Ata O W, Fish P J
School of Electronic Engineering Science, University of Wales, Bangor, UK.
Ultrasonics. 1991 Sep;29(5):395-403. doi: 10.1016/0041-624x(91)90092-m.
Deviation from plane wave conditions within the ultrasound beam of a Doppler blood flow detector leads to a non-linear relationship between the phase angle of the back-scattered signal and the scatterer position. This in turn leads to frequency modulation of the Doppler signal and an increase in the Doppler spectrum width. The relationship between the ultrasound beam and the observed signal spectrum has been investigated by employing a computer-based model of the ultrasound field which enabled the calculation of: 1, pressure (amplitude and phase angle) field distributions from plane disc and focused transducers with unapodized and apodized aperture field distributions; 2, the Doppler signal from a scatterer moving through the field; and 3, the spectrum of this signal. The increase in spectral width resulting from deviations from plane wave conditions was calculated by comparing this spectrum with that of the signal from which frequency modulation had been removed.
多普勒血流探测器超声束内偏离平面波条件会导致背向散射信号的相位角与散射体位置之间呈非线性关系。这进而会导致多普勒信号的频率调制以及多普勒频谱宽度增加。通过使用基于计算机的超声场模型，研究了超声束与观测信号频谱之间的关系，该模型能够计算：1. 具有未加窗和加窗孔径场分布的平面圆盘和聚焦换能器的压力（幅度和相位角）场分布；2. 散射体在场中移动产生的多普勒信号；3. 该信号的频谱。通过将该频谱与去除了频率调制的信号频谱进行比较，计算了因偏离平面波条件而导致的频谱宽度增加。
