Application of linear frequency modulation pulse compression in air-coupled ultrasonic testing

Effective signal processing technology should be used to improve signal-to-noise ratio in air-coupled ultrasonic testing, because of there is feeble signal and low signal-to-noise ratio. Pulse compression of linear frequency modulation could enhance system´s signal to noise ratio and distance resolution effectively. Principle of linear frequency modulation pulse compression is introduced, including of designing and accomplishing of matching filter. The relationship between pulse compression parameters and testing result is analyzed. The affect of exciting mode to ultrasonic signal and pulse compression to signal-to-noise ratio are researched by comparing experiment results. Air-coupled ultrasonic C-scan testing system based on pulse compression is accomplished, and the effectiveness of pulse compression method is testified by ultrasonic imaging results.