A Planar Compact Absorber for Microwave Sensing Based on Transmission-Line Metamaterials

This work introduces a novel microwave sensor leveraging a perfect metamaterial absorber (PMA) based on transmission-line metamaterials, marking a significant step toward enhancing sensing capabilities. Unique design choices, including the integration of lumped inductors and series capacitors within the unit cell to synthesize a negative and near-zero permittivity, elevate the sensor’s resolution and lower the absorption frequency. These modifications enhance sensitivity and precision for detecting small material quantities, with the sensor achieving an absorption efficiency exceeding 98%. The design also ensures robust performance against changes in incident angles and polarization due to its compact profile, rendering it versatile for diverse sensing applications. Experimental validation confirms the sensor’s performance, highlighting its efficacy in material detection with a notable frequency shift sensitivity of 500 MHz for permittivity changes from 3 to 18, establishing it as a transformative structure for metamaterial-based microwave sensing technologies. Furthermore, the sensor demonstrates a resolution of 5.01 MHz per percentage increase in soil moisture content, offering a new benchmark in the precision of environmental sensing. This breakthrough in design and functionality establishes the sensor as a pivotal tool in the advancement of metamaterial-based microwave sensing technologies, promising widespread applicability, and impact.