Research On High Precision GPS Position Receiver Under Multipath Environments

As Global Positioning System (GPS) has found wide applications in more fields, the higher GPS position precision is required, even in the centimeter levels or millimeter levels. Though differential GPS system can mitigate most of errors to improve the position precision, it can not mitigate the error caused by multipath signals. Based on the analysis of the influence of multipath signals on the tracking loop of GPS receiver, this thesis puts emphasis on algorithms for mitigating the multipath effect on the code tracking loop and carrier tracking loop, which consists of the following aspects:1. A mode of multipath signals is obtained, an analysis that the influence of multipath signals on the tracking loop of GPS receiver is made, including the code tracking loop and carrier tracking loop.2. Based on the introduction of the existing multipath mitigation algorithms, a new multipath mitigation algorithm (TK-MPI) is given. It can produce a smaller code tracking error through combining the TK algorithm and the MPI algorithm. Simulations show that the code tracking error using TK-MPI algorithm is 1/20 of that using the tradition receiver, 1/3 of that using TK algorithm.3. A multipath mitigation algorithm for the carrier tracking loop is presented. It uses the least square criterion to estimate the factors of multipath, estimate the carrier tracking error, and then compensate the error. Simulation shows that it estimates the carrier tracking error with a high accuracy.4. Finally, this thesis applies the algorithms above to differential GPS system; Simulation shows that a better position precision is obtained.