Underground Sonar Using Shear Waves ‐Resolution improvement Using Pulse Compression and Dynamic Focusing‐

In order to detect the buried relics and ruins at shallow depth, a method by using shear waves has proposed. The effect of the pulse compression processing is examined for improving the underground imaging resolution. Using a super‐magnetostriction vibrator which can change waveforms and use high frequency waves, we generate both chirp waves and high frequency waves. To confirm the resolution of underground images, pulse compression is simulated. And, to confirm the lateral resolution, dynamic focusing is simulated in our laboratory. Then, its exploration experiment is carried out where the buried position has already known. The axial resolutions are smaller than 0.2m when the range of start and stop frequencies are more than 700Hz in the simulation. And the underground images obtained from exploration experiment confirm that the images by the pulse compression have almost the same axial resolution as by the result of the simulation.