Receiver Architectures for Positioning with Low Earth Orbit Satellite Signals

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Sähkötekniikan korkeakoulu | Master's thesis
Small Satellites and Space Instrumentations
Degree programme
Erasmus Mundus Space Master
The field of positioning, navigation, and timing, PNT, with Low Earth Orbit satellites is a rapidly growing sector. It is responding to gaps present in current Global Navigation Satellite Systems, that reside in Medium Earth Orbit, higher above LEO. The GNSS signal strength is decreased in congested, indoor or remote environments. This lends itself to both unintentional and intentional signal interference. Two distinct types of approaches are addressing the challenges with LEO satellites, dedicated, opportunistic and also a combined version. The proximity of a LEO satellite to the user improves signal power at reception. This makes LEO satellites an appealing candidate to improve PNT in weak signal environments. The aim of this thesis is to study how to exploit LEO to maximize PNT benefits for the user. To this extent, the receivers in the user segment are of significance, as they compute the PNT solution. A PNT receiver is composed out of a Radio Frontend, baseband processing, and a navigation processor. The RF receives a satellite's radio signal, the baseband and navigation processing track the signal and compute the PNT solution. The receiver needs to be specified to a given signal in order to perform these functions. Thus, LEO satellite constellations and their signals are studied with respect to their implications on receiver architecture design. Finally, an analysis is presented on receiver architectures for opportunistic and dedicated signals. Both receiver architectures require RFs with large bandwidth, a Software Defined Radio with adjusted tracking and acquisition loops, and a navigation filter. The latter is almost exclusively implemented as a Kalman filter variant.
Praks, Jaan
Thesis advisor
Bhuiyan, Zahidul
navigation, receivers, low earth orbit, positioning
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