Abstract
Nowadays, Global Positioning System (GPS) applications are widely spread and affect all aspects of our modern lives. They can be found in many different fields, such as aviation, environment, marine, space, surveying, mapping, and military operations. In military, the GPS is employed in missile guidance, vessels and aircraft navigation, location, communication network timing, etc. The GPS receiver is required to be more and more robust to withstand harsh condition, for example losing signal or jamming. This paper demonstrates the implementation and simulation of an advanced tracking technique that is used in modern GPS receivers - a vector tracking loop. Brief related principles of a GPS receiver are introduced. The principle of traditional tracking loop is shown and compared to the vector tracking loop. An extended Kalman filter is employed as a vector tracking algorithm. The extended Kalman filter uses pseudo range rate, which is computed from both the code and the carrier to constrain the receiver velocity. The acquired results are compared and advantages of the vector tracking algorithm against the traditional tracking loop are presented in this paper, including characteristics of the vector tracking loop.
Highlights
A typical Global Positioning System (GPS) receiver must perform at least four tasks in baseband processing to determine its own position
The simulation model is built in MATLAB using a GPS signal, which is recorded by GNSS software receiver
This paper presented the implementation, simulation and analysis of the vector tracking loop (VTL) characteristic by using the extended Kalman filter
Summary
A typical GPS receiver must perform at least four tasks in baseband processing to determine its own position. These tasks are satellites acquisition, signal tracking, navigation data decoding and navigation equation calculation. In a conventional GPS receiver, each satellite which is revealed at an acquisition stage is tracked in a single channel using a traditional tracking loop or a scalar tracking loop (STL). The advantage of the vector tracking is that the algorithm uses information from the signal integration, and both the position and the velocity of the receiver and the satellites to predict the phase of the incoming signal. In case of one or more satellites being blocked, due to an obstacle or jamming, the algorithm can still track the phase of the signal in that channel by setting information from the other channels – like the position and the velocity of the satellite and the receiver
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