What is it about?

The underlying physics of the absorber is an electrical dipole resonance, converted into two magnetic dipole resonances through interaction with the image electrical dipole created by a metallic boundary. The magnetic dipole resonances have a high magnetic permeability, so that by adding resistors, one can create a broad frequency regime over which the absorber's impedance is matched to vacuum, thereby leading to zero reflection, or total absorption. A hierarchical structure is then created, that staggers the original structure upon a structure that is 1/4 the scale of the original structure. The hierarchical structure then can absorb over a very broad frequency regime. However, diffraction in the higher frequency regime becomes inevitable. So the microwave absorbing foam is added in the interstitial spaces to absorb an overwhelming fraction of the diffraction energy. The net result is an absorber that can absorb 99% of the microwave energy over the regime of 3 GHz to 30 GHz. This covers all the high frequency bands of the 5G.

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Why is it important?

With the advent of 5G, our absorber and remediate the health concerns of increased microwave power permeating the 5G active space, as well as balance the need for monitoring and privacy.


This microwave absorber stands out by its thin sample thickness (14 mm) that is only 5% over the limit set by the causality principle, as well as the extreme broadband absorption spectrum. The structure is very simple and amenable to mass production at low cost. The underlying physics is also novel--impedance matching to vacuum achieved by electrical dipole resonance interacting with its image, through an electrically conducting interface.

Ping Sheng
Hong Kong University of Science and Technology

Read the Original

This page is a summary of: Conceptual-based design of an ultrabroadband microwave metamaterial absorber, Proceedings of the National Academy of Sciences, September 2021, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2110490118.
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