A miniaturized low-frequency polarization-insensitive metamaterial absorber based on broadside-coupled spiral structures

In this paper, we present the design, simulation, and experimental demonstration of a miniaturized low-frequency metamaterial absorber based on the broadside-coupled spiral structures. The tested results indicate that the metamaterial absorber can achieve a miniaturized narrowband absorption with a peak absorption of 98% at 1.39 GHz. Both of the unit cell size and the total thickness of the metamaterial absorber are 6.8 mm that is approximately 1/32 of the working wavelength. Since the spiral structures of the metamaterial absorber are arranged in rotational symmetry, the absorber is polarization-insensitive to the normal incident electromagnetic wave. Additionally, the metamaterial absorber can strongly absorb the obliquely incident electromagnetic wave for both transverse electric and transverse magnetic polarizations, even at 60 degrees angle of incidence.