若采样长度与回转速度不吻合，将会出现伪周期，使主值函数项中提取周期成分后的信号失实。

If sampling length doesn't adapt rotative velocity, the results of calculation by FFT or periodogram analysis will lead to pseudo-periods, which distorts the principal value function terms.

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而传统的延拓方法在前后两个边界处都会产生伪边缘，并且在延拓时还需考虑滤波器系数长度的奇偶性。

But traditional border processing methods will cause false edges, and also should consider the parity of filter coefficient.

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