Fractal Metamaterial Surfaces for UHF Sensing Applications

Abstract

A dual-band fractal metamaterial absorber is proposed as a promising alternative for sensing applications. A preliminary prototype, useful to validate the proposed configuration, is designed to operate in the Ultra-High Frequency (UHF) range. The inherent miniaturization skills of fractal geometries are effectively exploited to design and fabricate multiband/broadband absorbers with a small lattice size ( $\le \lambda _{0}$ /2 at the smaller operating frequency $f_{0}$ ) and a very thin profile ( $\le \lambda _{0}$ /100). Two pairs of Minkowski fractal patches, alternately arranged in four different quadrants and properly sized to achieve two distinct absorption peaks, are assumed for the absorber-sensor configuration. In the framework of dielectric material diagnostics, the MA structure shows an average relative sensitivity of 4.6% and a quality factor equal to 36. Very high absorption peaks (>99%) and quite good stable absorption rates versus incidence angle variations ( $\ge 90$ % for TE polarization and $\ge 97$ % for TM polarization at both frequencies) are demonstrated both numerically and through experimental validations, thus proving the applicability of the proposed absorber sensor in low-frequency sensing applications.

Keywords

• Dual-band
• fractals
• metamaterial absorbers
• microwave sensors