More Reliable Wireless Connections Passive Surface Protects Against Interference From Multipath Propagation

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A research team from the Nagoya Institute of Technology has introduced a novel metasurface that can effectively suppress radio interference from multipath propagation without active components or external energy sources.

As the frequency and density of networks increase, a well-known problem in high-frequency technology grows: multipath propagation. In this case, radio signals reach the receiver not only directly but also via reflections and scatterings, which can lead to superpositions, distortions, or dropouts.

To tackle this challenge, researchers from the Nagoya Institute of Technology, together with Osaka University and Kyoto University, developed a novel solution. Their work, published in Physical Review Letters, describes a passive metasurface that can distinguish between the first incoming signal and later disturbances—without active control and without additional energy input.

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Time-Varying Structure Instead of Complex Electronics

Classic approaches to suppress multipath effects rely on complex adaptive antenna systems or computationally intensive signal processing. Both typically require a lot of energy and hardware. The Japanese team is taking a different approach: they use a passively operating metasurface whose properties dynamically change, triggered solely by the arrival of the first radio signal.

This is made possible by special semiconductor components, specifically MOSFETs, which are integrated into each unit of the metasurface. When radio signals hit the surface, the MOSFETs act like switches: the first signal ensures that the resonance properties of the surface are maintained, allowing undisturbed reception. At the same time, it changes the configuration of neighboring areas so that subsequent signals, which arrive delayed or from other directions, are effectively blocked.

Initial Trials Show Significant Signal Improvement

In an experimental setup, the researchers used a hexagonal prism, with each face equipped with the metastructure. Multiple transmitters emitted signals with slight time delays onto the structure, similar to reflections from buildings or walls. The results show that the first signal was received about 10 decibels stronger compared to the subsequent ones. This effectively filtered out later disturbances—without any external energy sources or complex control algorithms.

The approach could be particularly relevant for IoT devices, which do not allow for complex signal processing due to limited energy and computing resources. It also opens up new possibilities in the field of cost-effective sensors or compact communication modules.

Perspectives for Future Wireless Systems

While the current demonstration model is based on relatively simple components, the developers see potential for significant performance enhancements. Optimized semiconductor technologies and improved arrangements could achieve even higher suppression rates.

Moreover, the method is not limited to radio communication. The time-varying metasurface could also be used in other electromagnetic applications, such as sensors, imaging methods, or novel intelligent surfaces. In an increasingly connected world, this technology could help make radio connections more robust and reliable—without the complexity and energy requirements of previous solutions. (mc)

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