Application of Hilbert-Huang transform to MMW Doppler radar

A millimeter wave (MMW) Doppler radar is introduced. As the Doppler shift is directly proportional to the target speed, the echo is a linear frequency modulated (LFM) signal if the target speed changes linearly. Especially, multicomponent LFM signal exists if the radar is used to analyze the distributed target. The conventional time-frequency analysis methods including short-time Fourier transform (STFT), Wigner-Ville distribution (WVD), and wavelet analysis are not generally adaptive to nonstationary signals. A new approach is proposed to analyze multicomponent LFM signals based on Radon transform and Hilbert-Huang transform (HHT) which is a recently developed method adaptive to nonstationary signals. The echo is decomposed into several Intrinsic Mode Functions (IMF) by the empirical mode decomposition (EMD). After the instantaneous frequency and Hilbert spectrum corresponding to IMFs are computed, target velocity parameter estimation is obtained using Radon transform on the Hilbert spectrum plane. The simulation result shows its feasibility and effectiveness.