A Broadband RCS Reduction Coating Using a Novel Arrangement of Metasurface Unit Cells Based on Two Substrates

In this paper, a new coating structure is proposed for broadband radar cross section (RCS) reduction using 1-bit metasurfaces. The designed structure consists of two types of unit cell, arranged in concentric square rings. The substrate of unit cells is different, FR4 and Ultralum-2000 with thicknesses of 2.4 and 0.762 mm, respectively. The proposed structure shows an ultrawideband property to reduce the RCS, less than -10 dB, in the frequency range of 14-45 GHz. This range covers part of Ku-band (14-18 GHz), K-band (18-27 GHz), and Ka-band (27-40 GHz) and part of millimeter-wave band (40-45 GHz). To validate the designed work and simulation results, a prototype with the dimension of 84 x 84 mm2 is fabricated and tested. Also, the RCS reduction is determined analytically and presented. The measured results verify well the analytical and simulation results. In short, this work includes three new points: (1) the use of two substrates with different thickness and dielectric constant to design unit cells, (2) a new arrangement of array cells in the form of concentric square rings, and (3) achieving a great bandwidth to reduce RCS.