Novel direction finding algorithm based on phase locked loop with low computational complexity

Radio Direction Finding (DF) is a technique that identifies the bearing angle or the coordinates of an incoming radio signal(s). In this paper, we propose a method for Direction of Arrival (DOA) estimation with low computational complexity that is based on the differential phase of signal received by an M-element uniform circular antenna array with a commutative switch followed by single channel Software Defined Radio (SDR) receiver. This method utilizes a bank of Phase Locked Loops (PLLs) to estimate the phase values at each antenna element. These estimated phase values are then fed into a signal processing block that estimates the DOA of the received signal. Analysis of the challenges of computational complexity in this algorithm is presented. One important factor when using phase locked loop is the small convergence rate of the algorithm compared to the switching cycle. In order to achieve small convergence rate, we also propose an improvement for reducing computational complexity. The simulation results for DOA estimation using the proposed structure are shown to verify the performance of the system.