DOA tracking using an improved direction lock loop based on a three-element L-shaped array

Direction Lock Loop (DiLL) utilizes the direction of arrival (DOA) error obtained from the spatial correlation characteristics of the array antenna beamforming and dynamically adjusts the estimated DOA value through a closed-angle tracking loop. DiLL is a representative DOA tracking method for a direct sequence code division multiple access (DS-CDMA) system. Nevertheless, several issues prohibit employing DiLL in a global navigation satellite system (GNSS), such as limited tracking range, dead-zone effect, and separation of the capturing and tracking process. To solve these problems, we propose an improved DiLL tracking scheme based on a three-element L-shaped array named 3L-DiLL. The developed method exploits the 90-degree angular difference that naturally exists in the L-shaped array response of the normalized spatial correlation function and obtains the angular difference between the estimated and the true DOA to realize real-time DOA tracking of the target signal. Considering an incident signal of -180to+180∘\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$-180\mathrm{ to}+{180}^{\circ }$$\end{document} azimuth range and 0-90∘\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$0-9{0}^{\circ }$$\end{document} elevation range, the proposed method tracks DOA arbitrarily and eliminates the dead zone effect. Additionally, if the estimated azimuth error is within [-90∘,+90∘]\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$[-{90}^{^\circ },+{90}^{^\circ }]$$\end{document}, capturing DOA requires only one 3L-DiLL tracking cycle. Compared with the traditional DiLL, the proposed method is simpler and easier to apply in engineering applications. Simulations verify that 3L-DiLL has a wider tracking range, faster capture speed, and higher tracking accuracy than traditional DiLL schemes.