Generation of Vortex Beam using Circularly Polarized Transmitarray

This paper presents the design of a planar transmitarray to generate a spiral phase front in the far-field radiation pattern. The transmitarray is composed of 12 x 12 circularly polarized unit cells, which are rotated individually in order to generate the desired phase distribution. The novel presented unit cell is designed on a double-layer dielectric slab, and three identical metallic sections are positioned on top of each other in a stack. Through rotation of the unit cells a full 360-degree spiral phase progression on the transmitarray can be obtained. The simulated results for the designed spiral phase transmitarray show a desirable performance in the frequency band of 22.5-23.5 GHz ka-band.