Wideband, Wide Angle, Polarization Independent RCS Reduction Using Nonabsorptive Miniaturized-Element Frequency Selective Surfaces

A thin, wideband, nonabsorptive radar cross section (RCS) reducer (NARR) layer capable of operation over a wide range of incident angles and for any arbitrary incident wave polarization is presented. The design is based on implementation of two different types of subwavelength miniaturized-element frequency selective surfaces (MEFSS) backed by a thin grounded dielectric substrate. Two MEFSS structures are designed in such a way to produce reflection phase values with a difference of about 180 degrees (+/- 30 degrees) over a wide frequency range. Segments of these surfaces are arranged in periodic and aperiodic fashions to distribute the scattered energy and minimize the maximum bistatic RCS of the underlying metallic surface over a wide range of incident angles at both polarizations. It is shown that the aperiodic NARR structure has 3-dB lower maximum bistatic RCS compared to the periodic one. The -6 dB bistatic RCS reduction bandwidth of 66% is achieved for both periodic and aperiodic NARR surfaces at the normal incidence. The monostatic RCS reduction level at normal incidence is the same for both structures, but the aperiodic NARR layer is shown to provide 13% higher -10 dB bandwidth. In addition, the performance of both structures for oblique angle of incidence up to 50 degrees is examined and is shown that the aperiodic NARR layer shows better performance in suppressing the RCS sidelobes. As a partial experimental validation, two prototypes of periodic and aperiodic NARR layers are fabricated and their monostatic RCS reduction are characterized experimentally. The measured results are in good agreement with the corresponding simulations.