超外差接收相敏检波在电磁超声检测中的应用

Application of super-heterodyne phase-sensitive detector in electromagnetic acoustic testing

为了提高电磁超声检测接收信号的信噪比,研究和设计了基于超外差接收正交相敏检波技术的电磁超声检测系统.应用该系统分别对铝合金、碳钢和不锈钢试样进行了检测,对接收信号进行了正交相敏检波处理,将处理后的信号同原始接收射频信号进行了对比,分析了中频放大器和相敏检波器中低通滤波器的带宽设置对检测结果的影响.研究结果表明:超外差接收正交相敏检波技术在铝合金、碳钢和不锈钢等非铁磁性或铁磁性金属材料的电磁超声检测中可以起到去噪、提高信噪比的作用.

In order to increase the signal-to-noise ratio of the electromagnetic acoustic received signal,an electromagnetic acoustic inspection system based on super-heterodyne receiver orthogonal phase-sensitive detection technique was designed and applied to inspect samples of aluminum,carbon steel and stainless steels.The received signal after being processed with the orthogonal phase-sensitive detection technology was compared with the received original radio frequency signal.The effects on the testing results of bandwidth settings in the intermediate frequency（IF） amplifier and the low-pass filter of phase-sensitive detector were analyzed.The results show that the application of orthogonal phase-sensitive detection technology in the inspection of aluminum alloy,carbon and stainless steels non-ferromagnetic or ferromagnetic metal materials can denoise from the received signal and increase the signal-to-noise ratio.