Time-Frequency Characteristics of the Near-Field Micro-Doppler Effect in Passive Radar

In this paper, the time-frequency characteristics (TFC) of near-field micro-Doppler (MD) effect induced by blade rotation in passive radar are analyzed. Firstly, the electromagnetic scattering mechanisms corresponding to different blade flashes in the spectrogram are summarized. It shows that the TFC of the blade echo are composed of the TFC of the tip scattering points echo and the mirror reflection points echo. On this basis, the signal model of the near-field blade echo is established, and the TFC of the above mentioned scattering centers are derived, which together constitute the TFC of the whole blade echo. The results indicate that the blade flashes in the spectrogram of near-field MD effect present more complex shapes and characteristics than those under far-field condition. The simulation and experimental results validate the analysis conclusions.