The simulation for ultrasonic testing based on frequency-phase coded excitation

Large time-bandwidth product coded signal and pulse compression are introduced into ultrasonic testing. Linear frequency modulation (LFM) excitation is usually used to improve time resolution, but sidelobe should be suppressed to detect smaller flaws nearby. Barker coded excitation is usually used to suppress sidelobe, but time resolution of results is lower than LFM excitation. So frequency-phase coded excitation is proposed to obtain higher time resolution and lower sidelobe level. The proposed excitation signal is applying LFM to each sub-pulse of Barker code, and it is called LFM-B13. The results of simulations demonstrate that, time resolution of LFM-B13 excitation is approximately 40% higher than that of LFM excitation, and main sidelobe level of LFM-B13 excitation is approximately 4 dB lower than that of LFM excitation, when 60% bandwidth of 5 MHz central frequency transducers are used. Copyright © 2019 Inderscience Enterprises Ltd.