Optimized Design for Sparse Cross Arrays in Both Near-Field and Far-Field

Two-dimensional arrays are required to generate 3-D acoustic images in both near-field and far-field regions. However, almost all of the sparse methods, which decrease the number of elements, only synthesize the 2-D sparse arrays in far-field conditions. In this paper, a novel method is proposed for optimizing sparse array in both near-field and far-field conditions that improving the sparseness of the optimized array. First, a new energy function is proposed and successfully synthesizes sparse arrays in both near-field and far-field conditions. The simplified form of the new energy function is then presented for cutting down computational load during optimization process. Second, the nongrid sparse array technology, which connotes irregular element positioning, is introduced into the simulated annealing algorithm to extensively reduce the number of active elements. Finally, the optimized method is demonstrated through designing a cross array with 100 + 100 elements. The results show notable improvements on the array characteristics in random working distances over those reported in the literature.