In this paper, a quadruple-band metamaterial polarization-insensitive absorber with low profile is proposed. The proposed unit cell is composed of three conformal modified rings with square patches at corners. 10*10 periodic unit cells constitute the proposed metamaterial absorber. The absorber offers low profile, and overall dimensions are 100 mm*100 mm. The surface current distribution and equivalent circuit model are presented to explain the mechanism. The proposed structure is fabricated, and experiments are carried out to validate the design principle. The simulated and measured results show that the proposed structure exhibites four absorption peaks of 98.87%, 95.11%, 93.97%, and 99.99% under normal incidence at 8.16-8.29 GHz, 10.275-10.38 GHz, 14.255-14.38 GHz, and 15.465-15.7 GHz which cover X- and Ku-bands, respectively. The designed structure is exactly symmetrical which makes it insensitive to polarization angle variations. Furthermore, the four operating bands of the absorber can be adjusted independently which makes the design suitable for absorbing electromagnetic energy and reducing the radar cross-section (RCS) of target.
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