Synthetic aperture sonar point response for buried objects

Synthetic aperture sonar (SAS) has been shown to be capable of focussing images of objects buried in sand, even when the sonar is operated below the critical grazing angle. Because the high resolution and clutter rejection provided by SAS may be an essential component of a successful buried mine detection system, we have investigated the SAS point response of a buried object. We simulate SAS data for a buried target, including the variations in signal intensity and phase along the synthetic aperture caused by transmission into the sediment. The sediment attenuation reduces the effective synthetic aperture, degrading the resolution. In addition, the mismatch of the SAS matched filter to this data causes a reduction in resolution and a shift in apparent position. We investigate these effects for transmission by the refracted path and by surface roughness scattering below the critical angle