OAM modulation induced in millimeter waves using impedance matched flat phase plate

Orbital angular momentum (OAM) based communication has been investigated as it provides an additional degree of freedom to the electromagnetic waves which enables to transmit and receive data in various OAM modes at a given operation frequency, thus increasing the data rate. A method for designing very low reflective flat spiral phase plate that generates OAM modes is proposed in this paper. Such phase plates could provide one or more OAM modes at a signal frequency irrespective of the polarization. The design incorporates variable sizes of perforated unit cells along with matched layers to provide good impedance matching, and the flat disc shape of the phase plate provides the advantage of being compact and easy to install. The OAM phase plate is designed for operation around 30 GHz frequency.