Ider Y Z, Köymen H
Department of Electrical and Electronic Engineering, Middle East Technical University, Ankara, Turkey.
IEEE Trans Biomed Eng. 1990 Jun;37(6):624-31. doi: 10.1109/10.55666.
It has been reported that power line frequency must be accurately known if line interference is to be accurately subtracted from the output of a bipotential amplifier. In this paper, hardware developed to record the common mode line frequency signal on the body simultaneously with the ECG lead signals of a 15-channel computerized cardiograph is described. This interference reference signal and its quadrature, obtained by software, are linearly combined to be subtracted from any one of the channels to reduce line interference to below the quantization level of the 12 b A/D converter. Coefficients of the linear combination are estimated using linear regression which is applied to the relatively isoelectric regions of the data, excluding the QRS complexes. Since the interference reference signal is available in real time, simultaneously with the ECG signals, another software approach is also adopted in which an adaptive interference reduction algorithm is used to cope with varying interference. A recursive least squares algorithm with forgetting factor is used to update the coefficients. This updating mechanism is gated by the output of a software QRS detector. Results regarding the performance of both the off-line and the adaptive algorithms are given, and the effects of nonisoelectric portions of the ECG lead signals on the estimation of the coefficients are quantified.
据报道，如果要从双电位放大器的输出中准确减去线路干扰，就必须准确知道电源线路频率。本文描述了一种硬件，它能在记录15通道计算机心电图仪的心电图导联信号的同时，记录身体上的共模线路频率信号。通过软件获得的该干扰参考信号及其正交信号进行线性组合，然后从任何一个通道中减去，以将线路干扰降低到12位A/D转换器的量化水平以下。使用线性回归估计线性组合的系数，该回归应用于数据的相对等电位区域，不包括QRS复合波。由于干扰参考信号与心电图信号同时实时可用，因此还采用了另一种软件方法，即使用自适应干扰减少算法来应对变化的干扰。使用带有遗忘因子的递归最小二乘算法来更新系数。这种更新机制由软件QRS检测器的输出控制。给出了离线算法和自适应算法的性能结果，并量化了心电图导联信号的非等电位部分对系数估计的影响。
