Uniform Circular Array Factor Techniques to Optimize Orbital Angular Momentum Modes Designed with Dipole Antennas at E-band

This paper demonstrates how uniform circular antenna array (UCA) factor and MATLAB® can be combined to study the number of elements required to generate a mode for orbital angular momentum (OAM). The MATBLAB® simulation shows how many elements should be used to generate the radiation pattern without having to design the structures in an electromagnetic simulator first. The capability is demonstrated with an antenna array formed by 8 dipoles designed and fabricated on a 0.127 mm-thick FR4 laminate substrate, with a relative permittivity of 3.65 and loss tangent of 0.013. To improve the overall gain a backside planar reflector is realized by a 0.64 mm thick Rogers RT/duroid 5880. We illustrate that the reflector position will not affect the total OAM mode in the forward direction and only impacts radiation gain. ANSYS HFSS is used to optimize the array, reflector position and feeding network design. The results include simulation and measured far-field radiation patterns, and phase distributions at 73 GHz. The reflector provides 2.2 dB improvement in gain compared to a design without one. The measured radiation pattern is directed in only one hemisphere and agrees with the simulation.