求翻译!关于时频分析与小波变换~原文转自英国物理学院

发布时间:2024-06-07 19:19 发布:上海旅游网

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2
ABSTRACT
In this paper we present a new methodology for computing a time-frequency map for non-stationary signals using the continuous wavelet transform (CWT). The conventional method of producing a time-frequency map using the Short Time Fourier Transform (STFT) limits the time-frequency resolution by a pre-defined window length.In contrast, the CWT method does not require pre-selecting a window length and does not have a fixed time-frequency resolution over the time-frequency space. The CWT
utilizes dilation and translation of a wavelet to produce a time-scale map. One scale encompasses a frequency band, and is inversely proportional to the time support of the dilated wavelet. Previous workers have converted a time-scale map into a time-frequency map by taking the center frequencies of each scale. We transform the time-scale map by taking the Fourier transform of the inverse CWT to produce a time-frequency map. Thus,a time-scale map is converted into a time-frequency map in which the amplitudes of andividual frequencies rather than frequency bands are represented. We refer to such a map as the time-frequency CWT (TFCWT).We validate our approach with a non-stationary synthetic example and compare the results with the STFT and a typical CWT spectrum. Two field examples illustrate that the TFCWT can potentially be utilized to detect frequency shadows caused by hydrocarbons and identify subtle stratigraphic features for reservoir characterization.

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