Electromagnetic Vortex Enhanced Imaging Using Fractional OAM Beams

Electromagnetic (EM) vortex can realize high resolution imaging in forward-looking observation geometry without relative motion between the radar system and targets. However, the current research about EM vortex imaging only exploits integral orbital angular momentum (OAM) beams, which limit the application in the real scene with the existence of noise. An EM vortex enhanced imaging method based on fractional OAM beams is proposed against noise effect in this letter. Firstl the generation method of fractional OAM beams with phase distribution of nonintegral OAM mode is proposed using uniform circular array, and the corresponding features are analyzed. Subsequently, the imaging model and scheme with fractional OAM beams are provided and the principle for enhancing imaging performance is derived. Finally, results by Monte Carlo simulations demonstrate that the proposed vortex imaging method based on fractional OAM beams is robust against noise effect and can achieve better imaging performance in low signal-to-noise ratio (SNR) environment, which is of prospect for overcoming the shortage of poor imaging performance in low OAM order and complex noise scenario. This letter benefits the development of EM vortex imaging.