Ultra-broadband 3D Metamaterial Microwave Absorber Based on Split-Ring Structure Loaded with Resistors and Magnetic Material

In this paper, an ultra-broadband three-dimensional metamaterial microwave absorber (MMA) is proposed based on a composite structure of a split-ring loaded with resistors and magnetic material. The proposed composite MMA (CMMA) exhibits significantly enhanced bandwidth and absorption performance compared to single magnetic absorbing materials. The physics mechanism of the absorption is analyzed by the distributions of electric field, magnetic field, and power flow and loss density. The features of ultra-broadband and wide-angle absorption were systematically characterized by the angular absorption spectrum for both transverse electric and transverse magnetic waves. A parametric study was also performed to achieve ultra-broadband properties of the proposed CMMA. A tested prototype of the proposed CMMA with 18 x 18 unit cells was fabricated and measured. The final experimental results show that the designed CMMA with total thickness of 7.4 mm exhibits absorptance of over 90% from 3.7 GHz to 18 GHz with a relative bandwidth of about 131.8%, which is in good agreement with simulation results. The proposed CMMA has potential applications in stealth, shielding, and energy harvesting.