Lokalisierung von UHF-RFID-Backscatter-Transpondern mit realen und synthetischen Aperturen

This work introduces a novel signal phase based localization method for UHF RFID systems.

The newly developed localization system uses the phase information of the transponder signal. The state of the art in phase based localization requires multiple antenna groups to determine at least two angles of arrival and subsequent triangulation. The newly developed localization algorithm processes all phase information from all antennas simultaneously, severely enhancing the localization result. The achieved accuracy is in the centimeter range and the method can be used with common of the shelf RFID hardware. Furthermore two methods increasing the quality of the phase measurement of a RFID reader have been developed and tested. The measured signal phase also depends on various constant and variable system parameters. A complete overview of these parameters and methods to mitigate possible errors resulting from these has been designed. The influence of the number and the positioning of the antennas on the localization accuracy were investigated to find an optimal system configuration.

Measurements and simulations proved multipath propagation to be the key limiting factor of the localization accuracy. Using these results, it was possible to improve the system layout to reduce the multipath error.

The localization method itself is very flexible. It can be used with synthetic apertures, static antennas and setups combining both. Synthetic apertures with a single antenna only allow for monostatic phase measurements. Multiple antennas can be used for multistatic phase measurements, increasing the number of signal paths and leading to much better localization result. Various system configurations were explored to find the best configuration of any setup.

The newly developed localization system was tested in an indoor environment to determine its performance. Multiple setups utilizing synthetic apertures and one setup with static antennas were investigated. The root mean square localization errors were 0.33 m for synthetic apertures and 1.09 m for static antennas.