to Xiaomi’s air charging. Xiaomi Air Charging Vs Motorolla Air Charging Technology – What’s the Difference? The volume of the transmitting end of Motorola’s air charging technology is many times smaller than that of Xiaomi, which is very small and portable, and easy to deploy. Motorola’s air-to-air charging technology cannot penetrate obstacles. After blocking the charging transmitter with the hand, charging stops. While in the case of Xiaomi, air charging can penetrate objects. Why is that so? This is mainly due to the fact that the transmitting end of Xiaomi’s air charging technology not only uses 144 antenna arrays but also applies beamforming technology, that is, targeted transmission to the location of the charged device, which improves the signal strength so that the signal penetration and transmission distance have been improved. This technology is also used in Xiaomi routers as well. In addition, 14 antennas are used at the receiving end, and the sensitivity of signal reception is higher, so it can work normally even if it is blocked. How is Standard Air Charging Achieved? As we all know, wireless charging devices widely used in the market are basically based on the Qi standard introduced by the Wireless Power Consortium (WPC), which is based on magnetic induction technology. However, this technology not only requires a very small separation distance between the receiving end and the transmitting end during wireless charging but also has higher requirements for the placement position. For example, Apple’s newly launched Magsafe wireless charger uses magnetic attraction to closely adhere to and accurately align the wireless charging receiver of the iPhone 12 to achieve stable and efficient wireless charging. It is precise because of the limitations of the magnetic induction wireless charging technology promoted by WPC that wireless charging technologies with higher spatial freedom and longer transmission distances began to appear, mainly including magnetic resonance, radio wave, and light energy. Type 1: Magnetic resonance Charging Technology We all know that tuning forks have an interesting physical property of “resonance”. Each tuning fork has its own sound frequency. When a tuning fork vibrates, if there is another tuning fork with the same sound frequency nearby, it will vibrate even if it is not directly hit. The resonance of the tuning fork can be said to achieve energy transfer. Similarly, magnetic resonance wireless charging uses two resonant circuits with the same vibration frequency to be put together. When one of them starts to oscillate due to energization, the other circuit will also oscillate to “automatically” generate current, and the electrical energy is thus separated. This phenomenon is called “magnetic resonance” and is used for wireless charging. It can charge multiple devices at a distance of several meters, and there is no requirement for the location of the device. As early as four or five years ago, there have been many wireless charging technology companies studying air-space charging technology based on the principle of magnetic resonance. For example, Intel, WiTricity, uBeam, Bose, Huawei, SprouTIng, Ningbo Weie, Shanghai Chushan, Zixiao Technology, Zhonghui Chuangzhi, Taiwan Jiejia, etc. are all developing wireless charging technology based on magnetic resonance. For a long time, the AirFuel Wireless Charging Alliance (composed of the two major alliances of PMA and A4WP) has been pushing hard for magnetic resonance wireless charging technology based on the AirFuel standard 6.78MHz resonant magnetic field, which can cover a power range of about 0-60w. Which brands are on Magnetic Resonance Wireless Charging Technology? According to data, in the AirFuel group, there are Qualcomm, Samsung, Dell, Energous, PowerSphyr, WiTricity, Gill Electronics, Chargifi, RT Tech, and other companies. WPC also includes magnetic resonance technology as its standard. Shanghai Chushan Electronic Technology is focusing on the magnetic resonance wireless charging technology with the kHz-level resonance frequency under the WPC framework. Pros of Magnetic Resonance Wireless Charging System For magnetic resonance wireless charging technology, its advantage is that it can achieve long-distance high-power charging, and the conversion efficiency can reach more than 50%. In addition, the 6.78MHz frequency band used by AirFuel resonance is the lowest of the ISM (Industrial-Science-Medical) frequencies. Therefore, it has no effect on human health. Cons of Magnetic Resonance Wireless Charging System The difficulty lies in adjusting the two circuits to exactly the same frequency and achieving miniaturization and high efficiency. The design of a magnetic resonance wireless charging system requires mastery of advanced technologies such as antenna design capabilities, ultra-high frequency power control systems, resonance management technology, and so on, which requires high technical requirements. Type 2: Radio Wave Charging Technology Radio wave charging technology is mainly based on the principle of RF radio frequency, which conducts electric energy through radio waves with a frequency of about 2.4GHz/5.8GHz. The receiving end needs to receive radio waves through an antenna and convert them into electricity. Pros of Radio Wave Wireless Charging System This technology has the advantages of low cost and can charge multiple devices in the radio frequency coverage at the same time. Cons of Radio Wave Wireless Charging System The disadvantages are: radio frequency transmission is not directional, the transmission efficiency is relatively poor, and it is susceptible to interference. Transmission efficiency is low. It is suitable for devices with low power consumption. The transmission efficiency can be improved by increasing the transmission power, but there