Evaluation and simulation of UWB transceiver timebases

The Ultra-Wide Band (UWB) Real-Time Localization Systems (RTLS) usually require high position-fix rates and therefore cannot rely on the conventional but slow Two-way ranging (TWR) approach. Some of the RTLS utilize Time (Difference) of Arival (ToA or TDoA) positioning, in order to achieve hundreds or thousands positioning fixes per second. However, such systems require either precise and robust synchronization of the anchor transceivers, or sufficiently stable clocks for methods referred to as “synchronization-free”. Usually, reasonably priced crystals or TCXOs are utilized as frequency references for the UWB transceivers.

Clock characterization and simulation is necessary to evaluate and tune the synchronization or positioning algorithms without the need of hardware-pulling of the UWB reference oscillators. The simulation also allows testing of the algorithms with defined and repeatable scenarios, potentially featuring extreme clock states, possibly beyond the specified operational envelope.

We present the methodology of evaluation of the UWB timebase characteristics from the transmission and reception timestamps readily available in the widely used Qorvo DW1000 UWB transceiver. The analysis is based on modified Allan Deviation (MDEV) metric; Fig. 1 shows previously acquired data for a pair of DWM1000 modules. Also, Matlab-based timestamp simulation that benefits from the clock characterization will be presented.

Several transceiver pairs will be subject to timebase stability evaluation, including EVB1000 Evaluation board, DWM1000 module with integrated reference oscillator and DW1000 referenced to Caesium standard. A White-Rabbit synchronization will be used to obtain a 10MHz reference signal from the HP 5071A Cs-Clock, the necessary 38.4MHz reference for the DW1000 will be derived using a suitable RF generator with external reference (see Fig. 2).