20-GHz Focusing Antennas Based on Corrugated Waveguide Scattering

We propose a focusing antenna based on corrugated waveguide scattering at 20 GHz. Surface waves propagating on a low-loss 1-D corrugated waveguide are scattered out of the waveguide to form a focus in the free space. The scattering is caused by a chirped grating structure incorporated on the waveguide, which is designed to involve constructive interferences at a predefined focal point. In this letter, we describe the fabrication and excitation of the antenna and experimentally demonstrate focusing at 30 cm above the structure at 20 GHz. The antenna allows for beamforming of millimeter waves with a simple planar structure.