Investigation of Integration for OAM Communication Using Loop Antenna Array and Analysis of Alignment Tolerance for Practical Use

Integration of loop antennas used for Orbital Angular Momentum (OAM) multiplex communication in the 12-GHz band is demonstrated. The antennas are laid out on a Teflon substrate, and the ports are pulled out to the back of the reflector with vias. The measured Isolation of Transmission (IT) for OAM communication at 12.5 GHz is more than 8.6 dB for a communication distance of 15 mm. In addition, the effects of misalignment on communication performance are estimated by simulation and measurement with the arrays. By electromagnetic field simulation, the higher the mode order is, the larger the decrease of IT for misalignment. For the highest 4th-order mode, the IT is shown to be reduced to less than 0 dB for the misalignment of the translation by more than 2 and 4 mm along the X- and the Y-axis, respectively. On the other hand, the effects are reduced to 0 dB for rotations of 30°, 20° and 20° around the X-, Y- and Z-axis, respectively. The measured performance for the misalignment is similar to that in the simulation results, but the IT does not decrease in descending order of the mode order.