A DEMON Line Spectrum Detection Method Based on Parameter Pre-Estimation

A detection of envelope modulation on noise (DEMON) method based on parameter pre-estimation (PE-DEMON) is proposed according to the model of multiple composite hypothesis testing. In the PE-DEMON method, the coupling mechanism between the line spectrum detection and shaft frequency estimation is designed using the harmonic characteristics of the DEMON line spectrum. In the process of PE-DEMON, several prior distribution of the shaft frequency is supposed and the spectrum analysis is performed, then pre-detection of the line spectrum and pre-estimation of the shaft frequency is made based on the spectrum data. The current distribution information of the shaft frequency is modified by the output of the pre-estimator. Spectral analysis is performed again using the modified distribution information of the shaft frequency, and the line spectrum detection and the shaft frequency estimation is carried out again to obtain the final output. The simulated data and the measured propeller noise data analysis show that the PE-DEMON method can improve the estimation accuracy of the shaft frequency and the detection probability of line spectrum compared with the traditional DEMON method.