The methods of time frequency analysis include linear, quadratic and adaptive methods. They provide effective tools for analyzing signal time varying spectrum in time frequency plane.

时频分析方法分为线性、二次型和自适应等多种方法，它们提供了在时频二维平面上，分析信号时变功率谱的有效手段。

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With a phase grating located at Fourier frequency plane, optical image subtraction is obtained as a result of the coherent superposition of the zeroth and the first order of the diffracted light.

置一位相光栅于相干光学处理系统频谱平面，利用其零级与一级衍射光的相干迭加实现图象相减。

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It stems from the concept of instantaneous frequency, and it can describe accurately the local properties of dynamic data in the time-frequency plane.

该方法源于瞬时频率的概念，它能把动态信号的局部特征正确地在时频域内予以描述。

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