Robust Chinese Remainder Theorem–Based Synthetic Aperture Sonar Motion Estimation

Motion estimation is required to obtain high imaging quality in synthetic aperture sonars (SASs). Displaced phase center antenna (DPCA) micronavigation is an important technique of motion estimation in SASs. A key step in DPCA micronavigation is accurately determining the time delay between echoes received by the approximate "phase center" array between adjacent pings. Unfortunately, the accuracy of the existing method for estimating this time delay is often deteriorated by the ambiguity of the time delay estimates in the presence of noise or interference. This article proposes an accurate method of estimating the time delay based on the Robust Chinese Remainder Theorem (RCRT). The experimental results show that the proposed method decreases the ambiguous rate of time delay estimates by one order of magnitude, compared to the conventional approach, which means the estimation accuracy is improved significantly. The SAS imaging results demonstrate that the RCRT-based motion estimation helps to obtain higher-quality images.