Broadband Microwave Absorption by Logarithmic Spiral Metasurface

Abstract

Metamaterials have enabled the design of electromagnetic wave absorbers with unprecedented performance. Conventional metamaterial absorbers usually employ multiple structure components in one unit cell to achieve broadband absorption. Here, a simple metasurface microwave absorber is proposed that has one metal-backed logarithmic spiral resonator as the unit cell. It can absorb >95% of normally incident microwave energy within the frequency range of 6 GHz–37 GHz as a result of the scale invariant geometry and the Fabry-Perot-type resonances of the resonator. The thickness of the metasurface is 5 mm and approaches the Rozanov limit of an optimal absorber. The physics underlying the broadband absorption is discussed. A comparison with Archimedean spiral metasurface is conducted to uncover the crucial role of scale invariance. The study opens a new direction of electromagnetic wave absorption by employing the scale invariance of Maxwell equations and may also be applied to the absorption of other classical waves such as sound.

Anti-reflecting metasurface for broadband polarization independent absorption at Ku band frequencies

“…Metasurface absorber comprising of complicated geometry build over split ring patch achieves negative refractive index that leads to near perfect absorption at discrete frequencies around X and Ku bands 26 . The logarithmic spiral resonator embedded with lossy materials are used to absorb incident microwave energy between 6 and 37 GHz frequencies 27 . Similarly, the ultrabroadband of microwave radiation were absorbed by metamaterial array of conical shaped saline water columns 28 .…”

Frequency‐independent Sound Absorbing Metamaterials

“…This invariance can be approximately maintained in materials with weak dispersion, as demonstrated in the microwave region. [ 54 ]…”

“…This invariance can be approximately maintained in materials with weak dispersion, as demonstrated in the microwave region. [54] A theoretical acoustic analogy of frequency-independent antennas for sound absorption can be achieved by considering sound waves propagating in an infinite tapered waveguide where reflection diminishes as the velocity approaches zero. Furthermore, porous materials with a significant thickness can be used to achieve near-perfect absorption beyond the Biot frequency.…”

Highly efficient wavefront control based on extremely anisotropic materials

“…Our design strategy is a general method to design metasurfaces and can be extended to other frequency band and other wave systems, and the designed metasurfaces have potential applications in lots of aspects, such as telecommunications, diagnostics, measurements and so on. For example, when the metasurfaces are designed in microwave band, it can be utilized as absorbers [38], and when the metasurfaces are extended to acoustic systems, it could be used for ultrasonic detection [39]. It should be noted that although we realized efficiently wavefront manipulation by the proposed method, it still exists limitations.…”