中文摘要：

为了提高空气耦合超声检测中的信号强度及其信噪比,研究线性调频脉冲压缩技术在空气耦合超声检测中的应用。介绍线性调频脉冲压缩技术的基本原理及其匹配滤波器的设计与实现,分析脉冲压缩参数对空气耦合超声检测结果的影响,试验研究不同激励方式对空气耦合超声换能器接收信号的影响以及脉冲压缩方法对提高信噪比的实际效果,构建空气耦合超声C扫描检测系统,对碳纤维增强复合材料板进行检测试验。研究结果表明：相对于常规脉冲激励方式,连续波激励方式可提高换能器的能量转换效率,激励信号频率特性与换能器频率特性相一致时效果最佳;应用线性调频脉冲压缩方法后,空气耦合超声检测的信噪比有了明显提高,检测效果得到了明显改善。

英文摘要：

To increase the signal and the signal-to-noise ratio in air-coupled ultrasonic testing,a study of application of linear-frequency-modulation based pulse compression technology in air-coupled ultrasonic testing is carried out.The fundamentals of linear-frequency-modulation based pulse compression technology are introduced.The design and implementation procedure of matched filter is described.The relationship between parameters of pulse compression technology and the test results is analyzed.Experimental researches on the influences of different excitation modes on the received signal of air-coupled ultrasonic transducer and the actual effect of pulse compression technology on the improvement of signal-to-noise ratio are carried out.An air-coupled ultrasonic C-scan testing system is set up with pulse compression technology and test experiments are done with carbon fiber reinforced plastics（CFRP） plates.Experimental results show that the transducer＇s energy conversion efficiency with continuous wave excitation is better than that with pulse wave excitation,especially when the frequency characteristic of excitation signal is same as that of the transducer.The signal-to-noise ratio of air-coupled ultrasonic testing is enhanced effectively with pulse compression technology,and the validity of pulse compression technology is testified by ultrasonic imaging results.