Research on rotational speed measurement technology for rough-surfaced targets based on rotational Doppler effect

This study investigates the application of superposed vortex beams in rotational speed measurement for rough-surfaced targets. In conventional radar systems, the linear Doppler effects is primarily used to detect target radial velocities, but fundamentally fails to resolve angular motion parameters. The rotational Doppler effect in vortex beams carrying orbital angular momentum (OAM) addresses the limitations of angular motion detection in conventional radar systems. However, random surface roughness of the target distorts the extraction and analysis of rotational Doppler shift signals. Through experimental generation of superposed vortex beams with identical topological charges but opposite signs, this work systematically explores the impact of rotating randomly rough surfaces on rotational Doppler shifts. Experimental results reveal that the Doppler shift signals correlate with the spacing of OAM mode spectral components. Leveraging the OAM spectral distribution characteristics, a rotation speed demodulation method based on shift interval is proposed, offering a novel approach for measuring rotational speeds of complex rough surfaces.