Broadband RCS reduction and gain enhancement microstrip antenna using shared aperture artificial composite material based on quasi-fractal tree

A shared aperture artificial composite material (SA-ACM) with broadband absorption and partial reflection feature is proposed. The SA-ACM is composed of artificial composite material absorber (ACMA) and partial reflection surface (PRS), where the ACMA and PRS share the same aperture in the vertical dimensionality. The ACMA consists of quasi-three-dimensional fractal tree loaded with lumped resistances and metallic pattern on the bottom side of a dielectric slab, and the PRS consists of etched parallel slots in a metallic plane. The SA-ACM as the role of superstrate is applied to the mircrostrip antenna. The Fabry–Perot resonator cavity constructed by the PRS and the metallic ground of the mircrostrip antenna can achieve high gain, while the ACMA can obtain the low radar cross section (RCS) characteristic by absorbing the incident wave. Simulation and experiment results demonstrate that the gain of the antenna with SA-ACM is enhanced over 3 dB in the operation frequency band, and the backscattering RCS is obviously reduced by 10 dB in a wide frequency range.