will be health problems caused by radiation. Which brands are on Radio Wave Wireless Charging Technology Currently, manufacturers mainly engaged in wireless charging technology based on radio waves include Energous, Ossia, Powercast, GuRu Wireless, etc. Take Energous as an example. As early as 2015, it launched a wireless charging technology called WattUp, which combines FM, Bluetooth, and other patented technologies (2.4/5.8 GHz). Its transmitter can pass low energy Bluetooth and Compatible peripheral equipment for communication and positioning. Once connected, the transmitter can transmit a concentrated RF signal with the same frequency as the Wi-Fi signal. The transmitter converts the current into radio waves for transmission in air, and the receiver uses Wi-Fi and Bluetooth LE to locate the location of the device and connect it to the transmitter. Then converts radio waves into direct current power to charge mobile devices anytime and anywhere. WattUp charging technology can simultaneously provide 2W power transmission for four devices to be charged within a distance of 4.5 meters, while the time consumption is only half of the traditional wiring charging. It is worth mentioning that in February 2019, Vivo has already cooperated with Energous on wireless charging technology. The cooperation is supported by Energous’s WattUp wireless charging technology, and Vivo phones will be able to charge the battery through radiofrequency. In addition, at CES2020, GuRu Wireless of the United States demonstrated prototypes of three different air-to-air charging solutions based on millimeter wave (mmWave) with a higher operating frequency. GuRu said that it can use millimeter wave technology to charge multiple devices a few feet away (1 foot = 30.48 cm), and the charging power can reach several watts, which is comparable to the power used by consumers using traditional chargers. Type 3: Light Energy Charging Technology Last but not least, the light energy method is mainly by converting light energy into electrical energy. Therefore, the place where light energy can be covered can be used for charging, so it can support longer distance charging than the other two types. However, the light can easily be blocked, which also makes this technology have greater limitations. Which Brands are on Light Energy Charging Technology? At present, manufacturers in this segment mainly include Laser Motive, Wi Charge, etc., as well as some research institutions. Among them, the working principle of the Laser Motive product is to use a Laser laser to send a concentrated beam of light to a remote receiver that converts light into electricity through the air or fiber optic cable to convert the laser light into electrical energy. The main difference from solar energy is that Laser Motive uses a high-intensity laser and the energy of laser light is much stronger than the sun. It can be aimed at any place, up to 10 kilometers away. It is currently mainly used for point-to-point energy transmissions, such as on a mountain, communication relay towers, sensors under the sea, drones, electronic equipment in military areas or oil fields, power supply for rockets, space shuttles, etc., to achieve economical and safe power supply the way. Wi Charge uses infrared to provide a charging function, its charging power can reach 10W, the effective distance is 15 feet (about 457.2 cm). At present, the size of Wi-Charge’s transmitter module is about 17x17mm. In the future, it will work to reduce the size to less than 10x10mm and extend the rechargeable distance to about 9 meters, so that it can cover all the range of general indoor space targeting mainly home appliances. In addition, the research team of Sejong University in South Korea also developed a long-distance wireless charging technology based on infrared rays not long ago. According to reports, this infrared wireless charging technology uses high-power infrared light generated by a semiconductor optical amplifier device to achieve long-distance wireless charging. Its working distance can reach several meters or more. There is almost no loss of energy during the transfer process, and it can select different bands to charge multiple electronic devices at the same time. In addition, infrared wireless charging does not generate electromagnetic waves, avoiding the harm of electromagnetic pollution to the human body. It is understood that the current research team of Sejong University in South Korea has completed Korean and international patent applications for this technology and is registering commercial entities for commercial development. Q: Is Air Charging Safe for Health? Is Air Charging Dangerous for Humans? From the previous introduction, it is not difficult to see that wireless charging technology based on light energy does not have health problems . Although magnetic resonance wireless charging technology has radiation, it mainly works at MH or KHz frequency, so it not harmful to the human body. The air charging technology of Xiaomi and Motorola should be based on wireless radio frequency charging technology, and if this technology is to achieve a higher power charging effect for devices at a longer distance, then radiation is naturally a concern for consumers. Calculating Amount of Radiation of Air Charging Some people in the industry have taken the radiation of conventional wireless routers and Xiaomi’s air charging as examples, and made an estimate: The power of a conventional wireless router is generally about 9W～12W, and the transmission power is within 10mW. Since the wireless router transmits in all directions at the same time, in a radius of two meters, its radiation area is about 4 x 3.14 x 200 x 200 square centimeters. Assuming that the area of the mobile phone is 40 square centimeters, Xiaomi’s 5W power is all directed on