Multi-scale bullseye antennas.

We design, simulate and experimentally characterize a multi-scale bullseye antenna for the broadband manipulation of microwaves. The device achieves far-field beam-forming via tailored diffraction at the interface between two concentric bullseye geometries, with near-field energy concentration resulting from the overlap of the diffracted beams. This article is part of the theme issue 'Wave generation and transmission in multi-scale complex media and structured metamaterials (part 1)'.