Modified Hilbert-Huang Transform and Its Application to Measured Micro Doppler Signatures From Realistic Jet Engine Models

Abstract

Abstract-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.

Extended High Resolution Range Profile-Jet Engine Modulation Analysis With Signal Eccentricity

“…The chopping rate [6,11], the period when a blade moves to its neighbor position, can be calculated as 0.435 ms. The blade length is estimated using the Doppler span [8,10,11] along the frequency axis. The slanted waveforms marked with white lines suggest the odd number of blades for which the blades alternately approach and recede [8].…”

“…In our previous work [12], an algorithm for automatically determining the jet engine location was proposed and basically postulated that after eliminating frequency components around the zero-frequency, the range cell related to the jet engine location had higher amplitude than other cells by the remaining 1st chopping harmonic of the JEM spectrum [10,11]. However, this non-parametric approach does not consider the inherent signal characteristics, and ambiguity can arise from the threshold for discriminating the frequency range to be removed.…”

“…By high range resolution, the information on the aircraft structure can be obtained from the HRRP. With high frequency resolution, the JEM [6][7][8][9][10][11], one of the microDoppler phenomena induced by a rotating jet engine compressor, can show its unique spectrum affected by several characteristics of the jet engine. Thus, an HRRP-JEM image composed of range and frequency axes is considered as an independent means for radar target recognition by localizing the equipped jet engine installed on the aircraft [5,6,12].…”

Analysis of Micro-Doppler Signatures from Rotating Propellers Using Modified HHT Method

“…본 논문에서는 납작한 PEC 평판으로 모델링된 프 로펠러 날개에 대하여 등가 전류법(Equivalent Current Method: ECM)을 이용해 변화하는 시간에 대하 여 얻은 산란파 데이터를 이용하였다 [3], [4] . 이러한 데 이터를 바탕으로 고해상도를 갖는 HHT(Hilbert Huang Transform) 기법 [5] 에 1차 주파수 성분 외의 고조 파 성분을 약화시키는 기법이 추가된 수정된 HHT 기법 [6] 을 활용하여 회전하는 프로펠러 날개에 의한 마이크로 도플러 신호를 해석하였다.…”

Efficient Classification of Low-Resolution Range Profiles of Automobiles Using a Combination of Useful Features

“…Among several radar signatures, the range profile (RP) shows the unique one dimensional distribution of the radar cross-section [2][3][4][5][6][7][8][9] of the automobile and can be effectively used for classification of automobiles which can contribute to anti-collision, lane-change, and automobile control regardless of weather and day-night conditions [10]. RP can also provide two-dimensional radar image of automobiles if the synthetic aperture radar (SAR) [11][12][13][14][15][16][17][18], the inverse SAR [19] and the jet engine modulation [20] techniques are applied.…”