Fractal Metamaterial Surfaces for UHF Sensing Applications

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.