The time-frequency plane of a standard OFDM system is a rectangular grid.

标准OFDM系统设计的时-频面为矩形网格。

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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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The concept of local energy in time-frequency plane, based on local wave theory, is defined. Then a new feature extraction method based on the local energy in time-frequency plane is given.

在局域波理论的基础上，引入了时频局部能量的概念，进而提出了一种基于时频局部能量的特征提取方法。

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