Pedersen P C, Grebe A
Department of Electrical and Computer Engineering, Worcester Polytechnic Institute, MA 01609, USA.
Ultrasonics. 2001 Mar;39(2):101-8. doi: 10.1016/s0041-624x(00)00044-5.
This paper describes the design and performance of an ultrasound measurement system, utilizing a swept frequency excitation signal, for analyzing the backscattered signal from planar rough surfaces. The implementation is in the form of a time delay spectrometry (TDS) system operating in reflection mode whose advantages are improved signal-to-noise ratio even with low peak power relative to conventional pulse-echo methods. Because of simultaneous transmission and reception, the TDS system requires two transducers. The TDS measurement system uses a swept frequency spectrum analyzer as the central analog processing unit. Both planar piston and focused transducers in the low MHz range were used for the measurements. Due to the statistical nature of rough surface backscatter, the mean of several statistically uncorrelated measurements is required to characterize the scattering behavior of a given rough surface. Backscatter data are obtained for a series of planar rough surfaces, in the form of scattering magnitude vs. frequency and vs. incident (=backscattered) angle. Analysis of the results reveals a good correlation between the root-mean-square (RMS) height and mean backscatter magnitude at 0 degrees incident angle, and between the ratio of RMS height to correlation length and the difference in mean backscatter magnitude between 0 degrees and 5 degrees.
本文描述了一种利用扫频激励信号来分析平面粗糙表面后向散射信号的超声测量系统的设计与性能。该系统采用反射模式下的时延谱法（TDS）实现，其优点是即使在峰值功率较低的情况下，相对于传统脉冲回波方法，信噪比也有所提高。由于同时进行发射和接收，TDS系统需要两个换能器。TDS测量系统使用扫频频谱分析仪作为中央模拟处理单元。测量中使用了低兆赫兹范围内的平面活塞式换能器和聚焦换能器。由于粗糙表面后向散射的统计特性，需要对几个统计不相关的测量值求平均值，以表征给定粗糙表面的散射行为。针对一系列平面粗糙表面获取了后向散射数据，其形式为散射幅度与频率以及与入射（=后向散射）角度的关系。结果分析表明，在0度入射角时，均方根（RMS）高度与平均后向散射幅度之间，以及RMS高度与相关长度之比和0度与5度之间平均后向散射幅度之差之间存在良好的相关性。
