Broadband and Polar-insensitive Radar Cross Section Reduction of a Cylindrical Target on the Conformal Frequency Selective Surface with Resistors

Frequency Selective Surface (FSS), as a typical electromagnetic absorber, is widely investigated in research works because of its flexible design and excellent absorbing performance. However, there is no care taken about the resulting scattering pattern from a certain engineering target coated FSS absorbers. In this paper, we proposed a novel conformal FSS absorber with resistors by suppressing specular scattering from the cylindrical target, to achieve a broadband and polar-insensitive radar cross section (RCS) reduction. The conformal FSS absorber from top to bottom is made up of a dielectric FR4 layer, an FSS layer, a honeycomb spacer and the cylindrical metal surface. The FSS unit is a metallic square with a concentric circle subtracted in the center. And the inserted resistors are used to transform the incident electromagnetic energy into heat. To obtain a broadband and polar-insensitive RCS reduction, the trade-off with a specified target and the absorbing performance of the FSS-based absorber is extremely important. Thus, we carried on multiple optimizations by the FDTD method, and applied the conformal FSS absorber to the area, where specular scattering is the primary scattering mechanism affected the RCS value of the cylinder. Compared to the same size PEC cylinder, the simulation results demonstrate that an 80% RCS reduction is obtained over a wide frequency band ranging from 2.9 to 12.8 GHz for both HH and VV polarizations at normal incidence, and a 90% RCS reduction at 2.9-6.0 GHz and 8.4-12.5 GHz. According to the above, we think that the ideal of the conformal FSS absorber design is applicable to other frequency bands and a wide-incident angle applied in EM stealth technology.