CIRCULAR POLARIZED PATCH ANTENNA GENERATING ORBITAL ANGULAR MOMENTUM

The recent extension of the orbital angular momentum (OAM) concept from optical to\udmicrowave frequencies has led some researchers to explore how well established antenna techniques can\udbe used to radiate a non-zero OAM electromagnetic field. In this frame, the aim of the present paper is\udto propose a new approach to generate a non-zero OAM field through a single patch antenna. Using the\udcavity model, we first analyze the radiated field by a standard circular patch and show that a circular\udpolarized (CP) TMnm mode excited by using two coaxial cables generates an electromagnetic field with\udan OAM of order ±(n−1). Then, in order to obtain a simpler structure with a single feed, we design an\udelliptical patch antenna working on the right-handed (RH) CP TM21 mode. Using full-wave simulations\udand experiments on a fabricated prototype, we show that the proposed antenna effectively radiates an\udelectromagnetic field with a first order OAM. Such results prove that properly designed patch antennas\udcan be used as compact and low-cost generators of electromagnetic fields carrying OAM