Experimental results of triply multiplexed microwave orbital angular momentum mode transmission

Power and isolation characteristics of triply multiplexed microwave orbital angular momentum (OAM) modes from 3×4 Butler matrix and uniform circular array antenna (UCA) are measured using 25cm diameter Cassegrain reflector. For doubling the transmission distance 0 mode power decreased ∼5dB but ±1 mode power decreased ∼10dB and the difference exceed 20dB when the transmission distance is over than 10M. Also the intermodal isolation was more than 12dB at 10M apart and expected above 8dB up to 20M distance if the 0 mode power was controlled for reducing the crosstalk to the ±1 channel.