Synthetic Multimode Orbital Angular Momentum Generation and Its Object Detection Application

This study proposes a novel method for generating virtual orbital angular momentum (OAM) using a synthetic uniform circular array (SUCA). In the proposed method, the base array is rotated to various spatial locations, with the feeding phases modified accordingly, and the generated fields at various spatial locations are superimposed. The proposed method exchanges the cost of the time domain for more spatial degrees of freedom, which can overcome the limit of space and configure more virtual array elements to generate vortex electromagnetic (EM) waves carrying virtual multimode OAMs. To validate the effectiveness of the proposed method, a radially placed SUCA is designed with four actual elements of a circularly polarized (CP) horn antenna and sixteen virtual elements. The SUCA is then simulated and measured, and it successfully generates fifteen virtual OAMs in the frequency range of 5-6.5 GHz. Furthermore, 2-D object detection experiments of three metal targets with different scales at different positions based on the SUCA were conducted. The experimental results show that the three targets can be distinguished clearly, indicating that our work has the potential to generate more virtual OAMs and improve object detection resolution in practical applications.