Ultra-High Sensitivity GNSS Signal Acquisition Using Precise Oscillators
Abstract
The 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.
Description
Keywords
Engineering--Electronics and Electrical
Citation
Gowdayyanadoddi, N. (2015). Ultra-High Sensitivity GNSS Signal Acquisition Using Precise Oscillators (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/28544