A team of engineers at Aalto University has made a groundbreaking advancement in wireless charging technology. Traditionally, wireless charging over long distances has been inefficient, but the researchers have now optimized the interaction between transmitting and receiving antennas by utilizing “radiation suppression.” This approach allows for a much better understanding of wireless power transfer compared to the standard inductive methods.
Typically, short-distance wireless charging through induction pads achieves high efficiency using magnetic near fields. However, as the distance increases, the efficiency drops significantly. The new research, published in Physical Review Applied, reveals that this high efficiency can be maintained over longer distances by suppressing the radiation resistance of loop antennas involved in transmitting and receiving power.
The team had previously developed an omnidirectional wireless charging system, allowing devices to be charged from any orientation. Now, they have taken it further with a dynamic theory of wireless charging that considers both near and far distances and conditions. Remarkably, they found that transfer efficiency above 80% can be achieved at distances approximately five times the size of the antenna, using the optimal frequency within the hundred-megahertz range.
Nam Ha-Van, the lead author and a postdoctoral researcher at Aalto University, explains that they aimed to balance power transfer efficiency with the inevitable radiation loss that occurs over longer distances. By ensuring equal amplitudes and opposite phases in the loop antennas’ currents, they were able to cancel out the radiation loss and enhance efficiency.
The researchers have also developed a comprehensive method to analyze any wireless power transfer system, enabling a thorough evaluation of efficiency at both near and far distances—a novel approach not undertaken before. They tested charging between two loop antennas positioned at a considerable distance relative to their sizes and confirmed that radiation suppression significantly boosts transfer efficiency.
Ha-Van emphasizes the importance of finding the optimal setup for wireless power transfer, regardless of distance. Their approach allows for extending the transfer distance beyond that of conventional wireless charging systems while maintaining high efficiency. This technology has the potential to benefit not only phones and gadgets but also biomedical implants with limited battery capacity. Moreover, the researchers have considered obstacles such as human tissue that might hinder the charging process.
Source: Aalto University