| Summary: | 碩士 === 國立臺灣海洋大學 === 通訊與導航工程學系 === 103 === Recently, several researchers have studied a vector tracking loop to obtain an improved tracking performance in GPS receiver.
Traditional GPS scalar tracking loop tracks signals from different satellites independently. Each traking channel measrues the measurements to the navigation processor, which solves for the user’s position, velocity, clock bias and clock drift. In vector tracking loop all channels are processed together in one processor which is typically an extended Kalman filter. Therefore, even if the signals from some satellites are very weak the receiver can track them from the navigation results of the other satellite.
It is a big challenge to the receiver designer that how to track satellite’s signal continuously in degraded signal environment. To achieve higher tracking performance in weak signal environment, the integration time in a GPS receiver has to be increased, but tracking accuracy of a weak GPS signal is decreased by the possible data bit sign reversal every 20 ms to the integration interval.
To solve this problem, a data wipe off algorithm is presented on the basis of pre-detection meathod to detect data bit sign reversal every 20 ms and wipe off. The coherent integration interval is extended over 20 ms. This paper proposes a data wipe off algorithm using carrier phase discriminator to remove the data bit in I and Q correlation values. The algorithm has an advantage to estimate data bit continuously and easily.
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