| Wireless communication has been developing rapidly with the main development trend of high rate and high bandwidth. However, the scarcity of spectrum restricts the development. Orbital angular momentum (OAM) is a new degree of freedom and its various modes are orthogonal to each other. Theoretically, the number of OAM modes is infinite. These features are the basis of improving communication rate and coding efficiency. Electromagnetic beam carrying OAM not only has the properties such as frequency, phase and polarization, but also has the new dimension of OAM. Therefore, it can be used for multilevel modulation to improve spectrum efficiency and communication capacity at the same time. So, it becomes a research hotspot in the field of electromagnetic field and communication.This paper is mainly concerning on the traveling-wave circular loop antenna (CLA) and a ring resonator antenna based on this CLA. Under the condition of ideal feed, it is verified the CLA can generate electromagnetic beam carrying OAM by establishing model, theoretical calculation and electromagnetic simulation. However, the antenna loss is inevitable and constant current intensity on CLA cannot be realized. Then the paper studied the influence of the loss on the OAM radiation characteristics of CLA. A certain loss will cause the imperfect of the phase and the uneven of the amplitude. Thus, adopting multipoint feeding technology is put forward to improve antenna performance. Finally, by a series of calculation, simulation and experiment, the OAM radiation characteristics of the ring resonator antenna based on CLA is studied. It is verified the correctness of the OAM generator using CLA and the rationality of the solution to loss.This paper studies the OAM radiation characteristics of the CLA. At the same time, considering the influencing factors, it has put forward further improvement schemes and done the related experimental verification. |
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