Spatiotemporal Evolution of Orbital Angular Momentum (OAM) Beams Based on a Uniform Circular Frequency Diverse Array (UC-FDA)

Radar imaging based on orbital angular momentum (OAM) beams has become a significant approach to realize high resolution and multidimensional target detection. The irradiation of a target area with OAM beams with different modes has been proven to be a feasible solution to improve the azimuthal resolution of the target. This article is the first to propose and validate novel spatiotemporal OAM beams generated by a uniform circular frequency diverse array (UC-FDA). Unlike the conventional uniform circular array (UCA), signals with frequency intervals need to be fed to the antennas in the UC-FDA structure. The mode of the spatiotemporal OAM beam can be switched automatically with spatial transmission, which enhances the flexibility of mode switching and reduces the switching time. The evolution characteristics of the OAM beam are fully demonstrated. Meanwhile, the intrinsic spatiotemporal evolution rules and influence parameters are analyzed and summarized. Furthermore, an optimized dynamic mode decomposition (DMD) algorithm is proposed and used to implement mode detection. Finally, the spatiotemporal evolution of OAM beams is applied to a rudimentary exploration of radar imaging. The measured results indicate that azimuth imaging of targets can be successfully accomplished. Spatiotemporal OAM beams may unlock promising potential for new-tech radar scenarios.