摘要
为了消除由超声频率下移所引起的血流速度估计精度的下降,提出了一种基于回波频率跟踪的正交解调方法。首先建立了回波中心频率随深度下移的线性模型;然后使用传统I/Q(Inphase/Quadrature)解调方法得到有偏的基带信号,采用自相关方法沿深度方向分段估计中心频率的下移量,并利用估计出的这些值对所建立的线性模型进行拟合;最后利用拟合后的模型来实时跟踪回波的中心频率,并将其作为参考频率再进行I/Q解调。仿真和试验结果表明,基于回波频率跟踪的正交解调方法能够得到近似无偏的基带信号,提高血流速度估计的准确度和精度,改善彩色超声血流成像的质量。
A quadrature demodulation method based on echo-frequency tracking is proposed to eliminate the flow velocity estimation error caused by ultrasound frequency downshift. First a linear model is established for the central frequency downshift along depth direction. Then the frequency downshifts along depth are estimated through autocorre- lation technique based on the biased base-band signal obtained by conventional I/Q （Inphase/Quadrature） demodulation, and the estimated values are used for fitting the linear model. Finally the central frequencies are tracked by the fitted model, and used as the reference frequencies for I/Q demodulation. Simulation and experimental results show that nearly unbiased base-band signal can be obtained by the proposed demodulation method, so that the flow velocity estimation can be more accurate and the quality of ultrasound color flow imaging can be improved.
出处
《声学学报》
EI
CSCD
北大核心
2008年第3期262-267,共6页
Acta Acustica
