Because a new method of using multi-antenna is born, wireless charging of Internet accessories (and even smartphones) is turning into reality. To this end, HUIB Visser, senior researcher in the Netherlands, made a brief introduction to the current status and future development.
You may say that because the inductive charger has been launched for a long time, "the wireless charging of smartphones has become possible." Of course, this is not completely incorrect, but "no connection charging" may be more suitable for describing today's technology, because induction charging still needs to maintain close contact between the charging station and its devices. This not only limits its use on smartphones, but also makes the current method and will be incompatible with the requirements of the Internet of Things devices that are increasingly flooded.
Thanks to the development of 5G, industrial 4.0, smart cities, intelligent transportation, and we will see the growth of battery drive equipment. It is impossible to charge through wired or short-range sensing. Instead, they need to get energy from the surrounding environment. Especially in indoor applications, while other methods, such as photovoltaic or thermal transmission quickly reach limitations, so that wireless charging is a good candidate.
Real wireless charging means to some extent: long-distance transmission sufficient electrical energy without aiming directly to a mobile device and a fixed device. So far, there is no technology to enter the market and meet any of the above specifications. However, IMEC has recently had a new technological breakthrough, people can start dreaming a less distant future, all of which may become a reality.
Restricted by physical law and government
As mentioned in his blog "DREAMING OF POWER THROUGH THE AIR", the Wireless Power Alliance Chairman Menno Treffers may be one of the most important factors that have long exposed to RF electromagnetic fields may be one of the most important factors that have not yet entered the market. The law of physics suggests that in the electromagnetic wave of spherical expansion, the power density is decremented twice as the distance. For ultra-low power equipment, it is still possible to generate sufficient electrical energy at a few meters away from the charging station. Therefore, for this specific condition, a business solution is already available. Therefore, it is easy to improve the distance of sufficient power.
The first experimental results prove the long-distance power supply capacity of the Internet of Things sensors.
IMEC has built a demonstrator in 2018, a continuous power of 25 microves (1,5 or 3V) in 5 meters away from the 3 watt EIRP transmitter (EIRP is the product of transmit power and antenna gain) Budget. This is an improvement in two to three times as compared to commercial equipment, and such power energy can be obtained at a distance.
By storing these energy in the condenser, it is possible to release dozens of milliwatts in a few microcodes every two minutes. This is enough to wake up a radio, activate a sensor to measure some data and transfer the data wirelessly to the receiver. IMEC demonstrates a scene in the 915MHz and 245GHz band, which is two free-license bands of the United States and worldwide, scientific and medical (ISM), respectively.
In order to obtain these results, IMEC established two special RecTenna prototypes to ensure power conversion at the receiving end. For these prototypes, IMEC uses a non-conventional method for system optimization. IMEC does not separately optimize each module (rectifier, converter, power management circuit ...), but is selected for sub-opticizing antenna: provide relatively high DC voltage, but create an opening in the available power envelope, Further optimize the power management circuit. This leads to better overall system performance than alone to optimize each build block.
Two Rectenna prototypes for electrical energy conversion in wireless charging devices
Two RecTenna prototypes are used in electrical energy conversion in the wireless charging device. One for 915MHz US-ISM band (left) and a global 2.45 GHz ISM band (right). Both RecTennas have a miniaturized antenna integrated on the PCB. 2.45 GHz Rectenna is integrated on a metal housing by a ground shielding device.
Although it is sufficient for the Internet of Things sensors, the realized power output is far less than a device such as smart phones. And in the recipient, there is almost nothing available. To get the power density required for charging of high power devices, the transmitter must be raised to legal unacceptable levels.
Multi-antenna settings to overcome the power limit for larger distances
By combining the transmitter strength of the plurality of antennas, in the case where no radiation limit is not more than any radiation limit, a power density is sufficiently high. Smaller spherical bubbles.
By using a triangular concept having multiple antennas (top), high-power bubbles (right figures) can be created without exceeding any statutory radiation limit. Figure Left: A classic spherical broadcast antenna pattern. Intermediate map: A directional antenna is conducting research in 5G scenes, but its applicability in the ISM band is still limited.
In this case, all antennas can be launched at the maximum power allowed by law, but the emission time interval is different. The resulting spherical electromagnetic waves will be propagated independently of each other (and subjected to secondary power attenuation). By smart design time interval, we can create a focus to bring these waves together. In this focus area, the energy density is superimposed to each other, forming a higher energy density air bubble, can be placed on a battery-powered device that requires rechargeable.
For N antenna array, the average power gain is N, and the peak power is N × 2. That is to say, there are two antennas, your average power is doubled, and the peak power is increased by four times. This is a more advanced method that is more advanced than the intelligent antenna scene being studied in the 5G environment. These use oriented beams, but are still subject to legal power to ISM bands.
From seeing can't see, from fixed to mobile
With this method, IMEC conducted a series of successful experiments. In the case of non-optimized settings, non-ideal pulses and a large amount of scattering, these tests confirm the theoretical power gain - can be generated at the designated position by adjusting the time interval - power bubbles. It is very hope that this setting is large due to its significant simplicity, and the antenna is relatively away, and the position of the object is fixed and is known in advance.
Now, IMEC will raise the entire concept to a new level; this technology is also applying for patents. The ongoing studies include placing the antenna closer location (so they can be part of the same base station), and the object does not have to be within direct line. By analyzing the scattering and reflection of the transmitter signal returns the base station, we can find a method of charging the device, even if they are at the corner, or if an object is a direct path between the transmitter and the receiver. Once this approach passes, this feature will become an important asset that realizes the real application, one of which can be charged in the same room as a plurality of (IoT) devices without being obstructed by other objects nearby.
In order to further develop, IMEC is developing a method of passive position detection of a device that needs to be charged. Even if the battery of the receiving device is empty, the signal from the base station can still retrieve the location of the device and start charging. This solution is especially important in the scene of smartphone charging, because no one really wants to put the smartphone in the same place every time it is charging.
For the Internet of Things devices, this feature may not be so important, because most Internet sensors will be installed in a fixed place (such as the air quality sensor installed on the wall), or may return to a Know the location (such as sensor industrial robots, returning to his alternate location after each operation). However, for the Internet of Things sensors, the potential advantage of position detection is not underestimated. Power limit is one of the most stringent specifications in the IoT system design. In particular, battery-driven sensors need to have several years of autonomy in the case of charge. This means that the amount of data that can be transmitted must be maintained at a minimum, not to mention the strict limitations of calculating intelligence that can be embedded in such sensors.
If the passive position detection allows the charging station to detect and give the Internet of Things sensors that are not fixed positions to charge. This will greatly increase the available power budget, thereby increasing the intelligence levels that can be embedded.
IMEC is currently experimental settings and is actively looking for industry partners, hoping to develop these concepts and technologies, these concepts and technologies can be transferred to industry solution providers.
Our other product:
