عنوان مقاله [English]
نویسندگان [English]چکیده [English]
GPS provides accurate measuring of velocity and positioning for marine navigation. Phase Lock Loop (PLL) is used to measure signal carrier phase accurately. Thanks to easy architecture of Costas loop, it has been one of the most-used PLL in GPS software receiver. Phase noise and high dynamic situation effects on PLL designing. To track high dynamic signals, wider loop noise bandwidth is desirable. However, a wide bandwidth allows noises to pass through the loop filter. To reduce the thermal noise, the filter loop with narrow loop noise bandwidth should be designed. But it degrades the tracking loop robustness in high dynamic situation and result in loosing lock. To solve this problem, we have used a Fuzzy Logic Controller (FLC) to tune loop noise bandwidth in an adaptive manner. This FLC is a two inputs and one output system which its membership functions has been optimized with Genetic Algorithm (GA). Carrier phase and its delay version go to FLC as input data. According to changes of input, the loop noise bandwidth changes adaptively. This work has been compared with some traditional methods and the performance of the proposed tracking loop is verified by several simulations.