Generation and Processing of Electromagnetic Vortex Beams with Different Orbital Angular Momentum Mode Orders

The permanently and ever-growing request for accurate, efficient, compact, cost-effective, high performance, and novel applications have inspired the researchers to detect new advanced techniques. After the successful deployment of the electromagnetic waves in the last decades in the field of wireless communication (GSM, LTE), sensing, navigation and positioning (GPS), detection and localization (RADAR), identification (RFID), imaging and mapping (SAR), and biomedical engineering (MRI), the vortex waves submit new methods to improve these fields
more than the plane waves. Therefore, the vortex waves, also known as Orbital Angular Momentum (OAM) waves, are the main subject in this thesis set under investigation to explore some new approaches that can be applied to wireless technology.

Therefore, in this work, the conventional approach of uniform circular antenna array (UCA) and the elliptical patch approach are set to be compared together to a new approach based on crossed 2 lambda-dipole antennas (CDA) in order to generate vortex waves. The recent approach is a simple suggestion for generating vortex waves with radial polarization which is performed through using two or four crossed 2 lambda-dipole antennas. Upon the usage of a reflector, the radiation of this approach can be increased and focused.

Furthermore, an OAM beam steering has been implemented by the aid of uniform circular antenna array in which two different types of phase shifts are required for the beam steering unlike the UCA with subarrays (linear, circular, and rectangular), where three different ones are needed. The two approaches are simulated and studied to achieve better results thus solving the serious issue for OAM wireless communication knowing that the misalignment between the OAM transmitter and the OAM receiver is a very crucial point.
Moreover, the large beam divergence inherent to vortex waves has been reduced by the aid of a new special lens and reflector. Both the tailored lens and reflector are constructed by an appropriately designed form function rotated around the center axis of the uniform circular antenna array (UCA) to be compared to the conventional one, then showing better simulated and measured results. Further, similar to the misalignment issue, the beam divergence reduction is
also crucial for many applications such as wireless communication where the long-distance is seen as an obstacle, or such as the target detection and localization where the beam divergence reduction allows the resolution enhancement of the localization.
Finally, with the aid of helically arranged dielectric resonator arrays, a new application of vortex waves has been developed by converting an incoming OAM mode order min to an outgoing OAM mode order mout. This application offers likewise improving the code number in the domain of Radio Frequency Identification (RFID) through new multi-valued digits rather than the conventional binary coding {0;1}. Also, these helically arranged dielectric resonator
arrays are characterized by the rejection of the clutter from broadside direction due to the Butler matrix (BM), where the phase shift of the clutter interferes destructively unlike the DR-coded OAM-signal which interferes constructively.


Citation style:
Could not load citation form.


Use and reproduction:
All rights reserved