Generating and Steering Quasi-Nondiffractive Beam by Near-Field Planar Risley Prisms

A phase shift surface (PSS) antenna launching steerable quasi-nondiffractive beam is proposed in this article. The principle of the far-field beam-steering antenna using the Risley prism is introduced to the near-field nondiffractive beam antenna. To match the specific phase distribution requirement of the scanning quasi-nondiffractive beam, the linear phase shift distribution on the Risley prism is reconstructed as a nonlinear one. The quasi-nondiffractive beam with considerable and stable depth of field can be steered within the front hemisphere of the antenna by mechanically rotating two PSSs. A prototype antenna is fabricated and its near-field patterns are measured. The scanning range of the beam is from 0° to 54° in zenith and from 0° to 360° in azimuth. The beam's direction and its depth of field remain stable within the frequency band of 27-29 GHz. The beam maintains accurate direction and stable depth of field during the steering process.