MODIFIED HILBERT-HUANG TRANSFORM AND ITS APPLICATION TO MEASURED MICRO DOPPLER SIGNATURES FROM REALISTIC JET ENGINE MODELS

Joint time-frequency analysis (JTFA) is applied to micro Doppler signatures generated by jet engine modulation (JEM) effect using a modified Hilbert-Huang transform (HHT). The modified HHT is developed to improve the JTFA results of measured JEM signals. Wavelet decomposition (WD) with Meyer wavelet function is considered as a supplementary process of the HHT. The modified HHT examines a signature obtained from simulation of a jet engine CAD model, and is then applied to the signatures obtained from measurement of two realistic jet engine models. The modified HHT gives more improved JTFA results of the measured JEM signals than those from the simple short-time Fourier transform - (STFT) based analysis. The modified HHT-based JTFA approach is expected to be significantly useful for enabling high-quality radar target recognition in a real environment by complementing other traditional analyses.