The TDoA method used in many localization systems requires temporal synchronization to accurately distribute a time reference among the anchors. For this purpose, a wired method was studied, as the architecture of the clock distribution network can affect the accuracy of the signal provided to each anchor. However, instead of connecting each anchor to a common clock source, the clock signal is redistributed in a chain topology to reduce costs and wiring constraints.
The validation of this approach required the development of a node prototype for clock distribution based on the DPLL AD9545, digitally controllable through a microcontroller. The clock distributed by this node was provided to anchors, based on modified EVB1000 boards, in order to accept an external clock source.
The experimental characterization showed that the phase error of the clock thus generated is higher than 9.3% vs. a star topology but still within the design limits. The use of a standard system with wired protocol (IEEE1588-HA, aka White Rabbit) also allowed to simplify the management of the chain topology. However, it required the use of a frequency multiplier (DPLL AD9545) to make the frequency of the clock distributed by the White Rabbit network compatible with that required by the UWB anchors.
An Experimental Characterization of Chain of PLLs for Wired Clock Synchronization of UWB Anchors for Indoor Location
S. Rinaldi, A. Musatti, A. Depari, P. Ferrari, A. Flammini, E. Sisinni. IEEE International Instrumentation and Measurement Technology Conference (I2MTC), Ottawa, Canada, May 16-19, 2022, pp. 1-6. https://doi.org/10.1109/I2MTC48687.2022.9806698
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An Experimental Characterization of Time Synchronization in Multiple UWB Location Cells
S. Rinaldi, A. Depari, P. Ferrari, A. Flammini, E. Mondini, E. Sisinni. IEEE International Symposium on Precision Clock Synchronization for Measurement, Control, and Communication (ISPCS), Vienna, Austria, October 2-7, 2022, pp. 1-6. https://doi.org/10.1109/ISPCS55791.2022.9918442
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