Coherence beamforming applied to velocity estimation and partially coherent signals
Coherence beamforming applied to velocity estimation and partially coherent signals
复制标题
相干波束成形应用于速度估计和部分相干信号
DOI：
10.1109/ultsym.2015.0013
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
J. Doherty
中科院分区：
文献类型：
--
作者：
J. Dahl;Y. Li;D. Hyun;J. Doherty
时延和相移估计器常被用于跟踪散斑信号，以便估计诸如应变、位移和速度等参数。这些估计器依靠波束形成的射频信号来准确估计时间和相移。然而，像散斑这样的部分相干目标会在估计中引入方差和偏差误差，因为延迟求和波束形成器不能适应采样波形的空间变化。此外，声学和热噪声的存在会使这个问题恶化。我们引入一种方法，当波束形成器应用于速度和位移估计时，对其使用的信息进行修改。通过模拟，使用卡萨伊和卢帕斯的自相关方法在射频通道信号之间而不是波束形成的射频信号之间估计速度。从那些表现出高相关性的通道信号对中估计速度和位移。通过在卡萨伊和卢帕斯的速度估计器中消除不相干信息，在高噪声环境中减少了抖动。例如，在通道信号中相对于血液为0分贝噪声的情况下，将信号限制为高相干信号（例如10个空间滞后），使卡萨伊速度估计器中的抖动从大约6.0毫米/秒减少到2.5毫米/秒。一般来说，随着越来越多的不相干信息添加到波束形成的信号中，抖动会增加，并且低噪声会产生更小的抖动。
Time-delay and phase-shift estimators are often used to track speckle signals in order to estimate parameters such as strain, displacement, and velocity. These estimators rely on the beamformed RF signal to accurately estimate time and phase shifts. Partially coherent targets such as speckle, however, introduce variance and bias errors into the estimation because the delay-and-sum beamformer does not adapt to the spatial variation of the sampled waveform. In addition, the presence of acoustic and thermal noise can exacerbate this problem. We introduce a method that modifies the information used by the beamformer when it is applied to velocity and displacement estimation. Using simulations, velocity was estimated between RF channel signals, rather than beamformed RF signals, using Kasai's and Loupas' autocorrelation methods. Velocity and displacement was estimated from those channel signal pairs that exhibited high correlation. By eliminating incoherent information in Kasai's and Loupas' velocity estimators, jitter was reduced in high noise environments. For example, at 0 dB noise relative to the blood in the channel signals, Limiting the signal to high coherence signals (e.g. 10 spatial lags) reduced the jitter in the Kasai velocity estimator from approximately 6.0 mm/s to 2.5 mm/s. In general, jitter increased with increasingly incoherent information added into the beamformed signal and low noise yielded smaller jitter.