A Frequency Selective Absorber With Anisotropic Reflection Band for Radar Cross Section Reduction

In this paper, a frequency selective absorber (FSA) with an anisotropic reflection band is proposed for radar cross Section (RCS) reduction applications. The presented design is a 2-D triple-layered structure consisting of a lossy frequency selective surface (FSS) at the top, a lossless FSS at the intermediate, and a metal plane at the bottom. All the layers of the proposed structure are printed on the low-cost FR4 substrate and separated by air spacers. The lossy FSS layer loaded with lumped resistors leads to a wide absorption band. The reflection band with anisotropic property is attained using the intermediate lossless FSS layer, constituted of two intersecting non-perpendicular dipole-shaped patches in each unit cell of the structure. By adjusting the angle between two dipole-shaped patches (
$2\alpha$
), the location of the reflection bands can be tuned across the absorption band. Under the normal incidence, the presented design covers a wide absorption frequency range of 2.4 GHz to 8.3 GHz, where the reflection coefficient is below −10 dB (fractional bandwidth = 110%). Considering
$\alpha $
= 35°, the reflective notch frequencies at
$f_{TE}$
= 4.47 GHz and
$f_{TM}$
= 5.74 GHz are attained under transverse-electric (TE) and transverse-magnetic (TM) polarizations, respectively. To validate the performance of the proposed design, a prototype was fabricated and measured. The results demonstrate good agreement between the measured and simulated data.