A Search-free DOA Estimation Algorithm for Coprime Arrays

In this paper, we propose a fast search-free method for direction-of-arrival (DOA) estimation with coprime arrays. A coprime array consists of two uniform linear subarrays with inter-element spacings $M\lambda/2$ and $N\lambda/2$, where $M$ and $N$ are coprime integers and $\lambda$ is the wavelength of the signal. Because uniform linear arrays enjoy many processing advantages over arbitrary geometry arrays, our strategy is to exploit the uniform linear structure of the subarrays in coprime arrays. We first estimate the DOA's for each uniform linear subarray separately and then combine the two estimates from the two subarrays. For combining the two estimates, we propose a method that projects the estimated point in the two-dimensional plane onto one-dimensional line segments that correspond to the entire angular domain. By doing so, we avoid the search step and consequently, we greatly reduce the computational complexity of the method.