Ultra-wide-angle and broadband metamaterial absorber based on monopole top loading antenna and its reciprocity

In this paper, an ultra-wide-angle and broadband metamaterial absorber with a monopole top loading structure (MA-MTLS) was proposed. The resistive films printed on the dielectric are on the top layer. The dielectric square cylindrical shells with resistive films on the outside are in the middle, and a metal plate is on the bottom layer. The whole structure can be regarded as a top loading monopole antenna that has a good omnidirectional radiation capability. According to reciprocity, when a composite structure is used as an absorber, it will have a good absorption performance. The impedance matching characteristics were demonstrated by Smith chart and equivalent circuit, and then, the absorption performance was optimized. The simulated results show that the absorption of the MA-MTLS is more than 90% under TM polarized waves of 3.6–13.8 GHz as the incident angle changes from 0° to 80°. When the incident angle increases to 83°, the absorption is higher than 80% in the frequency band of 3.7–14.5 GHz. At the stage of experiment, the dielectric substrate was made by three-dimensional printing technology, the resistive films on the top layer were printed using screen printing techniques, and the resistive films on the outside of the square cylindrical shells were completed by pasting. The consistency between the experimental results and simulation data indicates that the design method is feasible and has good application prospects.