Object Location Estimation Method With Radar Transmitting Vortex Electromagnetic Wave

Compared with conventional radar systems, orbital angular momentum (OAM)-based radar can expand the degrees of freedom for object detection. Previous studies mainly focus on the azimuth measurement but ignore the elevation. The key challenge lies in the simultaneous acquisition of the azimuth-elevation two-dimensional (2D) angle from vortex electromagnetic (EM) waves carrying a limited number of OAM modes. In this paper, the principle of range and azimuth-elevation angle measurement is derived from the mathematical model of radar transmitting vortex EM waves. Furthermore, based on three OAM modes and a single receiver, a closed-form solution of elevation measurement is introduced, and an unambiguous 2D angle measurement method is provided. Compared with the traditional monopulse method, the proposed method ensures 360° full coverage and high precision. Finally, the effectiveness of the proposed method is demonstrated by both simulation and experimental results.