Generation of Multimode Orbital Angular Momentum Waves Using Wearable Array Antenna

In this paper, a flexible wearable antenna based on uniform circular array of four identical microstrip patch antennas on a felt textile substrate was designed to generate multiple orbital angular momentum (OAM) modes. The proposed antenna was simulated and analyzed to confirm the generation of OAM mode +1 and −1. The concept of reconfigurable method with 16 p-i-n diodes was implemented for the switching purpose. The proposed antenna covered overall bandwidth above 700 MHz for both the modes in free space while the obtained gain by mode 1 was 1.981 dBi and mode −1 was 1.993 dBi. Moreover, the mode purity analysis was carried out to verify the generation of OAM mode +1 and −1 with acceptable SAR value. The purity obtained was 47.78% for mode +1 and 47.91% for mode −1 at free space. This study shows that using textile antennas for modal multiplexing to produce multimode OAM waves is feasible in order to increase channel capacity and spectrum efficiency.