Millimeter-Wave OAM Dipole Array with Reflector

This paper introduces a planar 8-element dipole array with a reflector for generating orbital angular momentum (OAM) mode 1 at 73 GHz in only one direction. The 8-element dipole array is 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. The backside reflector is realized by a 0.64 mm thick Rogers RT/duroid 5880 board with a relative permittivity of 2.2 and loss tangent of 0.0009. Finite element method simulations optimized the array, reflector and feeding network designs. The results include simulated and measured far-field radiation patterns, phase distributions and vertical bar S-11 vertical bar (dB). 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.