Carriers are rolling out 5G networks across the globe, promising to deliver lightning-fast data to devices of all shapes and sizes. So far, the speed claims of 5G have been little more than smoke and mirrors. However, the architects of 5G technology may have unwittingly provided the key to wireless power. A team at Georgia Tech has developed a small, 3D-printed antenna that can harvest power from 5G waves. This technology has the potential to turn wireless data networks into a wireless power grid.
5G comes in several different flavors, each one with its own advantages and disadvantages. There’s low-band 5G that operates in the range of several hundred megahertz, offering good range but lower speeds. Mid-band signals on the order of a few gigahertz can provide much higher speeds in exchange for a modest reduction in range. Both of those are classified as sub-6GHz; once you get over 6GHz, you’re in the realm of millimeter-wave 5G, going as high as 40GHz in the US. That’s what Verizon and AT&T started with because that spectrum was readily available and very, very fast. The problem? Very little range.
Some past attempts to harvest power from wireless signals have focused on Wi-Fi, which tops out at a few gigahertz like mid-band 5G, but millimeter wave (mmWave) is a whole different story. Millimeter-wave (mmWave) 5G can transmit multiple gigabits per second because of its high frequency and power, and that means there’s more potential energy to harvest. This, too, has been demonstrated, but these demos needed a large rectifying antenna. The larger the antenna, the narrower its field of view, making it impractical for energy harvesting. The tiny cards developed by the Georgia Tech team solve this problem by adding a component called a Rotman lens — the spiky shape in the middle (above).
A 5G millimeter-wave cell site on a light pole in Minneapolis.
Rotman lenses are already widely used in 5G beam-forming applications. They can reshape a single narrow beam into multiple simultaneous beams covering a wider area. That’s why the Georgia Tech antenna is so tiny and efficient — it pulls in 21 times more power than a standard rectifying antenna of the same size.
However, we’re still not talking about a huge amount of power. The high-frequency mmWave signal generates about 6 microwatts of power at 180 meters (590 feet) from a 5G transmitter. That’s also with unobstructed line-of-sight; mmWave signals are too high-frequency to pass through walls, but that’s also what makes them easier to harness for wireless power.
A few microwatts is still enough to power sensors and simple IoT gadgets, eliminating the need for batteries. The team believes that wireless power could become a transformative 5G technology, but that’s probably only true if carriers figure out how to charge for it.
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