Realization of Multimode OAM Beams with Almost the Same Divergence Angles

Abstract

This paper proposes a new method of realizing multimode OAM beams with almost the same divergence angles. The theoretical relationship between the divergence angle of the OAM beam and its radiation source is presented, and the radiation source distributions for various mode OAM beams with the same divergence angle range are discussed. In order to verify this method, an eight-mode OAM antenna constructed by a bifocal parabolic reflector and dual OAM feeds is designed and simulated. The simulation results show that the divergence angle ranges of 3 dB beamwidth for OAM modes l = ± 1 , ± 2 , ± 3 , ± 4 are 2 . 2 ° , 4 . 6 ° , 2.2 ° , 5.0 ° , 2.4 ° , 4.4 ° , and 2.6 ° , 4.8 ° , the divergence angles corresponding to the maximum beam directions are 3.5 ° , 3.6 ° , 3.5 ° , and 3.8 ° , respectively, and the maximum difference is within 0.3 ° .

Metasurface modulator of frequency diverse multi-mode OAM beams with equal divergence angle for coincidence imaging

“…As shown in figures 17 and 18, ±1-mode, ±2-mode, and ±3-mode OAM beams can be generated by the FDMM OAM The performance comparison between the FDMM OAM modulator and existing works is shown in table 2. Compared with the MM-OAM-generation methods in [17,18], and [31], there is no complex feed network in the proposed method. Compared with designs in [30] and [32], this work can simultaneously generate different modes of OAM beams with approximately equal divergence angles.…”

“…Well-known methods of generating OAM beams including the helical phase plate [14,15], the rotating paraboloid [16,17], the uniform circular array (UCA) [18,19], and the metasurface modulator [20,21] have already been proposed. The metasurface aperture is an effective electromagnetic control method since the metasurface can be designed with multiple degrees of freedom, such as geometry of the metasurface units, dispersion, and polarization response, etc.…”