Xiaomi Mi Air Charge: charge the Smartphone by holding it in your hand

February 28, 2021 Savior

What is Xiaomi Mi Air Charge?

Imagine a future in which you come home in the evening, sit on your nice sofa in the living room, your smartphone is completely empty but you would like to continue using it without constraints, charging it simply by holding it in your hand and without having to connect it to the charging cable or place it on a Wireless charging base. Impossible? No! Mi Air Charge is the technology that will allow all this . The Chinese company's goal is to allow real wireless charging of devices (Smartphone, Tablet, Smartwatch) without any type of constraint (wire or charging base) up to several meters away. Furthermore, according to what has been revealed so far, it would be possible to recharge multiple devices in the same room.

How does this technology work?

Let's now analyze how this technology works. So far we are used to using induction wireless recharges, i.e. those recharges that require physical contact between the Smartphone and the charging base . What happens in Induction type charging is that the transmitting coil (located in the charging base) generates an outgoing magnetic field. If the smartphone is brought close to the transmitting coil (it must be at distances d <8 mm) an induced current will be generated in the receiving coil . The physical principle underlying this technology is precisely electromagnetic induction .

*Difference between induction and resonance wireless charging Source: belkin.com*

*Induction charging example Source: belkin.com*

The wireless resonance technology developed by Xiaomi is based, on the other hand, on sending millimeter electromagnetic waves towards the antennas of our smartphone. We have an "isolated charging battery" which contains 5 Phase Interference Antennas to accurately detect the position of the Smartphone in the room . Furthermore, through the Beamforming technique, the 144 antennas on the battery will transmit millimeter waves for recharging. The Beamforming technique is already used in many Wi-Fi Routers and allows you to direct and concentrate the electromagnetic signal in one direction rather than another . To give a simple example, suppose we throw a stone into a lake: the impact between the stone and the water we obviously know that it generates concentric mechanical waves.

This is exactly what happens with a Wi-Fi type signal without Beamforming technique: the electromagnetic waves are sent concentrically with respect to the source . This method generates a signal that guarantees as much coverage as possible, but also causes a loss of energy in places where there are no receiving devices . Through the Beamforming it is possible to modulate the amplitude and phase of the signal to ensure greater power in the directions along which the receiving devices are located, so as to have a better distribution of the useful band .

*Difference between traditional Router and Router with Beamforming technology Source: fastweb.it*

Analyzing the technology of Xiaomi on the Smartphone side, we have 1 Beacon antenna and a miniaturized antenna array to receive millimeter waves. The Beacon antenna allows the low-energy detection of the Smartphone in space . This uses low power and other frequency BLE (Bluetooth Low Energy) type signals. The array of antennas in the Smartphone, on the other hand, allows to capture millimeter waves to send them to a Rectifier circuit which will convert it into electricity for the battery. As for the current Xiaomi statements, this type of recharge allows powers of 5 W, the possibility of recharging multiple devices at the same time and with the same efficiency even in the presence of obstacles.

When will it be available?

Xiaomi has not yet released statements on possible Mi Air Charge release dates , but we know that it is still a technology that needs to be worked on. However, we can already imagine that these devices will be in all our living rooms, they will allow the use of completely wireless sound bars, lamps and devices for the Smart Home. If you are interested you can watch the official video released by Xiaomi which also provides a visual idea of how it works.