Frequency-Selective Absorbers

Absorbing Low RCS Ground Plane 3D Model
Absorbing Low RCS Ground Plane 3D Model

Narrowband and broadband absorbers serve many purposes. Highly-selective absorbers can help to mitigate specific sources of interference, while broadband absorbers can be used to help reduce radar visibility. Periodic, tiled structures can be used to create highly-efficient absorbing coatings and layers that do not rely on bulky, heavy materials. In many cases, by pursuing metamaterial- or AMC-inspired devices to control the fields within a periodic structure, very high absorption factors can be achieved.

The PFEBI solver was used to optimize an FSS screen that acts as a highly-reflective ground plane for an antenna at low frequencies, but as an absorber at high frequencies. This thin structure (7.14mm for a 1.4 GHz antenna) replaced a conventional ground plane, and allowed the antenna to operate with only a 0.5dB reduction in realized gain. This structure was shown by simulations to significantly reduce the normal-incidence monostatic RCS from 4-12 GHz from that of a patch antenna and ordinary ground plane [1].

By optimizing similar ultrasmall, interwoven unit cells to those of the above AMC, different behavior can be obtained for visually very similar structures. These structures were optimized to obtain an equivalent effective permittivity and permeability, where the desired effective material properties were selected to obtain good absorption characteristics at the specified frequencies. The interwoven structure is an example of the flexibility of the design approach – the same geometry, with limited parameters for variation (the lengths and locations of the extensions on the arms), is able to achieve wide variations in electromagnetic behavior [2].

  1. Turpin, Jeremiah P., P. E. Sieber, and Douglas H. Werner. “Absorbing Ground Planes for Reducing Planar Antenna Radar Cross-Section Based on Frequency Selective Surfaces.” IEEE Antennas and Wireless Propagation Letters 12, no. 1 (December 2013): 1456–59. doi:10.1109/LAWP.2013.2288682.
  2. Bayraktar, Zikri, Micah D. Gregory, Xiande Wang, and Douglas H. Werner. “Matched Impedance Thin Planar Composite Magneto-Dielectric Metasurfaces.” IEEE Transactions on Antennas and Propagation 60, no. 4 (April 2012): 1910–20. doi:10.1109/TAP.2012.2186233.