As a discrete spectrum correction method, the Fourier transform （FT） continuous zoom analysis method is widely used in vibration signal analysis, but little effort had been made on this method＇s anti-noise performa...As a discrete spectrum correction method, the Fourier transform （FT） continuous zoom analysis method is widely used in vibration signal analysis, but little effort had been made on this method＇s anti-noise performance. It is widely believed that the analysis accuracy of the method can be substantially improved by increasing the zoom multiple, however, with the zoom multiple increases, the frequency estimation accuracy may decline sometimes in practices. Aiming at the problems above, this paper analyzes the sources of frequency estimation error when a harmonic signal mixed with and without noise is processed using the FT continuous zoom analysis. According to the characteristics that the local maximum of the zoom spectrum may be wrongly selected when the signal is corrupted with noise, the number of wrongly selected spectrum lines is deduced under different signal-to-noise ratio and local zoom multiple, and then the maximum frequency estimation error is given accordingly. The validity of the presented analysis is confirmed by simulations results. The frequency estimation accuracy of this method will not improve any more under the influence of noise, and there is a best zoom multiple, when the zoom multiple is larger than the best zoom multiple; the maximum frequency estimation error will fluctuate back and forth. The best zoom multiple curves under different signal-to-noise ratios given provide a theoretical basis for the choice of the appropriate zoom multiples of the FT continuous zoom analysis method in engineering applications.展开更多
Discrete fast Fourier transform （FFT） has been widely applied to signal spectral analysis and can figure out the entire bandwidth spectrum of a signal. However, the fine structure of high resolution spectrum in a na...Discrete fast Fourier transform （FFT） has been widely applied to signal spectral analysis and can figure out the entire bandwidth spectrum of a signal. However, the fine structure of high resolution spectrum in a narrow bandwidth is required in some applications. If regular FFT is still used to figure out the high resolution spectrum, it will result in addition of data and at last sharply increase of computation and storage. Therefore, FFT is inefficient and a new method must be put forward. In the paper, the principle of zoom FFT technique based on complex modulation, its application to development of SLF/ELF receiver and how to obtain high resolution spectrum using the new technique are introduced in detail and also the theoretical and test results are presented.展开更多
针对舰船辐射噪声低频线谱动态频率精细特征提取存在的频率分辨率低、瞬时频率跟踪性差、频率分析不够精细等问题,提出了一种基于移频频率细化瞬时自相关函数滤波的改进维格纳威利分布(Wigner Ville distribution,WVD)算法Z-FIR-WVD(zoo...针对舰船辐射噪声低频线谱动态频率精细特征提取存在的频率分辨率低、瞬时频率跟踪性差、频率分析不够精细等问题,提出了一种基于移频频率细化瞬时自相关函数滤波的改进维格纳威利分布(Wigner Ville distribution,WVD)算法Z-FIR-WVD(zoom-finite impulse response filter-WVD)。通过对移频降采样瞬时自相关函数在时域进行FIR(finite impulse response)滤波后的信号进行细化分析,可有效提高对WVD中多线谱交叉项干扰的抑制能力和频率分辨能力,实现对低频线谱动态精细特征的有效提取。仿真实验和实测信号验证结果表明,该算法在保持WVD频率聚集性的前提下,可有效抑制交叉项干扰,并实现对低频线谱的高频率分辨率动态分析,为舰船辐射噪声低频线谱动态频率精细特征提取问题提供了一种新的解决方法。展开更多
基金supported by National Natural Science Foundation of China (Grant No. 50875085, Grant No. 50605021, and Grant No. 51075150)Guangdong Provincial Natural Science Foundation of China (Grant No. 91510641010000320)
文摘As a discrete spectrum correction method, the Fourier transform （FT） continuous zoom analysis method is widely used in vibration signal analysis, but little effort had been made on this method＇s anti-noise performance. It is widely believed that the analysis accuracy of the method can be substantially improved by increasing the zoom multiple, however, with the zoom multiple increases, the frequency estimation accuracy may decline sometimes in practices. Aiming at the problems above, this paper analyzes the sources of frequency estimation error when a harmonic signal mixed with and without noise is processed using the FT continuous zoom analysis. According to the characteristics that the local maximum of the zoom spectrum may be wrongly selected when the signal is corrupted with noise, the number of wrongly selected spectrum lines is deduced under different signal-to-noise ratio and local zoom multiple, and then the maximum frequency estimation error is given accordingly. The validity of the presented analysis is confirmed by simulations results. The frequency estimation accuracy of this method will not improve any more under the influence of noise, and there is a best zoom multiple, when the zoom multiple is larger than the best zoom multiple; the maximum frequency estimation error will fluctuate back and forth. The best zoom multiple curves under different signal-to-noise ratios given provide a theoretical basis for the choice of the appropriate zoom multiples of the FT continuous zoom analysis method in engineering applications.
基金"The Study of ELF Receiver" from Ministry of Science and Technology (2001BA601B03-01-03).
文摘Discrete fast Fourier transform （FFT） has been widely applied to signal spectral analysis and can figure out the entire bandwidth spectrum of a signal. However, the fine structure of high resolution spectrum in a narrow bandwidth is required in some applications. If regular FFT is still used to figure out the high resolution spectrum, it will result in addition of data and at last sharply increase of computation and storage. Therefore, FFT is inefficient and a new method must be put forward. In the paper, the principle of zoom FFT technique based on complex modulation, its application to development of SLF/ELF receiver and how to obtain high resolution spectrum using the new technique are introduced in detail and also the theoretical and test results are presented.
