Direction-of-arrival (DOA) tracking using improved direction lock loop with real-time bias correction for antenna array based GNSS receivers

For the antenna array based Global Navigation Satellite Systems (GNSS) receivers on a moving platform, the direction lock loop is a simple and effective method to achieve direction-of-arrival (DOA) tracking of GNSS signals. However, the discriminators used in the direction lock loop will introduce a noticeable DOA tracking bias when the true DOA is not zero. To solve this problem, an improved direction lock loop with real-time bias correction, which is independent of antenna array parameters, is proposed to achieve an unbiased DOA tracking in this paper. Then, three discriminators including coherent real part method, non-coherent amplitude method and non-coherent power method, are theoretically discussed, and further compared in terms of the output curve, convergence range, gain, mean square error (MSE). Finally, several typical simulation scenarios are designed for verifying the proposed method in accordance with the effects of DOA tracking with and without bias correction. Simulation results show that the proposed method can effectively track the signal DOA and significantly decrease the DOA tracking bias under different scenarios.