全相位自适应滤波器设计

文中首先给出了全相位滤波器结构，并理论分析得到等效的FIR滤波器模型和满足线性相位的条件，全相位滤波器具有明确的传输特性，且通带及阻带内的波动基本消除，易于设计形成严格子带互补的滤波器组。对加噪信号进行N次全相位频谱归一化处理，并递归设置幅值为1的频点而形成完整的传输特性，噪声的判断通过单次谱分析和全相位谱分析均值和方差特性来进行。实验中，对于淹没在强噪声中的信号进行了全相位自适应滤波，结果表明，对于整数倍的频率分辨率信号可以100%无失真恢复。全相位自适应滤波得到的信号提高0.8dB左右，通过提高滤波器阶数N或进行频谱校正可以进一步提高恢复信号质量。 

Design of Adaptive All-phase Filter

In this paper all-phase digital filter with double windows in frequency domain is presented first, through theoretically analyzing, then the according FIR system and the condition for linear phrase are given, which has apparent transmission property and waves in pass or stop band basically disappear, and it’s easily to make complementary sub band filter bank using all-phase filter. Signals added by noise are processed N times in the all-phase spectrum normalization way. It is recursively to set frequency point with amplitude 1 so to form the whole transmission property H. Noise is judged by the mean and variance of single and all-phase spectrum analysis. In the test, the drowned signals in the noise are processed using all-phase adaptive filter. The result verifies that signals with frequency by n times of spectrum resolution can be recovered 100% without lost. Signal quality are improved by 0.8dB, which can be further raised by means of increasing N or correcting spectrum.