Patent

This patent protects a steerable beam antenna for microwave frequencies based on the mechanical Risley rotation principle, but with a new design strategy to significantly improve the Side Lobe level performance. It comprises:
1) a feeding structure having at least one part mounted for rotation about a longitudinal axis of the antenna, capable of implementing a prescribed phase shift law. An embodiment of this part can be a metasurface, illuminated by a stationary horn antenna, as done in the developed prototype.
2) a stacked metasurface composed of sub-wavelength unit-cells capable of rotation about said longitudinal axis, with its aperture orthogonal to said longitudinal axis.

The novelty is that an additional phase function is added to structure 1), and the same function is subtracted from structure 2) so that the combined behavior cancels out, to recover the Risley Prism
requirement. However, the added phase function introduces a periodicity break in structure 1) and 2) individually, which is otherwise responsible for the appearance of high side lobe level.