Design of a Wideband Vortex Beam Reflectarray Using Subwavelength Element

A new subwavelength reflective unit cell is designed and used in reflectarray to generate orbital angular momentum (OAM) waves. The metallic single layer subwavelength element consists of a cross dipole patch, four symmetric square patches and a loop patch, which is printed on one side of a substrate layer. An air layer is also inserted between metallic ground and the substrate. Size of the square unit cell is quarter wavelength at designed frequency and it achieves 360 degrees reflection phase range. A reflectrarray is designed to generate OAM waves of mode 1 for linearly polarized feed at 6 GHz. Using the proposed subwavelength element, its far-field radiation patterns and E-field phase distribution are analyzed through CST Microwave Studio. The simulated results show that the required OAM waves are generated successfully with a maximum gain of 23.3 dBi at 6 GHz.