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Coating makes EM waves see curved surfaces as flat

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A new technique that allows curved surfaces to appear flat to electromagnetic waves has been developed by scientists at Queen Mary University of London.

According to QMU, the discovery represents a potential a step-change in how antennas are tailored to each platform, benefiting industries that rely on high performance antennas for wireless communications.

The researchers coated a curved surface with a medium where the refractive index varies depending on the position of the wave. Although the coating is only a fraction of a wavelength thick, it can make the curvature appear invisible to surface waves.

The coating can be used as a so-called cloak because the space created underneath the bumpy surface can shelter an object that would ordinarily have caused the wave to be scattered.

In a statement, Professor of Antennas and Electromagnetics and study lead Yang Hao, said: ‘The design is based upon transformation optics, a concept behind the idea of the invisibility cloak. While the cloak is yet to be demonstrated ‘perfect’ in the free space, we have proved that it is possible for surface waves.’

The underlying theory developed in this study has had a wide impact on the antennas and aerospace industry.

‘With the demands of telecommunications systems in airborne and ground-based vehicles growing year by year, it is necessary to create antennas with ever increasing efficiency, yet keeping the weight and volume as low as possible,’ said co-author Dr Rhiannon Mitchell-Thomas from Queen Mary’s School of Electronic Engineering and Computer Science

‘When electromagnetic waves encounter a bump in the surface, this alters their characteristics and decreases the efficiency of the antenna. Using this new technique, a bespoke surface wave antenna can be designed to fit the precise shape of the platform.’

Co-author Oscar Quevedo-Teruel also from Queen Mary’s School of Electronic Engineering and Computer Science added: ‘This type of integrated antenna system can be applied for any frequency band from microwave to optics, leading to ultra-fast wireless communication over the surface in the near future.’

The EPSRC-funded project was published on November 20, 2013 in Physical Review Letters.