Impact of hardware components on the precision of an UWB positioning system
Examensarbete för masterexamen
Wireless, photonics and space engineering (MPWPS), MSc
The project of establishing the impact of hardware has on the precision of an UWB positioning system was approached with broad scope. Attempting to isolate the influence antennas- and oscillators has on the positioning precision requires a good understanding of the hardware setup for the complete system. An UWB positioning evaluation system was therefore designed and manufactured on PCBs, allowing it to be modified in order to test the system performance with different antennas and oscillators. Oscillators with three levels of frequency stability were chosen to be evaluated. Two patch antennas, one possessing high directivity and one featuring band-reject properties, were designed and manufactured as well. These components effect on precision were evaluated by performing positioning in both Line-Of-Sight (LOS)- and Non-Line-Of-Sight (NLOS) environments using different configurations of the hardware. The results of the tests were then evaluated using several metrics in an attempt to observe differences in the precision of the hardware configurations. Due to limited testing and intrinsic uncertainties of the evaluation system no clear conclusions on the isolated impact of the antennas and oscillators could be made, nevertheless some trends could be identified. The results of the NLOS test indicate that the band-reject properties and increased frequency stability had a positive im- pact on precision. This effect was primarily demonstrated by the significant increase in the number of position estimates acquired, ranging from approximately 7 up to 30 estimates depending on the hardware configuration. The higher directivity antenna generated almost no position estimates in the NLOS test making it less suitable. The LOS tests produced similar results for most hardware configurations with a mean absolute deviation of the position estimates in the vicinity of 0.036 m. A second hardware iteration, testing in a controlled environment and further analysis of the distribution of position estimates are recognized as future improvements. To support this, a lengthy discussion on these subjects and future work is included.
UWB, positioning, indoor, navigation, evaluation system, precision, antenna, oscillator.