Polarization-Independent Backscattering Enhancement of Cylinders Based on Conformal Gradient Metasurfaces

The electromagnetic backscattering enhancement of both elliptic and circular conducting cylinders is investigated in this paper through the design of conformal and polarization-independent gradient metasurfaces. The presented metasurface designs employ varying phase gradient along the circumferential direction of the involved cylinder so that effective retroreflection can be achieved through redirecting the scattering dispersed by the conducting cylinder back to the direction from which the plane electromagnetic wave is coming. Supported by a grounded thin substrate with a relatively high dielectric constant, a modified loop array with compact unit cell is used to implement the nonuniformly or uniformly sampled phase gradient of the metasurface. It is observed that the metasurface-coated elliptic and circular cylinders can generate backscattering very close to that by corresponding flat conducting plates with their main planes perpendicular to the incident wave vector, for both transverse magnetic (TM) and transverse electric (TE) polarizations. Compared with the conducting cylinders without coating, the backscattering is thus effectively enhanced by the conformal gradient metasurfaces. Good agreement between simulated and measured backscattering results validates the observations.