Wen Y, Qian M, Gong X, Zhen B, Wan M
Dept of Biomedical Engineering, Xi'an Jiaotong University.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi. 1997 Mar;14(1):15-20.
A high-pass filter is used to remove the large signals scattered or reflected from stationary and slow moving objects in many clinical CW Doppler units. theoretical results are presented that such a filter will lead to overestimate of the mean velocity of Doppler blood flow. As for different frequency signals, high-pass filter have different amplitudes and phase responses, consequently, nonlinear phase shift is produced. It is proved by computer experiment that nonlinear phase shift caused by high-pass filter hardly has any effects on Doppler flow power spectrum if the high-pass filter does not affect the amplitudes of signals.
在许多临床连续波多普勒设备中，高通滤波器用于去除从静止和缓慢移动物体散射或反射的大信号。理论结果表明，这种滤波器会导致对多普勒血流平均速度的高估。对于不同频率的信号，高通滤波器具有不同的幅度和相位响应，因此会产生非线性相位偏移。计算机实验证明，如果高通滤波器不影响信号幅度，由其引起的非线性相位偏移对多普勒血流功率谱几乎没有任何影响。
