Evaluation of Different Phased Array Approaches for Orbital Angular Momentum Beam Steering

This paper presents several approaches for beam steering of vortex waves that are generated by a Uniform Circular Patch Array (UCA) operating at 10 GHz. Firstly, we design and evaluate a uniform circular patch array with 8 patch antennas. For the beam steering of Orbital Angular Momentum (OAM) waves two different types of phasing are necessary, firstly the azimuthal OAM phasing of the UCA elements, and secondly the global circular array phasing for beam steering. The steering works well up to the steering angle of 20°, where the gain difference between the two lobes is less than 3 dB. Secondly, we use the same UCA but with 4 elements instead of 8 elements. Each antenna element will be replaced with 3 different subarrays of 4 antennas (linear, rectangular and circular). These 4 approaches are compared to each other. Here, there is an additional phase shift, which will be called local subarray phasing. The rectangular array shows a better performance compared to the other forms. The advantage of using an array is, that the steering is working good up to an angle of 30°.