Theoretical and Experimental Analysis of Radar Micro-Doppler Signature Modulated by Rotating Blades of Drones

Abstract

Radar signatures contributed by rotating blades of drones usually refer to the kinematical micro-Doppler phenomenon on spectrograms. Here, theoretical analysis indicates that when sampling time is short enough that this signature becomes instant micro-Doppler signatures with scattering characteristics, appearing as “blade flash” in the time domain and rotor blade modulation (RBM) feature in the spectrum. In an anechoic chamber, we track this instant micro-Doppler signature by using a dynamic measurement system composed of a network analyzer and a high-speed camera to collect high-resolution range profile of a consumer drone, DJI Phantom 3 Vision within S-band, X-band, and Ku-band. The experimental results demonstrate that rotating blades do cause signal fluctuation of “blade flash” and register the RBM feature in the spectrum, and the modulation effects are weak within S-band, strong within X-band, and stronger within Ku-band. This instant micro-Doppler with scattering characteristic establishes a mapping between radar signature and the rotation structure component of the drone and enables us to distinguish a drone from other nonblades objects in the air, especially with little radar observation time.