Radiation Pattern Synthesis for the Generation of Vortex Electromagnetic Wave

Radiation pattern synthesis methods for the generation of orbital angular momentum (OAM) beams based on circular arrays are proposed. The concentric-ring arrays are designed to suppress the side lobes of the radiation pattern firstly. Based on the genetic algorithm, two objective functions are defined to calculate the signal amplitude of each ring. Simulation results show that the proposed method can effectively suppress the side lobes, lower than -30 dB. Subsequently, for electromagnetic vortex imaging, the beam steering technique is applied to enhance the directivity of vortex beams for different OAM modes. Analyses indicate that large steering angle would lead to some distortion of the phase-front distribution. Finally, the imaging model after beam optimisation is established and the sparse Bayesian method is exploited to image the target with high resolution. The work can benefit the generation of OAM-carrying beams and its wide applications in radio communication and radar imaging.