Alteration of Electromagnetic Scattering Using Hard and Soft Anisotropic Impedance Surfaces

The scattering from a rectangular metal sheet is altered by patterning the surface with hard and soft anisotropic impedance surfaces. A plane wave incident normally to an edge of a metal rectangle will have maximum backward scattering in the direction of the source for both transverse magnetic (TM) and transverse electric (TE) polarizations. This scattering lobe is manipulated by patterning the metal sheet in two sections. A hard surface is applied to the incident region which reflects neither TM nor TE waves from the front edge. Similarly, a soft surface prevents reflections of both polarizations from the back edge. The surfaces are patterned with an angled boundary, so that surface waves and incident radiation are scattered at an angle instead of backward. Unit cells are designed and analyzed for both regions for operation centered at 15 GHz. A surface is fabricated and measured, and the scattering alteration effect is achieved over a large bandwidth for each polarization. Curved and zigzag geometries are also discussed.