Alignment Aspects of OAM Signal Reception Using Rotman Lens Based Circular Array

Abstract

This paper discusses orbital angular momentum (OAM) signal reception and alignment aspects using a Rotman lens based multimode circular patch antenna array. A 9-element planar circular array is connected to a 5 beam port Rotman lens which is capable of hosting 5 spatially orthogonal OAM modes namely $l = 0, \pm 1$ and ±2. The Rotman lens based circular array is paced at the receiver end when it is illuminated with OAM signals. It is shown that the OAM modes reception is separable at the Rotman lens stage, hence reducing the requirement of the OAM phase correction at the receiver’s signal processing block. It is also shown that a slight misalignment between transmitter and receiver circular arrays can substantially decrease the signal recovery chances for the transmitted data using the OAM modes $l = \pm1$ and ±2. This feature can enhance physical layer security to the communication link using Rotman lens based multimode circular array.