Detection of Rotational Object in Arbitrary Position Using Vortex Electromagnetic Waves

Detection of the rotational objects in arbitrary position, using vortex electromagnetic (EM) waves carrying orbital angular momentum (OAM), is studied in this paper. In addition to the traditional linear Doppler shift, the rotational Doppler shift in OAM-based radar system can provide more detailed features of the object. Firstly, the Doppler detection model in OAM-based radar system is established, the linear Doppler and rotational Doppler frequency shifts are derived and verified. Subsequently, the detection method of rotational object using vortex EM waves, including an effective linear and rotational Doppler separation and a motion parameter estimation method, is proposed. Theoretical and simulation results validate the effectiveness of the proposed method, and more detailed rotational parameters can be obtained by using vortex EM waves in OAM-based radar system, compared to the method using plane waves in conventional radar system.