Engineers Tap Excess Wi-Fi Signals to Power Small Electronics
Researchers are using spin-torque oscillators to harvest and convert wireless radio frequencies into energy to power gadgets and sensors.
Engineers from the National University of Singapore (NUS) and Japan’s Tohoku University have developed a technology that can harvest excess Wi-Fi signals to power small electronics. The device is equipped with tiny spin-torque oscillators (STOs), which can tap into Wi-Fi’s 2.4GHz RF band and convert it into energy. Those STOs generate microwaves and are typically used in wireless communication systems but are hindered due to low output power and linewidth. There are methods to overcome that issue, including mutual synchronization of multiple STOs; however this presents other problems, such as spatial restrictions and limited frequency response.
To rectify those issues, the engineers built an array outfitted with eight STOs connected in a series, which allows them to harvest 2.4 GHz electromagnetic radio waves and convert them into a direct voltage signal, that’s then transmitted to a capacitor. During testing, they illuminated a 1.6 V LED for one minute after charging a capacitor for 5-seconds.
The electrical topology for designing on-chip STOs plays an important role, which is affected based on the STOs orientation. The researchers compared a series design with the parallel one and found that the parallel configuration is more suited for wireless transmission due to better time-domain stability, spectral noise behavior, and control over impedance mismatch. Those in a series configuration provide a better advantage for energy harvesting due to the additive effect of the diode voltage from STOs. The team is now looking to increase the number of STOs in their array to increase the device’s energy harvesting capabilities to charge other useful devices and sensors wirelessly. They also want to partner with industries to produce on-chip STOs for self-sustained smart systems.