A New Approach To Construct Virtual Array With Increased Degrees Of Freedom For Moving Sparse Arrays

In this letter, a novel approach to construct virtual array is proposed by exploiting synthetic aperture technology and the concept of difference coarray for sparse arrays. First, we prove that the proposed method can increase the degrees of freedom (DOF) of an arbitrary moving sparse array threefold. Therefore, the maximal number of resolvable sources for direction-of-arrival (DOA) estimation is tripled as well. Furthermore, we prove that the difference coarray of synthetic arrays is a hole-free uniform linear array (ULA) if the difference coarray of original arrays is hole-free. Therefore, for ULA based DOA estimation methods, better performance can be achieved by fully employing all elements in the difference coarray of synthetic arrays. In addition, unlike the dilated nested array method, which enlarges the intersensor spacing of nested arrays threefold to triple DOF, the proposed method does not need to increase array aperture physically. Thus it is more practical to mount a sensor array on a moving platform when taking space limitation into consideration. Simulation results are given to demonstrate the superiority of the proposed method.