Abstract
In order to extend the applications of vortex waves, we propose a water-immersed rectangular horn antenna array for generating underwater vortex waves carrying the orbital angular momentum (OAM). Firstly, a single dielectric-loaded rectangular horn antenna with the central frequency of 2.6 GHz was designed for generating underwater electromagnetic (EM) waves. Due to the supplementing dielectric-loaded waveguide in this single antenna, the problems with difficult sealing and fixation of the feed probe could be solved effectively. The simulation results show that it has a good impedance characteristics (S11 < −10 dB) and reasonable losses (less than 3.5 dB total for two antennas and a coaxial line) from 2.5 GHz to 2.7 GHz. Experiments on the single antenna were also carried out, which agree well with the simulations. Based on the designed single antenna, the water-immersed rectangular horn antenna array was proposed, and the phase gradient from 0~2π was fed to the horn antennas for generating underwater OAM waves. The simulation results demonstrate high fidelity of the generated OAM waves from the intensity and phase distributions. The purity of the generated OAM modes was also investigated and further verifies the high fidelity of the generated OAM waves. The generated high-quality OAM waves meet the requirements for underwater applications of OAM, such as underwater communication and underwater imaging.
Highlights
As is well known, vortex waves carrying orbital angular momentum (OAM) have a rotating phase factor of eilθ, where θ is the azimuth angle, and l is an integer number called “topological charge”, which corresponds to the order of the OAM modes
In this paper we describe the design and testing of a single water-immersed rectangular horn antenna, which can generate underwater EM waves
As the approach based on the phased uniform array is very flexible and controlled, it is
Summary
Vortex waves carrying orbital angular momentum (OAM) have a rotating phase factor of eilθ , where θ is the azimuth angle, and l is an integer number called “topological charge”, which corresponds to the order of the OAM modes. There are numerous generation methods of OAM-carrying waves in the radio domain [14]: antenna array [8,15,16], microstrip patch antenna [17,18], spiral phase plate (SPP) [19], spiral antennas [20,21,22], slot antennas [23], cylinder dielectric resonator antennas [24], horn lens antennas [25], and so on. In this paper we describe the design and testing of a single water-immersed rectangular horn antenna, which can generate underwater EM waves. Based on the above single antenna, we designed and simulated a water-immersed OAM rectangular horn antenna array.
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