This paper presents the generation of modes of angular momentum of the orbital type using a proposed array antenna fed with Rotman lens of multiple layers of compact size. The gain of orbital angular momentum is enhanced by the proposed microstrip antenna, which is a circular array antenna with nine elements fed with Rotman lens utilizing the patch element of high gain. Antenna gain can be enhanced in an effective manner; the patch element is attached with two slots loaded in a stacked patch. The circular array when employing the feeding network with Rotman lens causes excitation of different input ports, which produces carrying beams of orbital angular momentum with mode numbers m = 0, m = ±1, m = ±2, m = ±3, and m = ±4. A phase shift of 160 deg is achieved on the output ports in the adjacent position for meeting the requirement of the phase of orbital angular momentum modes of m = ±4. The detection angle of the ports of the beam and array is adjusted by modifying the Rotman lens for achieving the uniform distribution of amplitude on the output ports of the antenna. Therefore, effective improvement is observed in the radiation pattern of the orbital angular momentum beams, which obtains equal amplitude in all the output ports. The fabrication of a prototype antenna of C band is done, and measurements are performed. Simulated results match the measured results, indicating that generation of orbital angular momentum is done by the antenna proposed in this paper, which can be used in communication systems based on orbital angular momentum.
