Underdetermined Direction-of-Arrival Estimation Using Sparse Circular Arrays on a Rotating Platform

In this letter, we propose to exploit the array motion of sparse circular arrays (SCA) on a rotating platform to increase the degrees of freedom (DOF) (i.e. the number of unique spatial lags) associated with the rotating array when compared to the array on a fixed platform. This increases the total number of sources that can be resolved by the rotating SCA with the same amount of physical sensors. The signal model for the combined synthetic array before and after a unit rotation motion is derived together with the closed-form expression for the increase in the DOF of a rotating nested sparse circular array (NSCA). A new modified NSCA is proposed and it is shown that the DOF of the proposed sparse array is higher than the conventional NSCA under motion with the same number of sensors. A simulation study is carried out to estimate the direction of arrival (DOA) of signals in a sensing environment that is assumed to be stationary over array motion of unit rotation and it verifies the effectiveness of array motion to increase the DOF of an SCA. The simulations also show the improved performance of the proposed NSCA.