Smile face array: Generating oblique incident and front output vortex beam for both TE and TM waves

Abstract

A single layer reflective array is designed to generate orbital angular momentum (OAM) beam at microwave frequency. The unit cell of this design is smile face shape distributed over a planar surface. Phase modulation can be realised by changing the size of each unit cell, with very low variation in reflection amplitude. By careful design, oblique incident can be obtained, reducing feed blockage to the output beam. The direction of the output beam can also be intendedly designed. In this work, the front output is chosen as a demonstrative example. In addition, the input beam can be either TE or TM wave, enable dual-mode operation. Furthermore, it is flexible to design the topological mode of the output OAM. The smile array is developed by cutting slots on circular patch array to produce perturbation on TE and TM waves, so that the difference in TE and TM incidence is reduced. As an instance, the topological modes of l = (−2, −1, 1, 2) are simulated, and the mode l = 1 is fabricated and measured. Measurements are conducted for both near field and far field. The measured results show good agreement with the simulated ones, indicating that this dual mode design works satisfactorily when oblique feed is used.