Ferdjallah M, Barr R E
Electrical Engineering Department, University of Texas, Austin 78712.
IEEE Trans Biomed Eng. 1994 Jun;41(6):529-36. doi: 10.1109/10.293240.
This paper investigates adaptive digital notch filters for the elimination of powerline noise from biomedical signals. Since the distribution of the frequency variation of the powerline noise may or may not be centered at 60 Hz, three different adaptive digital notch filters are considered. For the first case, an adaptive FIR second-order digital notch filter is designed to track the center frequency variation. For the second case, the zeroes of an adaptive IIR second-order digital notch filter are fixed on the unit circle and the poles are adapted to find an optimum bandwidth to eliminate the noise to a pre-defined attenuation level. In the third case, both the poles and zeroes of the adaptive IIR second-order filter are adapted to track the center frequency variation within an optimum bandwidth. The adaptive process is considerably simplified by designing the notch filters by pole-zero placement on the unit circle using some suggested rules. A constrained least mean-squared (CLMS) algorithm is used for the adaptive process. To evaluate their performance, the three adaptive notch filters are applied to a powerline noise sample and to a noisy EEG as an illustration of a biomedical signal.
本文研究用于消除生物医学信号中电力线噪声的自适应数字陷波滤波器。由于电力线噪声频率变化的分布可能以60Hz为中心，也可能不以60Hz为中心，因此考虑了三种不同的自适应数字陷波滤波器。对于第一种情况，设计了一种自适应FIR二阶数字陷波滤波器来跟踪中心频率变化。对于第二种情况，自适应IIR二阶数字陷波滤波器的零点固定在单位圆上，极点进行调整以找到最佳带宽，从而将噪声消除到预定义的衰减水平。在第三种情况下，自适应IIR二阶滤波器的极点和零点都进行调整，以在最佳带宽内跟踪中心频率变化。通过使用一些建议的规则在单位圆上进行零极点配置来设计陷波滤波器，大大简化了自适应过程。自适应过程采用约束最小均方（CLMS）算法。为了评估它们的性能，将这三种自适应陷波滤波器应用于电力线噪声样本以及作为生物医学信号示例的带噪脑电图。
