Improved Performance for 8-channel multiplexing OAM communication by suppressing Interference

Improved signal to interference ratio (SIR) is demonstrated for 8-channel multiplexing OAM communication with loop antenna arrays in a 5 GHz band. Current distributions are scrutinized, and the unique scattering of the OAM waves by the feeding coaxial cables is shown to undermine the orthogonality for the OAM waves. Induced interference waves are shown to be reduced by implementing resistors at the antinodes of the current on the antennas of the orthogonal port azimuth. The signal wave is not affected, because the position of the resistor becomes the node for the signal wave. With the configuration, 8-element arrays are designed and fabricated, and the measured SIR for the communication distance of 3 cm is better than 9.7 dB at 5.21 GHz. The measured SIR is improved by 6.2 dB by implementing the resistors.