Design and Analysis of Electromagnetic wave Absorbers based on Frequency selective surfaces

Abstract

The work presented in this thesis is primarily focused on the novel work on novel frequency selective absorber (FSA) applicable for stealth technology. The preliminary absorber designs were explored by modeling of metamaterial structure.The introductory absorber is simulated as well as optimized by its equivalent circuit structure for the C band. 12*12 octagon elements with parasitic elements comprising of lumped resister have been fabricated on FR4 structure with an air gap. Wider bandwidth is deliberately attained due to maximizing the substrate height via airgap and notched rectangular shape as parasitic elements. The wider bandwidth from 2.84 GHz to 9.12 GHz in TE and TM polarization is an outcome of the proposed structure which can also be verified by the free space measurement technique. The overall unit size of the absorber is 22 * 22 mm2. Miniaturization of and#955;/6.67 in size and and#955;/3.33 in thickness can be optimally used for air-craft, submarines, Radar, satellites characterized as stealth technology. Consequently, a conformal metamaterial absorber with quad band performance as a function of frequency was implemented. This is also being simulated and mathematically synthesized by its equivalent circuit . The proposed structure comprises variable electrical length caused by multiple geographical iterations which were validated by its mathematical formulation. This results in a stronger electrical field at concentric circles for the multiband operation. So proposed structure was working in the quad-band (4.11 GHz, 5.37 GHz, 7.39 GHz, and 8.4 GHz). Thin polyester substrate (0.5 mm) and diversity frequency up to quad-band in the absorber make it appropriate for the flexible absorber. In the final stage, absorber design was analyzed and simulated for the L and S band. Wideband with polarization insensitivity confirm the benefit of the L and S band metamaterial absorber (LSMA). This structure is basically enthused from the interspace capacitance and length-based inductor from the split ring resonator. The optimized