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首页> 外文期刊>IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control >Interpolation methods for time-delay estimation using cross-correlation method for blood velocity measurement
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Interpolation methods for time-delay estimation using cross-correlation method for blood velocity measurement

机译：使用互相关法进行血流速度测量的插值方法

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摘要

The cross-correlation method (CCM) for blood flow velocity measurement using Doppler ultrasound is based on time delay estimation of echoes from pulse-to-pulse. The sampling frequency of the received signal is usually kept as low as possible in order to reduce computational complexity, and the peak in the correlation function is found by interpolating the correlation function. The parabolic-fit interpolation method introduces a bias at low sampling rate to the ultrasound center frequency ratio. In this study, four different methods are suggested to improve the estimation accuracy: (1) Parabolic interpolation with bias-compensation, derived from a theoretical signal model. (2) Parabolic interpolation combined with linear filter interpolation of the correlation function. (3) Parabolic interpolation to the complex correlation function envelope. (4) Matched filter interpolation applied to the correlation function. The new interpolation methods are analyzed both by computer simulated signals and RF-signals recorded from a patient with time delay larger than 1/f/sub 0/, where f/sub 0/ is the center frequency. The simulation results show that these methods are more accurate than the parabolic-fit method. From the simulation, the worst estimation accuracy is about 1.25% of 1/f/sub 0/ for the parabolic-fit interpolation, and it is improved by the above methods to less than 0.5% of 1/f/sub 0/ when the sampling rate is 10 MHz, the center frequency is 2.5 MHz and the bandwidth is 1 MHz. This improvement also can be observed in the experimental data. Furthermore, the matched filter interpolation gives the best performance when signal-to-noise ratio (SNR) is low. This is verified both by simulation and experimentation.
机译：使用多普勒超声测量血流速度的互相关方法（CCM）基于脉冲间回波的时延估计。为了降低计算复杂度，通常将接收信号的采样频率保持得尽可能低，并且通过对相关函数进行内插来找到相关函数中的峰值。抛物线拟合插值法将低采样率的偏差引入超声中心频率比。在这项研究中，提出了四种不同的方法来提高估计精度：（1）从理论信号模型推导的具有偏差补偿的抛物线插值。 （2）抛物线插值与线性滤波器插值相结合的相关函数。 （3）抛物线插值到复相关函数包络。 （4）将匹配滤波器插值应用于相关函数。通过计算机模拟信号和从患者那里记录的RF信号（时间延迟大于1 / f / sub 0 /，其中f / sub 0 /是中心频率）对新的插值方法进行了分析。仿真结果表明，这些方法比抛物线拟合法更准确。从仿真中可以看出，抛物线拟合插值的最差估计精度约为1 / f / sub 0 /的1.25％，通过上述方法可以将其提高到小于1 / f / sub 0 /的0.5％。采样率为10 MHz，中心频率为2.5 MHz，带宽为1 MHz。在实验数据中也可以观察到这种改善。此外，当信噪比（SNR）低时，匹配的滤波器插值可提供最佳性能。仿真和实验均证实了这一点。

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