A FUNDAMENTAL LIMIT ON DELAY ESTIMATION USING PARTIALLY CORRELATED SPECKLE SIGNALS
A FUNDAMENTAL LIMIT ON DELAY ESTIMATION USING PARTIALLY CORRELATED SPECKLE SIGNALS
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DOI：
10.1109/58.365243
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发表时间：
1995-03-01
影响因子：
3.6
通讯作者：
TRAHEY, GE
中科院分区：
文献类型：
--
作者：
WALKER, WF;TRAHEY, GE
在超声成像中使用延迟估计来估计血液或软组织运动，测量回波到达时间差以进行相位畸变校正，以及估计位移以进行组织弹性测量。在这些应用中的每一个中，使用相对于彼此至少部分去相关的散斑信号来执行延迟估计。利用这种数据的延迟估计受到称为假峰的大误差和称为抖动的较小幅度误差的影响。虽然有时可以通过非线性处理去除假峰，但抖动误差对延迟估计技术的性能造成了根本限制。本文应用Cramer-Rao下限推导出一个解析表达式，预测抖动误差的大小时，估计延迟使用射频（RF）数据从斑点目标。所提出的解析表达式包括由于物理过程，电子噪声的腐败，和一些其他因素的信号去相关的影响。仿真结果表明，归一化互相关算法的性能接近理论预测。这些结果表明，对于较差的信噪比（0 dB），信噪比的小幅改善可以显著降低抖动幅度。在高信噪比（30 dB）下，少量的信号去相关可以显著增加抖动误差的幅度。
Delay estimation is used in ultrasonic imaging to estimate blood or soft tissue motion, to measure echo arrival time differences for phase aberration correction, and to estimate displacement for tissue elasticity measurements. In each of these applications delay estimation is performed using speckle signals which are at least partially decorrelated relative to one another. Delay estimates which utilize such data are subject to large errors known as false peaks and smaller magnitude errors known as jitter. While false peaks can sometimes be removed through nonlinear processing, jitter errors place a fundamental limit on the performance of delay estimation techniques. This paper applies the Cramer-Rao Lower Bound to derive an analytical expression which predicts the magnitude of jitter errors incurred when estimating delays using radio frequency (RF) data from speckle targets. The analytical expression presented includes the effects of signal decorrelation due to physical processes, corruption by electronic noise, and a number of other factors. Simulation results are presented which show that the performance of the normalized cross correlation algorithm closely matches theoretical predictions. These results indicate that for poor signal to noise ratios (O dB) a small improvement in signal to noise ratio can dramatically reduce jitter magnitude. At high signal to noise ratios (30 dB) small amounts of signal decorrelation can significantly increase the magnitude of jitter errors.