this 40 square centimeter surface. The ratio of the power density of the body to the conventional router and the Xiaomi air charging transmitter is about 0.01/5 x 40 square centimeters/(4×3.14x200x200) square centimeters=0.00000016. After conversion, the radiation of Xiaomi charging to the human body near the location of the smartphone maybe 6.25 million times that of the conventional Wi-Fi router. Obviously, if there is no problem with the estimated data, then Xiaomi’s air charging technology may have radiation problems. However, it is worth mentioning that the aforementioned GuRu, which also uses millimeter waves to achieve air-to-air charging, once questioned the radiation problem and said: These waves are non-ionizing and can pass through the human body without any harmful effects. And the millimeter-wave used for wireless charging does not have that high power, so there is no need to worry too much about it. “In addition, the “safety and smart” system can automatically detect the correct power level of the equipment and adjust its power usage. Motorola’s space charging technology does not give specific data, so the specific radiation situation is unknown. However, according to Chen Jin, general manager of Lenovo Phone China, Motorola’s demonstration video will stop charging when the charger is blocked by the hand. This is a safety setting specially developed for the user’s health. It mainly integrates the sensing device at the transmitter with a higher power to provide safety protection when the human body is detected. This is the common sense of human-machine protection in engineering design. Obviously, from Chen Jin’s words, we can see that the transmitting end of Motorola’s air charging technology is not unable to achieve air charging under shielding, but because of the radiation problem at the transmitting end, a sensor is specially added. It stops working when the human body is detected. In short: Xiaomi Air Charging Technology could be harmful to health Motorola’s Air Charging Technology is not harmful to health If a brand uses Air Charging based on Radio Wave Technology and the transmission power is high, it can be dangerous for human health. Light Energy Charging Technology isn’t harmful if it isn’t penetrable (Motorola) and harmful if penetrable (Xiaomi) Here’s the summary of the three types of Air Charging: Types of Air ChargingRange/DistancePowerSafe for Human HealthBrands Working Magnetic resonance ChargingShort range0 to 60WYes, if in limit and not penetrableIntel, WiTricity, uBeam, Bose, Huawei, SprouTIng, Ningbo Weie, Shanghai Chushan, Zixiao Technology, Zhonghui Chuangzhi, Taiwan Jiejia Radio Wave ChargingShort to medium range (currently up to 4.5 meters)2W (currently)Yes, if in low transmission limit and not penetrableEnergous, Ossia, Powercast, GuRu Wireless, Vivo, Xiaomi, Motorola Light Energy ChargingLong range (currently from 9 meters to 10 kilometers) 10W (currently)YesLaser Motive, Wi Charge Wireless Charging Patent Statistics According to statistics from IPlytics, since 2010, the number of patent applications for wireless charging of smartphones has continued to grow rapidly worldwide. Especially in 2019, the number of patent applications for smartphone wireless charging increased by 1569 compared with 2018, reaching 5874. From 2010 to 2020, from 2010 to 2020, here are the rankings: 1st: Samsung – 523 patents 2nd: Qualcomm – 484 patents 3rd: LG Electronics – 226 patents 4th: LG Innotek – 209 patents 5th: Apple – 191 patents Huawei and ZTE ranked 10th and 17th with 80 and 53 patents respectively. In short, South Korean and American companies have the most patents in the field of wireless charging, and the only Chinese manufacturers are Huawei and ZTE. Although most of the head manufacturers are smartphone manufacturers or SoC manufacturers, there are also wireless charging technology manufacturers (such as WiTricity, Powermat, etc.) and automobile manufacturers (such as Hyundai, Kia, Ford, etc.). Air Charging Phones List Currently, there’s no phone which features the Air Charging technology. We will add phones to the list once they are official. As for the rumors, here’s the listing: Motorolla Edge (2021) Xiaomi Mi 11 Ultra / Xiaomi Mi 12 Ultra OPPO Find X3 Pro / OPPO Ace 2 Samsung Galaxy Fold (2021) I hope that now you can fully understand what is air charging? Need to know anything? Hit us in the comments section. FAQs Is Air Charging Safe For Human Health? Air Charging technology based on light energy does not have health problems. Although magnetic resonance air charging technology has radiation, it mainly works at MH or KHz frequency, so it not harmful to human health. Lastly, wireless radio frequency charging technology is also safe but if it achieves a higher power charging effect for devices at a longer distance, then radiation is not safe to human health. What is Air Charging in Smartphones? According to Xiaomi’s official introduction, the core of Xiaomi’s air charging technology lies in space positioning and air energy transmission. Its self-developed aerial charging pile (transmitting end) has built-in 5 phase interference antennas, which can perform millisecond spatial positioning of the smartphone, accurately detect the position of the smartphone (receiving end), and then use a phase control array composed of 144 antennas to pass the beam and transmit millimeter waves to the smartphone in a directional path achieving air-to-air charging. Air Charging vs Conventional Magnetic Charging The difference in air charging vs wireless charging is that traditional wireless charging smartphone has a built-in coil that comes in contact with the charging base to charge. Air charging smartphones have a built-in “beacon antenna” and “receiving antenna array” which receive power via air energy transmission from the receiver.