Ultra-High Sensitivity GNSS Signal Acquisition Using Precise Oscillators
Multipath phase rate
SubjectEngineering--Electronics and Electrical
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AbstractThe benefits of an ultra stable oscillator are studied in this thesis. The factors that limit the coherent integration period extension given an ultra stable oscillator are first analysed. Coherent integration of over 100 s is demonstrated using such an oscillator and assistance data. It is shown that there is no significant benefit in using precise instead of broadcast ephemeris to perform long coherent integration. It is demonstrated that the position accuracy indoors is limited by multipath errors after the signal sensitivity is resolved. Dealing with weak signal indoors when the signal is subject to several reflections, experimental results show that there is no added advantage in having large and costly antennas instead of small helix antennas. A ray-tracing technique is proposed to study Doppler differences (DD) between LOS and NLOS signals and it is shown how ray-tracing simulation derived DDs can be used as input to multipath mitigation methods. The ray-tracing simulation results are confirmed using a ground multipath model and actual measurements. Using 120 s of coherent integration on GPS signals it is shown that LOS and NLOS signals can be separated in the frequency domain even for a static case, leading to improvement in measurement accuracy. Three possible ways of using ray-tracing based DD as a means of alleviating multipath errors are proposed. Experimental results show that it is possible to increase the probability of LOS and NLOS signal separation in the frequency domain with a few seconds of coherent integration using a slowly moving antenna, as opposed to a few hundred seconds for a static antenna. Positioning results suggest that the moving case has a higher probability of improving accuracy compared to that of the static case.
CitationGowdayyanadoddi, N. (2015). Ultra-High Sensitivity GNSS Signal Acquisition Using Precise Oscillators (Unpublished doctoral thesis). University of Calgary, Calgary, AB. doi:10.11575/PRISM/28544
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