Low-Cost inhomogeneous material for Low-RCS reflectarray antenna implementation

We study a Double-Screen Frequency Selective Surface (DSFSS) mounted on a low-cost inhomogeneous material to design a low Radar Cross Section (RCS) Reflectarray Antenna (RA). Such a DSFSS is a double-sided metallic grating included sub-wavelength cross-shaped patches printed on a porous substrate. Such an artificial substrate is a periodic material made of two alternating dielectrics. The unit cell of such a periodic structure is firstly analyzed by using Method of Moments (MoM). It is shown that DSFSS is a frequency filter with band-stop behavior. Then, such a unit cell is employed to design a single-layer RA. In its design, a phase synthesis approach is applied to optimize the radiation performance of the resultant RA in X-band. Numerical results demonstrate that out-of-band RCS of the designed RA is significantly reduced and the bandwidth of RA is broadened with lower Side Lobe Level (SLL). To validate the obtained results, the designed RA is fabricated and measured. The simulated and experimental results show the proposed low-cost RA has a pencil-beam radiation pattern from 8.7 ~ 12.3 GHz with maximum gain 26.7dBi at 10.5 GHz, and two RCS reduction bands with the fractional bandwidth 200% (in lower band) and 70% (in upper band).