Passive and Lossless, Closed Metasurfaces for Illusion Electromagnetics

A two stage algorithm for the design and optimization of three-dimensionally contoured metasurfaces is presented. The first stage involves integral equation modeling and a moment method solution resulting in a local active/lossy design. The second stage involves optimization. It uses the gradient descent method and a semi-analytic gradient calculation using the adjoint variable method to obtain a non-local passive/lossless metasurface design with identical far field performance to the local active/lossy design. An example of an electromagnetic illusion is presented for a cubical metasurface which scatters the fields of a PEC sphere.