The spectrum of amplitude modulated signal are two half magnitude spectrums of base band signal positive and negative shifted by a carrier or R. F. frequency.

调幅讯号之频谱为一半强度基频讯号之频谱分别正负位移一射频或载波之频率。

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The circular region F-norms in low frequency band of wavelet transform is used as color feature of the image and the energy ratio of high frequency band is used to form texture descriptor.

颜色特征采用整数小波低频系数矩阵中环形区域的F -范数，纹理特征则采用高频部分的能量比值。

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