Doppler effect and micro‐Doppler effect of vortex‐electromagnetic‐wave‐based radar

The vortex electromagnetic (EM) wave carrying orbital angular momentum (OAM) has attracted much attention in radar applications. Aimed at the moving target detection application of vortex EM waves, the Doppler effect and the micro-Doppler (m-D) effect, both including the linear Doppler shift and the angular Doppler shift, are investigated. The theoretical analyses demonstrate that the Doppler effect and the m-D effect in vortex-EM-wave-based radar are significantly more complicated than those in traditional non-vortex-EM-wave-based radar, and can provide additional features for target identification and recognition. Simulations are given to validate the proposed theoretical analyses.