Consumers are expecting more from their devices—and an always-charged battery, thanks to radio frequency (RF) wireless charging, can make it happen.
The world changes fast. Not so long ago, almost every device was wired — telephones, TVs, computers. We were hooked to wires everywhere. But these days, thanks to the rise of mobile technology, we’re far less dependent on wires. We have all sorts of devices that are wireless.
Well, almost. When it’s time to charge those devices, we’re back to the wires, walking over to the power outlet to plug in and recharge. And wherever your personal charging station is a desk, a counter, a corner of the floor, the odds are good there’s a tangle of chargers and wires.
And this charging snarl isn’t limited to mobile devices. It extends to the world of IoT and intelligent sensors because these connected devices don’t work if they run out of power. Take Amazon Go, the growing chain of Amazon convenience stores where you simply swipe your phone on a scanner when you enter, get what you want, then leave. They use IoT sensors to know what you got and bill you later. That’s great. But those IoT devices have batteries that need to be constantly charged or replaced, which is unwieldy and not ideal.
The good news is that inductive-based technologies are removing wires from the charging process and eliminating the hassle of plugging in devices and replacing batteries. You’ve probably seen those wireless charging pads. Maybe you have one at home. You put your phone on the pad and it charges while it sits there, no wire required.
But, as wireless charging arrives and grows in popularity, a second-generation technology will be needed to support multiple-device charging, freedom of placement, and, most importantly, wireless power delivery at a distance. Imagine: you walk into your living room and your smartwatch starts charging instantly and automatically. That’s the beauty of over-the-air charging.
Here are five big breakthroughs that are enabling this emerging technology to transform the way consumers and industries wirelessly charge and power electronic devices at home, in the office, in the car, and beyond.
Greater distance. If over-the-air charging is to go mainstream, we need to expand the distance at which devices can be charged. This is already happening on a gradual basis. The first step is to deploy the technology in products that adhere to a distance of one meter, and then gradually increase distance.
In fact, my company recently received FCC clearance to develop and market wireless charging products that work within one meter of a transmitter using low-cost, non-beamforming technology. This is the first time that a non-beamforming transmitter has been permitted under the FCC’s Part 18 rules with a conducted power of 5.5W and a charging zone of up to one meter. And, we continue to break new barriers. As an example, the key concept of Part 18 localized power at short distances had to be extended and explained to cover the one-meter distance scenarios as demonstrated with System E-field values up to 16 V/m at 1 meter distance guaranteeing safe WTP transmission.
A good analogy on how wireless power transfer (WPT) technology evolves is Wi-Fi. At first, Wi-Fi routers could only cast their signal reliably at about a foot or two. You had to be right next to them to get online. But gradually, that distance expanded as the technology matured and higher conducted power levels and higher sensitivity receiver performance were allowed, as per Part 15 regulations and IEEE standards. Over-the-air charging will follow a similar path. It’s only a matter of time before over-the-air chargers will be delivering power to devices at a distance of many feet. While the distance has been constrained in the U.S., some large markets already allow for greater wireless charging distances.
Multiple form factors. Wireless charging technology can be embedded into a variety of form factors, with varying technical options. This can include a small, low-cost transmitter to replace the USB cables and power adaptors.
What’s more, over-the-air wireless charging can support a broad range of devices, including small, low-power devices like hearing aids, fitness bands, sensors, and similar devices. This is an important breakthrough because connecting a charging cord to small form factor devices or replacing miniature batteries can be expensive and frustrating.
It’s also important to note that multiple form factors can be supported — not just due to the small size of the WPT technologies —but also because of the advancement and innovation in designing and developing WPT antennas that can now be made an easily integrated part of many devices.
Regulatory support. The next breakthrough is already happening on the regulatory front. The FCC has signaled support for the vision of over-the-air charging. “I believe that wireless power may be vital to the success of future connectivity and productivity,” stated Michael O’Rielly, former FCC commissioner, at a January 15, 2020 hearing before the United States Senate Committee on Commerce, Science, and Transportation.
Currently, a formal Notice of Proposed Rulemaking (NPRM) is being studied by the FCC to define the rules by which WPT will open up and operate in the U.S. Similarly, efforts in the International Telecommunication Union (ITU) to develop WPT rules are well underway. Both efforts indicate the necessity and direction to open up WPT. Simultaneously, multiple countries have national efforts supporting WPT. As an example, Japan has the Broadband Wireless Forum (BWF) focusing on WPT.
Enhanced safety. The ability to deliver power to devices at a distance safely is, obviously, vital. Over the past 10 years, there have been great energy consumption improvements in computing power, storage, and wireless connectivity. We’ll soon see the same step-function improvements in low-power consumer devices, including potentially increased computer performance and higher communication link power efficiency leading to smaller and smaller batteries that require to store less energy.
As devices use less power, the amount of wireless power you need to transmit to charge these devices is also reduced. So, it becomes much easier to safely deliver power to devices over the air without causing harm to humans, by keeping the energy levels within a well-established specific absorption rate (SAR) of less than 1.6 W/Kg in the USA and 2.0 W/Kg in other countries, and E-field levels. In fact, the FCC has now approved multiple wireless transmission devices at or above 5.5W of conducted power within a one-meter distance for a WPT system, as compared to Wi-Fi Access Points which are limited to 1W of conducted power.
Lower cost and higher performance. Thanks to increased power efficiency, optimized architectures, and advanced WPT innovations the cost of implementing wireless-charging technology is declining dramatically, which should lead to mass adoption. And by using the latest semiconductor processes, along with cutting-edge CAD tools developed for RF communication systems (chip, antenna, etc.), it is possible to use these advances to propel WPT toward early technology maturity and take advantage of the cost structure available to high volume consumer devices.
For instance, matured complementary metal–oxide–semiconductor (CMOS) processes are used in the control section architecture of the WPT transmitters and receivers to lower the system power consumption overhead. Meanwhile, GAN and GaAs processes are used in the design of highly efficient power amplifiers and rectifiers, which easily outperform CMOS power efficiencies by greater than 30%, and are designed to support higher power devices at high output powers > 1 Watt into the 10s of Watts to increase the system power overhead transfer efficiency.
All of the above-mentioned breakthroughs are near at hand. The final piece of the puzzle will be standardization. Companies in the industry must coalesce around a common over-the-air charging standard and must come together to form an ecosystem around that standard, just as Qi has become the accepted standard for wireless power transfers using inductive charging over short distances.
Standards are essential for interoperability, of course, but they also help drive down costs. This means that a standard for wireless power will make it even more attractive in the eyes of device manufacturers — and should lead to greater technological innovations down the road.
Over-the-air wireless charging is not a “nice to have,” it is increasingly becoming a “need to have.” Every year, consumers expect more and more from their devices — and an always-charged battery is at the top of their list of expectations. Radio frequency (RF) wireless charging will make it happen.
This article was originally published on EE Times.
Cesar Johnston is the chief operating officer and executive vice president of engineering, Energous Corporation.