Navigation Solution for Weak GPS Signal

摘要

In the real measure of GPS(Globe Position System), the tracking loop is unstable and usable satellite number for navigation is few because of weak GPS signal and its frequent change in the urban environment. To overcome this shortcoming, GPS receiver can track weak GPS signal in challenge environment by using carrier loop of non-coherent DPLL(Digital Phase Lock Loop). On this basis, this paper does some research on the prediction algorithm of weak signal satellite's send time with ephemeris stored which can improve the usability of the receiver in the city by making the weak signal satellite participate in navigation. Based on the SPIRENT4500 Multi-channel GPS simulator and SEU-GPS, the result of test is provided to give the verification of the algorithm in the end.