Application of transformation optics in radar cross section reduction of targets with arbitrary two-dimensional geometries

Abstract

Transformation optics (TO) provides an unconventional approach to control electromagnetic (EM) waves in an arbitrary manner. In this study, a new strategy of radar cross section reduction (RCSR) was proposed for two-dimensional (2D) targets of arbitrary shape. Applying a complex coordinate transformation allowed us to control both the amplitude and the phase of EM fields. Inspired by the black hole concept, a swampy coating layer (SCL) was designed to make EM fields spin around the target and dissipate gradually. To achieve this goal, a complex Archimedean coordinate transformation function was exploited. This forced the incoming EM waves to propagate on a lossy path that was longer than the conventional radar absorbing materials (RAMs). Hence, it provided sufficient time for the SCL to dissipate the trapped EM wave. Depending on the target size, the SCL materials were analytically derived based on the coordinate transformation theory. However, these materials are feasibly independent of the target geometry and its constitutive materials. Several examples were provided to highlight the capability of the proposed TO-based strategy. This method reduced the radar cross section of 2D targets with irregular geometries and different materials. Numerical simulations were carried out to verify the feasibility of design by using a composite of the split ring resonator-meander line array. A significant RCSR level was noticed whose operating bandwidth was dictated by the employed metamaterial unit cell. So, the simplicity of the design sacrificed the RCSR bandwidth. Therefore, this paper revealed a new class of TO-based RAMs for 2D arbitrary-geometry targets of different materials.