WDA相关法时间延迟估计

相控阵超声检测中,相关法时间延迟估计是实现自适应聚焦的关键技术之一。为了消除噪声、模板窗口大小和缺陷特征等因素对相关法时间延迟估计的影响,结合检测超声回波信号的特点,提出了基于小波变换的相关法时间延迟估计方法。理论仿真和实验均证明该方法能有效抑制上述因素的影响,提高时间延迟估计精度。仿真计算表明:在可信度为0.95的情况下,信噪比提高了3.2dB,最小窗口大小从无穷大变成了3倍于探头中心频率对应周期,模板有效范围扩展了60%。

Time delay estimation using WDA cross-correlation

Time delay estimation using cross-correlation method is a key technology for adaptive focusing in phased array ultrasound testing. The WDA (acronym of Wavelet, Detail and Approximate) cross-correlation method based on wavelet transform was developed in consideration of measuring ultrasound echo signals to reduce the effects of noise, template window sizes and flaws on the time delay estimate using cross-correlation methods. Simulations and experiments show that the method effectively reduces these effects and improves the time delay estimation precision. The simulation result also shows that for a reliability of 0.95, the signal to noise ratio is improved by 3.2 dB, the minimal window size is reduced from infinity to 3 times the period corresponding to the probe center frequency, and the template effective range is extended by 60% compared with the conventional cross-correlation method.