Negative Index Metamaterial Based Dual-Band Microwave Absorber

摘要

This paper presents the design of a dual band metamaterial microwave absorber using a spider like resonating structure obtained by diagonally interconnecting half cut square rings with square pads added at the open ends. Multiple resonance has been reduced to two resonating frequencies of 5.38 GHz (C band) and 9.09 GHz (X band) with 98.8% and 99.8% absorption respectively through a split in the middle of the structure. The structure is built on the top layer of FR4 dielectric substrate with a metallic ground plane at the bottom layer. The dual band absorber is characterized at various oblique incident angle and at different polarization angle for normal incidence. C band peak exhibits polarization independent performance for 0° to 45° polarization angle while the second X band peak shows polarization independency for 0° to 90°. The current distribution over the structure at the tuning frequency is presented to understand the working of the structure. The metamaterial behavior of the structure is verified with the negative permittivity and permeability parameters derived from the S parameters at the resonating frequency. The designed structure is unique without closed ring structures and exhibits both polarization independent and polarization dependent absorption on one metamaterial structure.