Exploring microwave absorption by non-periodic metasurfaces

Abstract

In recent years there has been a large body of work investigating periodic metasurface microwave absorbers. However, surprisingly few investigations have focused on the absorption performance of similar non-periodic designs. In this work, the electromagnetic response of a large area (310 mm x 310 mm) microwave absorber that lacks a global periodicity is experimentally studied. The top metallic layer of the ultra-thin (0.3 mm) absorber is structured with rectangular patches given by a procedurally generated non-periodic pattern, known as the toothpick sequence. The specular reflectivity of both p-polarised and s-polarised incident radiation shows coupling to an additional low frequency mode when compared to a standard square patch periodic absorber. To further explore the coupling efficiency of such non-periodic absorbers, finite element models were used to investigate the influence of increasing sample size.

Multi-resonant tessellated anchor-based metasurfaces

“…However, for both polarisations, there is a clear branching of the 10 GHz mode for angles greater than 20°. This is due to the onset of diffraction, which occurs in periodic structures when the size of the unit cell is greater than half the wavelength 22 . The red dotted lines show the predicted diffraction edges (from simple diffraction theory), which correspond to the frequencies above which the onset of diffracted orders results in additional radiative loss channels.…”

“…The specular reflectivity was also measured as a function of elevation ( ) angle (with normal incidence defined as 0°) between 7.5° and 65° from normal (in 5° steps) for both TM and TE polarised radiation, using a Naval Research Laboratory (NRL) arch 22 , shown in Fig. 2 c. The NRL arch consists of two broadband microwave horn antennas, which can independently move around the arch’s circumference to allow full characterisation of the specular reflectivity of the sample.…”

Topological Flexible 3D Microwave Perfect Absorber

“…[19] The absorbing performance of metamaterials can be readily adjusted by tuning their structure parameters, which allows them to surpass the limitations of traditional absorbing materials. [20][21][22][23][24][25][26][27][28] Plenty of metadevices have been developed, such as tunable absorbers, [29] active microwave camouflage, [30] and reconfigurable cloaks. [31] However, processing high-frequency metamaterials including photolithography, electron beam lithography, nanoimprinting, and laser ablation is usually difficult, time-consuming, and costly.…”

Disorder Effects in One-Dimensionally Periodic Extraordinary Transmission Structures

“…Despite the great interest attracted by periodic extraordinary transmitting structures, only limited attention has been paid to aperiodic arrays, i.e., those with arbitrary or even random separations between scatterers (either apertures or metallizations) [20,21] given the difficulty of their modeling [22,23]. For practical applications, local periodicity is assumed, and only smooth variations of geometrical parameters are used to limit aperiodicity effects [24,25].…”