Low Sidelobe Orbital Angular Momentum Vortex Beams Based on Modified Bayliss Synthesis Method for Circular Array

Abstract

Electromagnetic orbital angular momentum (OAM) vortex beam patterns generated by conventional methods are always of high sidelobe level, which severely limits its application. Considering the sidelobe suppression abilities of Bayliss synthesis method for difference beams, we present a modified Bayliss synthesis procedure to obtain low sidelobe OAM vortex beams. The Bayliss synthesis method cannot suppress the sidelobe level of difference pattern to the desired value when the element number of linear array is relatively small. By modifying the original zero locations that need to be removed in Bayliss pattern, we can further suppress the sidelobe level of difference pattern. This can be called the modified Bayliss pattern. Finally, by expanding the proposed synthesis method from linear source to circular array, theoretical results show that sidelobe levels of OAM beams can be suppressed to less than −30 dB when OAM mode number varies from <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l</i> = 1 to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l</i> = 10. The proposed low sidelobe OAM vortex beam can be applied in antijamming communications of near-field in the future.