Rotational Doppler Effect Based on Reconfigurable Circularly Polarized OAM Array

Orbital angular momentum (OAM) radar is a new type of radar that can provide azimuth information about targets in the field of detection and imaging. However, previous OAM radar systems have not explored the contribution of spin angular momentum (SAM) and the capability for dynamic switching of the transmitted OAM mode, thereby limiting their resolution for imaging applications. This study introduces a meticulously designed circular patch antenna with an array equipped with adjustable input phases to generate reconfigurable circularly polarized OAM (CPOAM) beams. Furthermore, by establishing an S-band radar system, we investigate the rotational Doppler effect (RDE) of different orders of CPOAM for the first time. This study directly estimates the rotational speed and direction of rotating objects. Three different combinations of SAM and OAM were utilized to test the rotation information of the target; the influence of the micro-Doppler effect can be significantly suppressed, achieving a minimum detection speed of 21 rad/s and a maximum detection error of 2.4%, indicating a high level of estimation accuracy. This approach holds significant potential for target detection, tracking, and monitoring applications, enhancing the performance and reliability of related technologies.