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介绍了一种改进的数字全通滤波器的设计方法。该方法是基于复倒谱和平稳最小相位序列之间的关系提出的。通过使全通滤波器传递函数分母的群延迟在加权最小均方意义下近似理想的群延迟,导出复倒谱的计算公式。根据得到的复倒谱,利用复倒谱与最小相位序列之间的关系可以计算出全通的分母系数。由全通的特性已知,分母系数可以完全决定全通的传递函数。这种改进的方法能够使所设计滤波器的群延迟特性在整个频率范围内近似理想的群延迟特性。
An improved design method of digital all-pass filter is introduced. The method is based on the relationship between complex cepstrum and stationary minimum phase sequence. The formula of complex cepstrum is deduced by making the group delay of all-pass filter denominator approximate the ideal group delay in the sense of weighted least mean square. According to the obtained complex cepstrum, the total denominator coefficient can be calculated by using the relationship between complex cepstrum and minimum phase sequence. It is known from the all-pass feature that the denominator coefficient can completely determine the all-pass transfer function. The improved method can make the group delay of the designed filter approximate the ideal group delay in the whole frequency range.