A Method to Quantitatively Evaluate the Phase Error of SAS PTRS

Point target reference spectrum (PTRS) plays an important role in synthetic aperture sonar (SAS) imagery. In the past, the accuracy of PTRS was often evaluated using peak sidelobe ratio (PSLR), integration sidelobe ratio (ISLR) and resolution after synthetic aperture image formation. In general, this evaluation is time consuming. In this paper, a phase error method is exploited to evaluate the accuracy of PTRS. Considering the fact that there is no analytical point of stationary phase with respect to two-way slant range of multireceiver SAS system, the numerical method is exploited to calculate the point of stationary phase. Subsequently, the PTRS used as the criteria to evaluate other approximate PTRS is obtained. This paper takes the PTRS based on equivalent transformation of radical expression as an example. The simulations show that the presented method can well evaluate the PTRS before focusing. This results in time and cost savings.